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An original partial discharge generated in oil insulation identification methodology based on simultaneously conducted measurements using electrical method, ultra high frequency method and acoustic emission method is presented in the paper. Three different partial discharge model sources as well as measuring instruments commonly applied for partial discharge detection in electrical power transformers are yielded within a laboratory research. Total of 45 scenarios, including proposed spark gap configurations, selected supply voltage levels and UHF frequencies are analyzed during measurements series. Furthermore, form among total of 93 descriptors assigned for every applied partial discharge model source configuration there are 24 proposed as potentially useful for partial discharge identification applications with their 95% confidence bounds. Attempt of discriminative descriptors selection for partial discharge source analysis in on-site transformer applications as well as a proposal of unique descriptors according to every selected spark gap configuration that could be potentially useful for partial discharge identification purposes are the main purpose of the presented paper. The proposed methodology verification on a real life transformer with particular consideration of the selected descriptors potential utility in the fields of partial discharge detection and identification in electrical power industry applications confirmed a proposed methodology usefulness. [ABSTRACT FROM AUTHOR]

• The effect of thermal aging on flashover voltage of unfilled oil/pressboard is evaluated. • The effect of thermal aging on the flashover voltage of nanofilled oil/pressboard is evaluated. • The effect of paper coating on the performance of nanofilled transformer oil is investigated. • The obtained results are validated using finite element method. The service life time of oil filled transformers is mainly dependent on its insulating system; either the mineral oil or oil/paper insulation. Thermal aging of these transformer insulating systems is carried out in this work. Accelerating aging is achieved by inserting the samples in an electric oven at 120 °C for 8 weeks. The effect of aging is evaluated considering different tests. Firstly, the creeping flashover voltage of oil/pressboard is studied considering epoxy coated and non-coated pressboards. Also, the effect of thermal aging on the breakdown voltage of oil/kraft paper insulation as well as transformer oil is carried out. All the aforementioned tests are performed considering unfilled transformer oil (base oil) as well as the same base oil modified by adding 0.08 g/l of MgO nanofiller. The effect of thermal aging considering all the studied cases is discussed and interpreted. Finally, it is found that the epoxy coating and nanofillers significantly affect the performance of oil/paper insulation system. [ABSTRACT FROM AUTHOR]

• Effect of the oscillation on the breakdown characteristics of the oil-impregnated paper under different lightning impulse voltage waves are studied experimentally. • Provide a theoretical reference for the explanation of the on-site impulse withstand voltage test results. • It is suggested that changes on the impulse waveform parameters affect the movement, trap and accumulation of the positive charges ionized inside the oil micro-cavity, causing differences in the breakdown results. Effect of the oscillation on the breakdown characteristics of the oil-impregnated paper under different lightning impulse voltage waves are studied experimentally in this work. IEC60060-3 standard and the waveform requirements of the on-site impulse withstand voltage test are considered, and four lightning impulse waves with different oscillation frequencies and 1.2/50μs standard lightning impulse wave are applied during the experiment. The experimental results show that the breakdown voltage under 1.2/50μs impulse is lower than that under the oscillating impulse. Under the oscillating waves, as the oscillating frequency increases, the number of breakdown points distributed at the peak of the non-first cycle increases, the minimum breakdown time gradually shortens, and the breakdown voltage shows a decreasing trend. The possible breakdown process of paper and the influence mechanism of different waveform parameters are discussed in detail. The explanation could be that changes on the impulse waveform parameters affect the movement, trap and accumulation of the positive charges ionized inside the oil micro-cavity, causing differences in the breakdown results. This study deepens the understanding of the breakdown mechanism of paper from the perspective of the waveform parameters effect and can provide a theoretical reference for the explanation of on-site impulse withstand voltage test results. [ABSTRACT FROM AUTHOR]

The electric power sector is experiencing a rapid shift towards renewable energy resources. To accommodate this transition, the transmission system requires significant upgrades. Although enhancing grid capacity through transmission network expansion is always a solution, it can be very costly and requires a protracted permitting process. Grid-enhancing technologies (GETs) encompass a broad range of hardware and software tools that enable reconfiguration of the transmission grid and adjustment of its parameters. The proliferation of such technologies enhances transfer capability over the current transmission network, thus reducing the need for grid expansion. This paper offers a comprehensive review of grid-enhancing technologies. The paper discusses definitions of transmission flexibility and presents methods that are developed to quantify grid flexibility. The paper offers a comprehensive review of an extensive range of grid-enhancing technologies, including both principles of operation and state-of-the-art developments. Environmental impacts of grid-enhancing technologies, including renewable energy curtailment and carbon emission reduction, are also discussed. In addition to technical aspects of grid enhancing technologies, the paper also reviews the literature on the incentive challenges facing GETs adoption and efficient. Overall, the paper offers a comprehensive review of the advancements in grid-enhancing technologies, discusses the remaining critical challenges, and identifies directions for future research. • Grid-enhancing technologies (GETs) are necessary for the future grid. • GETs can enhance the transfer capability up to 50% over the existing grid. • While some GETs rely on mature technology, industry adoption remains rather limited. • GETs integration within energy management systems faces modeling challenges. • Current market and regulatory structures provide little to no incentive for adoption and efficient operation of GETs. [Display omitted] [ABSTRACT FROM AUTHOR]

• A method to correlate indirect lightning strokes and flashovers is presented. • The method focuses on the ratio between current peak and distance from the line. • The results provided by Rusck's and Darveniza's formulas and LIOV code are compared. • The minimum collecting area for calculating the lightning performance is addressed. Lightning location systems provide an estimation of both lightning current peak amplitudes and stroke locations, which are useful information to correlate lightning strokes and faults in power distribution networks. The paper presents a novel method for assessing the correlation between a lightning-induced flashover and the lightning current-peak-to-distance ratio of indirect lightning events. This is motivated by the consideration that a minimum threshold/value of the ratio between current peak and stroke distance from the line must be reached for an insulation flashover to occur. The proposed procedure uses existing equations and models that relate induced voltage peak amplitudes, distance, current peak and other parameters. Specifically, the paper compares the results predicted by Rusck's and Darveniza's formulas with those provided by the more detailed model implemented in the LIOV code. It is found that a minimum lightning current-peak-to-distance ratio must be exceeded to trigger an insulation flashover and that Rusck's and Darveniza's formulas may be too conservative in estimating such a threshold value. The paper provides guidelines for properly estimating the minimum collecting area around the line including all hazardous events, as this information is essential for calculating the lightning performance of a power distribution line using a Monte Carlo-based approach. [ABSTRACT FROM AUTHOR]

This paper addresses a comprehensive review on various adaptive grid-following inverter control schemes developed for enhancing the power quality in renewable energy generation systems (REGS). The grid interfacing inverter with various adaptive control schemes has been well researched in recent years and their performance has been found with better characteristics compared to the conventional control schemes. Better fundamental component separation (FCS), dc offset rejection, grid synchronization, amplitude tracking, frequency tracking, phase angle estimation, and low complexity are the few silent features of the adaptive-based control schemes. This survey is very useful for researchers who are working on power quality, AC and DC Microgrid, grid-connected inverter control, multilevel inverter, power electronics, and other related research areas to select the suitable controller for grid interfacing inverter. This paper also focuses the power quality issues, basic standards, power quality monitoring schemes, and solutions. Moreover, power quality improvement techniques by using the power quality conditioners with adaptive control schemes are discussed in the paper. Finally, an extensive comparative study of the recently developed control techniques is performed to select a suitable controller in terms of better FCS, dc offset rejection, grid synchronization, amplitude tracking, frequency tracking, phase angle estimation, and low complexity for grid-following inverter in REGS applications. [ABSTRACT FROM AUTHOR]

• The improved thermal circuit model proposed in this paper exhibits a relative error of approximately 1.5 % compared to the results obtained using the finite element method. In comparison to the IEC thermal circuit model, the maximum discrepancy is 123A, with a maximum relative difference of 12 %. • The variation in seawater temperature, salinity, and pressure adjusts the thermal parameters of seawater, thereby modulating seawater thermal resistance and convective heat transfer coefficient, consequently influencing the current-carrying capacity of the submarine cable. Hence, laid cables are most affected, buried cables in less impact. • Without considering the variability in seawater properties, the calculated current-carrying capacity tends to be higher than the actual values, with a maximum error of approximately 5.5 %. Temperature has the most significant impact, accounting for 3.3 %, while the influences of salinity and pressure are around 1.1 %. The IEC 60287 standard, when calculating the steady-state current-carrying of DC submarine cables, does not take into account the influence of seawater property variations on changing the heat transfer efficiency of seawater, thereby affecting the current-carrying capacity of the cable. resulting in deviations in the calculated ampacity results. This paper considers the influence of seawater heat transfer characteristics on cable heat dissipation efficiency based on heat transfer theory, and Proposes an improved thermal circuit model for submarine DC cables that takes into account variations in seawater properties. Taking the example of a 160 kV submarine XLPE cable, the current-carrying capacity results of the improved model have an error of no more than 1.9 % compared to finite element simulation results. Under identical environmental conditions, the maximum deviation between the improved model and the IEC thermal circuit model is 123A, confirming the necessity of considering variations in seawater properties in the improved thermal circuit model. The seawater property variations studied in this paper include changes in seawater temperature, salinity, and pressure. If the impact of seawater property variations on submarine cable current-carrying capacity is not considered, the obtained current-carrying capacity results are higher, with a maximum error of 5.5 %. Among these variations, temperature has the most significant impact, with an error reaching 3.3 %, while salinity and pressure have relatively smaller impacts, with errors of 1.1 % each. [ABSTRACT FROM AUTHOR]

In this paper, the authors have adapted existing thermal models for the calculation of conductor temperature for use in electrical distribution systems for railway applications in multi-train environments. For this purpose, the authors have used existing standards such as IEEE 738 for overhead lines and have proposed a resolution methodology based on the difference equation model for cables. The authors have opted for a simplified method since the priority in this case is the resolution in systems with multiple stations, lines, and trains. For this same reason, they have chosen to decouple the electrical and thermal calculations so that the electrical variables calculated through load flows constitute the input to the thermal calculation problem. The paper reviews the existing formulation and proposes models for specific use in railway applications in a multi-train environment. A detailed analysis of the results obtained in a real case study is presented as a validation element. • Thermal model of DC conductors applicable to overhead wires and cables. • Adaptation of the model for the use in electric railway distribution system. • Application of the model to be used in a multi train environment. [ABSTRACT FROM AUTHOR]

This paper introduces an advanced co-simulation environment developed to assess the cyber resilience of active distribution grids, with a focus on demand side management concepts. By integrating energy systems, communication networks, and operational technologies, the framework evaluates the impact of cyber threats on the functionality and stability of distribution grids. The focus of this paper is the newly introduced communication simulator, which provides a solution to simulate the communication flow between the different actors with a generalised representation of the protocols used. This approach enables the investigation of system architectures without requiring the specific implementation of, for example, protocol stacks. Utilising the STRIDE framework for comprehensive threat modelling, the framework then simulates cyber–physical disruptions in an abstract manner, thereby allowing for a nuanced understanding of potential vulnerabilities and resilience strategies. A case study demonstrates the application of the framework, highlighting its potential to enhance grid resilience through strategic simulation of various cyber attack scenarios. • Co-simulation to investigate the cyber resilience of demand side management. • Flexible solution for attack simulation based on threat modelling concepts. • Case study investigating a resilience enhancing fallback mechanism. [ABSTRACT FROM AUTHOR]

• Uncertainties in the power system make its state unpredictable. • Power system predictability can be improved by optimal tap setting of transformers. • Increasing predictability helps the operator to make decisions with high assurance. • power system predictability can be improved without considerably affecting losses. In recent years, renewable energy sources (RESs) such as wind turbines (WTs) have received much attention in both the operating and planning of power systems. These sources have caused many uncertainties in the operation of power systems due to their unpredictable nature. Mentioned uncertainties besides load demands uncertainty, and possible failures in power system components, make the system state unpredictable. The operational decisions are completely challenging in these situations. Any efforts to increase the network operator awareness from the system state will be completely valuable for making accurate decisions. This paper tries to increase the predictability of the power system state through optimal regulating of the voltage setpoint of automatic tap changer transformers and generators besides the reactive power of shunt capacitors. However, conventional objectives such as decreasing losses are considered, simultaneously. This paper uses the K-medoids data clustering method to evaluate the effect of uncertainties. Also, the correlation between input uncertain variables is considered and handled by the Cholesky decomposition technique combined with the Nataf transformation technique. The multi-objective optimization problem is tackled using an improved version of the non-dominated sorting genetic algorithm (NSGA-II). To ensure for validity of the results, studies are repeated using the multi-objective particle swarm optimization (MOPSO) algorithm as another evolutionary-based method. The proposed approach is applied to the IEEE 14 and 30 bus standard system. The results showed that the predictability of the power system can be considerably increased while keeping the losses approximately at its minimum amount. [ABSTRACT FROM AUTHOR]

• Importance and challenges of relay coordination in Microgrid. • Overview of different adaptive schemes opted for relay coordination. • Different optimization techniques which have been used for the calculation of relay settings. • Evolvement of algorithms from conventional to Hybrid methods which combines two different metaheuristic methods to solve a complex, non- linear optimization problem in an efficient way for optimized relay coordination. • Future directions of research for further modifications possible in Algorithms are stated at the end. Concept of microgrids (MGs) have gained significant attention in order to enhance the resilience and efficiency of modern Power Systems. MG offers bi-directional power flow so an effective protection and control becomes a vital requirement to ensure the reliable operation of MGs. Relay coordination being an integral part of the protection system, plays a critical role in prevention of power disturbances and equipment damage due to the presence of bi-directional power flow. This review paper focuses on the optimization of relay coordination in MGs, and highlights the importance of adaptive and intelligent approaches involved for the efficacy of MG operation. This paper overviews different schemes used to adapt while determining the DOCRs settings with different contingencies considered. The paper depicts the key challenges associated with relay coordination in MGs; varying fault currents, and bidirectional power flows. To overcome these challenges, recent researches have explored advanced techniques that includes intelligent algorithms to operate on collected real-time data. Additionally, the impact of communication technologies for relay coordination in real-time has been discussed for Grid connected and Islanded mode of operation. This review covers a wide range of optimization methods such as; Traditional, Meta-Heuristic, and Hybrid algorithms, which allows adaptive and reliable protection schemes during different modes of MG operations. [ABSTRACT FROM AUTHOR]

Power system protection is crucial for maintaining the stability and reliability of the electricity grids and preventing costly disruptions. Conventional protection devices operate on pre-defined fixed settings and are no longer sufficient to ensure system stability and reliability in today's dynamic and complex electricity grids. With the rise of distributed renewable energy sources and the ability to reconfigure network topologies, an adaptive protection scheme has become necessary to quickly respond to changes in network configuration. This paper provides a state-of-the-art review of research efforts in the field of adaptive protection schemes, including the use of the IEC 61,850 protocol to incorporate automation opportunities. The IEC 61,850 protocol provides a standardized approach for communication between protection devices and the overall control system, enabling more efficient data sharing and reducing the need for manual intervention. This review paper is helpful for researchers, engineers, and policymakers involved in the development and implementation of adaptive protection schemes, enabling them to make informed decisions about the most effective strategies for ensuring the stability and reliability of modern power systems. [ABSTRACT FROM AUTHOR]

• In response to the reviewer's valid concerns, we have introduced a clear and comprehensive note in the paper, elucidating our deliberate departure from the conventional theoretical approach traditionally embraced by the industry, which predominantly centres around the lightning current sharing rule (50:50). • This advanced modelling approach stands out for its capability to meticulously scrutinise a multitude of parameters and explore diverse what-if scenarios. By doing so, we not only elevate the precision and depth of our analysis but also broaden the scope of our investigation to encompass a more comprehensive range of potential factors and conditions. • The focus of our paper is primarily on emphasising the approach to mitigate the risk of voltage stress across insulation flanges, particularly examining the influence of connecting lead lengths. It's crucial to interpret the absolute values in the results with care, as they are indicative of an extreme scenario involving high impulse current (200 kA) and steepness (20 kA/μs). While these values represent an extreme case, the main takeaway from our calculations remains valid. There is a quantifiable reduction in the range of 34 % when implementing the proposed mitigation measures, signifying a substantial contribution to risk mitigation. • We have incorporated a dedicated section into the paper, labelled as 4.1 sensitivity analysis. Insulating flanges serve as crucial components, strategically positioned between two segments of a pipeline to ensure effective electrical isolation. These elements play a vital role in facilitating the optimal performance of the cathodic protection system of buried pipeline networks. Moreover, an isolating spark gap is commonly integrated between adjacent pipeline sections to mitigate the stress voltage induced on the insulating flange during lightning strike events.. Despite this protective measure, certain scenarios may arise where the voltage drop across the isolating spark gap's connecting cables surpasses the insulating flange's dielectric strength, leading to undesirable failures. The magnitude of this voltage drop is contingent upon various factors, including the parameters of the incoming surge as well as the length of the connecting cables. In this paper, we present both straightforward theoretical calculations and intricate modelling techniques that can be employed to assess the lightning risk associated with the insulating flanges of pipelines that incorporate isolating spark gaps. [ABSTRACT FROM AUTHOR]

• An analytical criterion to examine the transient synchronization stability of the island 100 % RPG system connected to the sending-end of Zhangbei MTDC network is proposed. • The paper reveals that excessive reactive current generated by the wind farm may cause the loss of synchronization of the island 100 % RPG system during the fault. • The current limiter's parameters in the grid-forming MMC and the current injections of the wind farm during the fault should be coordinately determined in order to maintain the transient synchronization stability of the island 100 % RPG system during the fault. This paper examines the transient synchronization stability (TSS) of an island 100 % renewable power generation (RPG) system that is connected to the Zhangbei multi-terminal direct current (MTDC) system. A large-signal model of the system is derived, based on which an analytical criterion for evaluating the TSS of the system is proposed. From the proposed TSS criterion, the current injection of the RPG, the current injection of the MMC, the parameter settings of the PLL, and the fault ground resistance and distance are identified and examined as four key factors affecting the system TSS. In addition, analysis in the paper highlights the importance considering the reactive current generated by the RPG during the fault, because excessive reactive current may causes the instability of the island 100 % RPG system. To demonstrate and evaluate the proposed TSS criterion and the analytical conclusions made, study cases to examine the TSS of the island 100 % RPG system connected to the Zhangbei MTDC are presented in the paper. [ABSTRACT FROM AUTHOR]

• This research paper proposed a novel computational technique for evaluation of the corona generated ionized electromagnetic field environment which initiates serious ill health environment under EHV/UHV DC transmission lines. • The proposed new computational technique was developed by modelling the dynamic behavior of the corona discharge phenomenon using gas ion bimolecular collision theoy concept which offers program less simple equations. • This developed computational technique offers unique equation solution which estimates corona generated ionic currents for any existing and upcoming HVDC transmission lines. This new computational analysis offers economical benefits to the line design engineers. • Actual experimental investigations are carried out at extra and ultra high potential levels to validate the accuracy of the proposed computational technique. • The proposed computational technique offered high computational accuracy compared to other techniques which are proposed elsewhere in the world and the computed results shown exact measured values. Corona on UHVDC transmission line conductors initiates corona power loss and the inevitable ionic current flow environment at ground level. To limit this substantial flow of ionic current at ground levels, it is necessary to establish an appropriate line design configuration, including the diameter of the line conductor and the height level above the ground. It is a tedious and expensive process to establish this appropriate line design solely based on experimental findings. Hence, the computational based numerical analysis with the support of final experimental validation aids in arriving at a safe and optimal transmission line design dimension configuration. Thus, the ionic current flow environment of UHVDC transmission lines may be characterized by ionized space charge density, ionic current flow, and electrical field distribution. To estimate this ionic current flow, it is necessary to estimate the ionized space charge density in the ionization region, which incorporates the solution of the Poisson's equation. It is intricate to solve Poisson's equation with known boundary conditions: as ionization process depends on the atmospheric parameters also. Multiple computational techniques are developed to estimate the corona generated ionic current environment under the HVDC lines by waiving these atmospheric parameter effects and claims the lack of computational accuracy. In this paper, the unipolar corona equation, usually called Poisson's equation was solved by estimating the space charge ion density using the concept of gas bimolecular collision theory. The gas bimolecular collision theory inculcates the procedure to estimate the collisional reaction rate constant between the gas molecules at given atmospheric temperature and pressure parameters. Therefore, this paper developed a unique equation solution for the estimation of transition of the ionic current magnitudes at known atmospheric temperature and pressure ambient conditions. This unique equation solution prevents the multiple actual testing procedures offers to obtain safe and optimal line design dimension configurations. Multiple experimental studies are carried out up to ± 900 kV to compare the computed results in the outdoor and indoor climatic conditions at the ultra-high voltage laboratory, CPRI. Also, the computed results are compared with the results published in the literature. Based on the comparison of results, the developed computational technique exactly matches the experimental results and claims improved accuracy compared to other computational techniques. [ABSTRACT FROM AUTHOR]

• A new flexible lexicography method for multi-objective optimization problems in DNR is introduced. • The proposed method increases the flexibility of the operator to better control the electrical indices of the network by distribution network reconfiguration. • The effect of nonlinear load and harmonic DG injection in DNR is investigated. • The effect of unbalance in line, loads, and single-phase DGs in DNR is studied. • The distribution system operator should consider network unbalance in the reconfiguration to more reduction of power losses. Reconfiguration is a low-cost method to reduce power loss in distribution network (DN). Harmonics and unbalancing cause additional losses in DNs. Therefore, it is necessary to consider these two factors in distribution network reconfiguration (DNR). In this paper, the effect of reconfiguration in two harmonic polluted medium and large scale DN is evaluated. In addition, the effect of harmonic injection of distributed generation (DG) is studied. Moreover, the effect of reconfiguration in unbalanced DN in the presence of single-phase DGs is investigated, and it is concluded that distribution system operator (DSO) should consider network unbalance in DNR to more reduction of power losses. Furthermore, a new flexible lexicography method is introduced to solve multi-objective problems, especially in DNR. In the proposed method, the DSO determines the priority of each goal in comparison to the other goals, instead of using weighing factors of them. This method is effective for power quality goals which cannot be illustrated as cost function. In this paper, validation of the proposed method in IEEE 69 bus and 95 bus practical harmonic polluted DN and 25 bus unbalanced DN in presence of three-phase and single-phase PVs are investigated. Results show the effectiveness of the method in increasing the flexibility of DSO in DNR to improve power quality goals such as harmonics and unbalance, as well as reduce power losses. [ABSTRACT FROM AUTHOR]

This paper studies a privacy-preserving distributed state estimation (SE) problem in smart grid systems with an AC power flow model. To enhance the precision of SE, a sensor data fusion approach is employed to integrate the sampled data from supervisory control and data acquisition (SCADA) and phasor measurement units (PMUs). Then, through iterative information exchange among local and neighboring areas, all interconnected areas can achieve consensus on unbiased estimations while avoiding the issue of excessively large data dimensionality caused by centralized data acquisition. In addition, the proposed approach combines with the average consensus algorithm, significantly reducing the computational burden and enabling real-time distributed SE, and the incorporation of differential privacy further mitigates potential privacy leakage risks during the information transmission process. Simulation results on IEEE 14-bus and IEEE 118-bus systems demonstrate that the proposed approach not only achieves excellent estimation accuracy but also significantly reduces the convergence time, while maintaining enhanced the capability of privacy-preserving. • The model developed in this research is more closely with the operational patterns of real-world systems. • The distributed algorithm proposed in this paper does not rely on local observability or a central coordinator. • The proposed internal-merger and external-modification (IMEM) algorithm significantly reduces the number of iterations during simulation. • Differential privacy further enhances the security of local private data. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy sources (RESs) in the global power grid is transforming the traditional landscape of power generation. This shift from rotating synchronous generators to inverter-based RESs presents a unique challenge in maintaining the grid frequency stability due to the decline in system inertia. The stochastic nature of power generation, load demand, and grid inertia poses further challenge in ascertaining the frequency stability. This paper addresses this challenge by proposing indices that assess the sensitivity, resiliency, and permissibility of grid frequency under different RES penetration levels. These indices provide valuable insights into the stability of power grids and highlight the increased vulnerability of grid frequency to disturbances with increased RES integration. Monte Carlo simulation (MCS) is used to incorporate intermittencies and uncertainties associated with the load demand and RES generation. Furthermore, the paper presents a methodology to determine the required level of inertial support for maintaining the frequency reliability in the presence of RESs. The application of the proposed stability indices and methodology in a case study, which utilizes a modified IEEE 39-bus test system emulating a real-world power grid with diverse load types and RESs, validates their effectiveness. • Introduced indices for grid frequency stability in varying RES conditions. • Proposed a daily grid stability framework considering RES/load uncertainties. • Methodology presented to assess inertial support needs with RES integration. [ABSTRACT FROM AUTHOR]

This paper presents an original energy management methodology to enhance the resilience of ship power systems. The integration of various energy storage systems (ESS), including battery energy storage systems (BESS) and super-capacitor energy storage systems (SCESS), in modern ship power systems poses challenges in designing an efficient energy management system (EMS). The EMS proposed in this paper aims to achieve multiple objectives. The primary objective is to minimize shed loads, while the secondary objective is to effectively manage different types of ESS. Considering the diverse ramp-rate characteristics of generators, SCESS, and BESS, the proposed EMS exploits these differences to determine an optimal long-term schedule for minimizing shed loads. Furthermore, the proposed EMS balances the state-of-charge (SoC) of ESS and prioritizes the SCESS's SoC levels to ensure the efficient operation of BESS and SCESS. For better computational efficiency, we introduce the receding horizon optimization method, enabling real-time EMS implementation. A comparison with the fixed horizon optimization (FHO) validates its effectiveness. Simulation studies and results demonstrate that the proposed EMS efficiently manages generators, BESS, and SCESS, ensuring system resilience under generation shortages. Additionally, the proposed methodology significantly reduces the computational burden compared to the FHO technique while maintaining acceptable resilience performance. • Proposing a resilient EMS utilizing BESS and SCESS for modern ship power systems. • Proposed EMS tackles practical ESS constraints (SoC balancing, SCESS SoC priority). • RHO enhances ESS-GEN coordination, addressing real-time, large-scale challenges. [ABSTRACT FROM AUTHOR]

The protection of high-voltage direct current (HVDC) grids is a crucial aspect in ensuring the reliable and efficient operation of modern electrical energy transmission systems. The high amplitude and rate of change of fault current as well as the presence of multiple paths for fault current contribution of voltage-sourced converters make the protection of HVDC grids with meshed configuration a challenging task. This paper develops a protection scheme for these grids that has three modules: (i) low-resistance fault detection module based on the amplitude of the voltage across the current limiting reactor (CLR) at the line terminal, (ii) high-resistance fault detection module based on quantifying the severity of the CLR voltage signal change, and (iii) fault classification module. No need for communication links increases the reliability and operating speed of the proposed scheme. Moreover, severity measurement based protection increases the sensitivity of fault detection. The ability to faulty line identification in the meshed configuration verifies the selectivity of the proposed scheme. In addition, its robustness is verified due to low susceptibility to measurement noise, DCCB operation, AC fault, various CLR sizes, and power reversal. Several pole-to-pole and pole-to-ground fault scenarios with various fault resistances at different fault locations are conducted to verify the reliable performance of the proposed HVDC protection scheme. • The paper develops a single-end protection scheme for VSC-HVDC grids. • It is based on processing the voltage across current limiting reactors (CLRs). • It can detect both severe and high-resistance fault conditions. • It is robust to the measurement noise, DCCB operation, AC fault, various CLR sizes, and power reversal. • It does not require a high sampling rate. [ABSTRACT FROM AUTHOR]

• A distribution network restoration model based on multi-source collaboration is proposed. • The risk of transportation route is considered in the dispatching process of mobile power sources. • A new multi-objective optimization method, ripple diffusion algorithm, is used. With the frequent occurrence of sudden natural disasters, there are more and more disaster events in distribution network, so the research on improving the resilience of distribution network after disaster has attracted increasing interest. Considering the diversity of emergency recovery resources in post-disaster distribution networks, this paper proposes a power grid resilience enhancement model based on multi-source coordination strategy, which comprehensively considers the synergistic effects of distribution line topology, distributed generator(DG) equipment and mobile power sources(MPS). In order to solve the problem that the scheduling strategy is difficult to implement due to the influence of transportation roads, this paper considers the risk problem of transportation lines on the basis of transportation distance factors, and uses ripple spreading algorithm(RSA) to calculate the Pareto front of transportation routes, which is used as an alternative set of transportation routes for MPS equipment. Finally, the IEEE 33-node model is used to verify the effectiveness of the proposed model, the importance of considering transport road risk for actual resource scheduling, and the advantages of RSA in terms of speed and accuracy. The results show that the model can effectively solve the optimal scheduling strategy according to the decision maker's risk preference. [ABSTRACT FROM AUTHOR]

• The paper presents a new method to detect cyberattacks from power quality disturbances in smart digital substations • The method uses wavelets as the signal processing tool and the deep learning to extract the salient features of the cyberattacks • The method uses only three features among the physical and the network features to detect the cyberattacks after representing them in the time-frequency domain • The proposed approach was applied on two publicly available dataset from an SDS • The results have shown that the proposed approach was effective to detect and classify cyberattacks from power quality disturbances with 100% detection accuracy • Furthermore, the proposed approach has been experimentally tested in real-time using OPAL-RT. Smart Digital Substations use communication networks to exchange the information among its components to perform monitoring and control, which makes such components prone to cyber-security threats. The presence of power quality disturbances may add complexity to the problem of detecting such cyberattacks as some of these power quality disturbances behave in a similar manner to some attacks. In this paper, a novel approach that detects cyberattacks from power quality disturbances and normal operation is developed. The proposed approach uses only three out of the twenty-nine features to detect such cyberattacks. The proposed approach uses the continuous wavelet transform to represent such features in the time-frequency scalograms, which are then fed to a convolution neural network for detecting cyber-attacks and power disturbances in IEC-61850 substation systems. The proposed approach has been tested on three datasets from substation test systems as well as in real-time using OPAL-RT. The results have shown that the proposed approach was effective in detecting the cyberattacks from power disturbance and normal operation with a detection accuracy of 100% in simulation environment and 99.45% in real-time using OPAL-RT. [ABSTRACT FROM AUTHOR]

• The optimal activation of balancing resources reduces the costs for balancing energy. • The transmission network constraints should be considered in regional balancing. • The regional integration of balancing markets reduces the balancing costs. • The increased RES penetration increases the need for balancing energy. The objective of this paper is to introduce an approach for enabling optimal activation of balancing energy resources within a regional balancing market. In order to take into account the constraints from the transmission network, the paper proposes a modified technique for optimal power flow calculation. This novel approach results in a more effective usage of transmission network capacities during reserve activation on a regional level compared to the conventional Common Merit Order List (CMOL) approach, which only considers the available cross-zonal transmission capacity (CZC) and disregards the physical power flows. The paper provides details on a procedure that includes simulation of electricity markets, as well as simulation on imbalances in the system. The methodology is used for evaluating the proposed approach on an IEEE test system comprising of three zones. The paper shows a significant reduction of balancing costs by implementation of regional balancing market it also investigates and shows the impact of the increased RES penetration to the amount of needed balancing energy in the system. [ABSTRACT FROM AUTHOR]

• The simulation model of cable in duct bank with mixed filler was built. • The improved thermal model of cable in duct bank with mixed filler was proposed. • The accuracy of the improved method was verified by the real cable test. • The cable ampacity improvements of using different mixed fillers were discussed. • The basis for determining the performance of mixed filler was provided. Duct laying is a common cable laying way for the case of not meeting excavation conditions. However, due to the slow air flow rate in the duct, the cable section laying the duct becomes one ampacity bottleneck. Backfilling the duct with the mixed filler of high thermal conductivity material and phase change material is an effective method to solve the problem. In this paper, the simulation models of cable in ducts with backfilling the mixed filler were used to analysis the effect of relative position of cable and duct on temperature distribution and guide the thermal modeling of external environment. Then, the thermal model of cable in duct was conducted and the layered method was adopted to optimize the model. The real cable experiment was designed to verify the accuracy of proposed model. The improvement effect of mixed filler with different thermal conductivity and phase transition region on the cable ampacity were discussed by using the proposed model. The investigations in this paper show that the use of mixed filler material can have a great contribution to ensure the safe operation of cable in duct. [ABSTRACT FROM AUTHOR]

• The ice-shedding labels are introduced by considering 12 typical ice-shedding modes. • The output datasets are built by feature extraction. • Four prediction models for response characteristics parameters of isolated-span transmission lines are built. • Proposed prediction method provide guidance for the maintenance of the isolated-span transmission lines in heavy ice areas. In response to the problem of insufficient research on the prediction for response characteristics parameters of isolated-span transmission lines under various ice-shedding modes, study on the prediction for ice-shedding response parameters of isolated-span overhead lines is conducted in this paper based on finite element simulation and machine learning. Firstly, the finite element simulation model of isolated-span overhead line is established and verified. Seven model input parameters are determined by considering 12 typical ice-shedding modes and ice-shedding labels are introduced. Six key output parameters reflecting the electrical and mechanical characteristics of the ice-shedding transmission line are obtained by feature extraction. Secondly, the output parameters of the ice-shedding transmission line under different input parameter conditions are obtained by using the finite element simulation method. A total of 1400 sets sample data are constructed. Then, four typical regression prediction models of BP (Back Propagation Algorithm), RBF (Radial Basis Function Algorithm), SVM (Support Vector Machine Algorithm) and RF (Random Forest Algorithm) are established to predict the key output parameters of ice-shedding transmission lines. Finally, the optimal prediction model for ice-shedding response characteristics parameters of isolated-span transmission lines is selected and the application effect is analyzed by actual ice-shedding case. It is found that the RF prediction model is the optimal prediction model among the four regression prediction models. The prediction method for ice-shedding response characteristics parameters of isolated-span transmission line proposed in this paper can accurately predict the response characteristics parameters of ice-shedding transmission lines which can provide some references for the safe operation of isolated-span transmission lines in heavy ice areas. [ABSTRACT FROM AUTHOR]

• A method to jointly estimate the state variable and line parameters in a three-phase distribution network. • Line parameter estimation is framed as hybrid algorithm of unconstrained non-linear optimization with Multi-run optimization. • Compared to the augmented vector state and line parameter estimation method. • Proposed method is capable of handling measurement errors. • Non-PMU method. The line parameters of the distribution feeder play a crucial role in the operation and analysis of the distribution system. In many developing nations, precise knowledge of these parameters are often lacking. This paper proposes a method for accurate estimation of feeder parameter along with the system states using a decoupled state and line parameter estimation technique. This method does not need a phasor measurement unit (PMU) installed at the feeder terminals. The paper also presents a comparison of decoupled method and the augmented vector state and line parameter estimation method. The proposed methodology has been verified through comprehensive case studies conducted on IEEE 123 bus three-phase distribution system. Through detailed simulation studies, it is observed that the proposed methodology is superior to the augmented vector method both in terms of accuracy and computational time. [ABSTRACT FROM AUTHOR]

• This paper introduces a graph spectral clustering and visualization method based on similarity network fusion analysis. • The proposed framework exploits the network structure to jointly analyze system dynamics and network connectivity, a feature often absent in purely data-driven analysis techniques. • Due to its analytical structure and simplicity, it facilitates the integration or fusion of multiple types of measurements, leading to the identification of reduced-order models. • Combined with the graph community structure concept, the proposed framework facilitates the identification of significant buses and transmission branches. • Application studies investigate the integration, analysis, and visualization of data in a practical test system. Integrating data from different types or modalities poses an increasingly significant challenge in system monitoring. This paper presents a method for graph spectral clustering and data fusion rooted in the concept of similarity network functions. The proposed approach aims to identify a reduced-order model (a coarse-grained representation) and determine influential variables in system dynamics, streamlining the integration of diverse data types. This is accomplished through a systematic dynamic framework for data fusion formulated based on diffusion geometry and Laplacian embedding of similarity networks. The statistical properties of Markov processes are leveraged in this approach to construct a similarity network or graph for each data type or information to gain a more comprehensive understanding of relationships and patterns within the underlying data. Integrating the proposed approach with the concept of graph community aids in identifying crucial buses for monitoring and analysis. The paper discusses practical considerations related to the application of spectral analysis techniques and presents improvements upon previous work. It also highlights promising methodologies for robustly addressing the challenges posed by investigating the multimodal attributes of data. Detailed simulation studies conducted on a 14-machine, 58-bus test system illustrate the effectiveness of diffusion-based similarity network function techniques. [ABSTRACT FROM AUTHOR]

• Employing a global optimization technique to solve nonconvex economic dispatch. • Binary zig-zag and general integer zig-zag formulations of the economic dispatch. • Outperforming earlier methods in solution quality, robustness, and efficiency. To solve economic dispatch (ED) with nonconvex nonlinear generation cost functions, this paper adopts a global optimization technique where piecewise linear approximation (PLA) functions replace the nonlinear functions. However, a problem with this technique is that the PLA model requires incorporating many discrete variables into the optimization model, which may render the model computationally expensive. This paper presents two efficient representation techniques of the PLAs, which scale logarithmically, including binary zig-zag (ZZB) and general integer zig-zag (ZZI). We replace the nonconvex cost functions in the ED with their PLAs and obtain an alternative ED formulation where two logarithmic techniques model the PLAs. Then, one can efficiently solve the alternative ED model with the standard branch-and-cut/bound-based algorithms to the desired optimality gap. To verify the techniques' efficacy, we consider test systems having 13, 38, 40, 80, and 160 units. The numerical evaluations show that the logarithmic techniques presented can yield high-quality optimal solutions in less than 2 seconds in the considered cases, illustrating the techniques' efficiency. [ABSTRACT FROM AUTHOR]

• Investigate the challenges posed by voltage instabilities, such as sag/swell events and harmonics, in power systems. • Propose an innovative approach by integrating a DVR unit with a PV system to mitigate power quality issues. • Optimize the control strategy using a GSO tuned PID Controller based on the Versatile control on Synchronous Reference Frame (VCSRF) theory. • Conduct performance analysis of the proposed controller in different scenarios, including deep balanced, balanced, and unbalanced sag and swell conditions. • Evaluate the THD reduction achieved by the proposed DVR system compared to systems employing various controllers through numerical analysis. • Execute practical implementation of the proposed system and analyse its THD performance to validate its real-world applicability. This paper addresses the paramount issue of maintaining optimal power quality in power system networks to ensure reliable operations. The paper introduces an innovative solution that effectively mitigates power quality challenges stemming from disturbances like voltage sag/swell events and harmonics. The approach combines a Dynamic Voltage Restorer (DVR) unit with a Solar PhotoVoltaic (PV) system, incorporating advanced control strategies. Leveraging the Glowworm Swarm Optimizer (GSO) Tuned Proportional-Integral-Derivative (PID) Controller and the Versatile Control on Synchronous Reference Frame (VCSRF) theory, our system achieves exceptional results. Extensive MATLAB/Simulink simulations demonstrate the superiority of the proposed DVR system over traditional PID, GA, PSO, and SSA controller-based DVR systems. Notably, our approach achieves significant reductions in Total Harmonic Distortion (THD), with reductions of 5.27 % (PID), 3.14 % (GA), 1.29 % (PSO), 0.841 % (SSA), and 0.03 % (GSO-PID), underscoring its substantial effectiveness. Practical implementation further validates the improved THD performance. The paper's findings highlight the efficiency and potential of the integrated DVR unit with a solar PV system in effectively mitigating power quality issues. These results offer valuable insights for researchers and practitioners seeking advanced solutions to power quality challenges. Future research endeavors aim to optimize and expand this approach for diverse power quality improvement applications. [ABSTRACT FROM AUTHOR]

• This study presents a novel method for protecting VSC-DC systems. It uses wavelet analysis of current waves collected from both ends of the transmission line to find faults in the DC system using detailed coefficients. • It utilizes such coefficients to train an adaptive fuzzy neural inference system to select whether the faults are in the direct current DC or the alternating current AC systems. • Finally, the proposer uses continuous training of the ANFIS to define fault location. • It achieved the concept of reliability by accurately locating the fault along the transmission line regardless of the effect of modifying the noise levels. • The research executed a practical validation under different faults. Protecting direct current transmission lines (DC-TLs) against faults is challenging and crucial, especially when locating faults. This research aims to develop a novel distance protection approach for Medium voltage direct current transmission lines (MVDC-TLs). Various faults in the computerized experiments and practical models have been applied to the proposed system in the AC network and DC transmission lines to evaluate the performance of the proposed method. The proposed protection system employs the wavelet transforms (WT) and ANFIS as detailed coefficients 'feature extracting' tools and classifiers, respectively. The mechanism operation of the proposed method is composed of three stages. Firstly, it extracts the features of the faults by WT. Hence, the ANFIS training process uses such features to identify and classify the faults. The third stage utilizes the ratio value between the fault current and the healthy operation current as an input of another ANFIS model to locate faults on the DC TL. The performance of the proposed protection method has been tested and evaluated for MVDC and MVAC networks. Also, the research executes both practical and simulation experiments utilizing different faults. It examines various fault locations on the entire MVDC line. The mechanism measures the current signals on both sides of the DC-TL. The paper built the MVDC-TLs model and the different cases using the software PSCAD/EMTDC and the proposed method via MATLAB. The study tested faults along the TL in the presence of the AWGN noise. The research utilizes practical experiments to verify the accuracy of the proposer. The accuracy of the proposed fault location is 99.923 %. Based on the results of this research paper and comparison with the recent related research works, the proposed method is more effective and efficient than the previous methods in detecting, classifying, and locating system faults. [ABSTRACT FROM AUTHOR]

• Local markets with eventual local electricity prices might be beneficial for community users. • Local electricity tariffs should be stable and send coherent response signals easily interpretable by users. • Necessity of developing proper designing tools for local electricity tariffs is clear. • The designer is able to tune up the total number of pricing signals. • A designed bi-level Stackelberg-based problem. In recent years, energy communities have emerged as a feasible solution to empower domestic end-users to engage in local power trading with their neighbours, in an attempt to improve the efficiency and economy of residential consumers. From a mercantilist point of view, launching local markets with eventual local electricity prices might be beneficial for community users as they are inhibited from external volatile prices and possible market imperfections. However, local pricing strategies should take into account users' preferences and avoid undesirable effects of response fatigue (i.e. excessive number of response signals within a short-time period). This way, local electricity tariffs should be stable and send coherent response signals easily interpretable by users. In this sense, the necessity of developing proper designing tools for local electricity tariffs is clear. This paper focuses on this issue. In particular, the main novelties of this paper are twofold: on the one hand, the developed tool designs community tariffs over a year basis instead of daily spot prices, as made in existing approaches. Thereby, the resulting tariff keeps stable yearly similar to conventional tariffs offered by retailers worldwide. Secondly, the designed tariff takes into account the negative effects of response fatigue, so that the considered pricing mechanism limits the number of pricing signals sent to consumers, taking this feature as an external parameter. This way, the designer is able to tune up the total number of pricing signals that users received within a time period, thus ensuring that they are not discouraged to partake in the community. The proposed design approach is raised as a data-driven framework, taking advantage of real databases collecting demand, renewable generation and retailer prices. Such profiles serve as inputs for a designed bi-level Stackelberg-based problem, in which the reaction of prosumers is implicitly assumed. A case study is conducted on a benchmark energy community. Different tariff mechanisms are analysed such as flat, time-of-use and happy hours tariffs. The results obtained serve to validate the new proposal as well as analyse the effect of local market mechanisms in energy communities. [ABSTRACT FROM AUTHOR]

• A new control method for DER is suggested. • The proposed control method balances the load between feeders. • DER connects to feeder through SST. • DER-controlled circuit shared the load between two feeders like ring connection. • Voltage profiles are improved. The multi-purpose use of distributed energy resources (DER) can bring a lot of income to its owners. For example, the load imbalance of the radial feeders in the distribution network is an old problem that occurs due to the simple structure of the radial topology and the unidirectional power flow in traditional networks. With emerging DERs and the development of power electronic technology, previous concepts are changing continuously. This paper aims to balance the load between two feeders whilst, it yields better voltage profiles and more appropriate utilization of distribution feeders. This paper proposes a new control method for DERs (including PV panels plus battery storage) that makes the radial system pretends a ring topology properties. It is done with the help of a solid-state transformer (SST). The relationships of the DER current controller are formulated based on current passes through the ring connection. Case studies are carried out on improved IEEE 33-node and 13-node systems with DERs and SSTs. The results show that the suggested control method can simulate the real ring topology and operating objective namely, load balancing is reached. [ABSTRACT FROM AUTHOR]

• Based on Lagrange duality theory and binary variable characteristics, ADMM's sub-problem is solved efficiently. • The unit status based on the solution set of ADMM is sorted, and the appropriate units are obtained for local search. • Solve UC problems with unit sizes above 1000 in the 1800 s, and the relative gap of the solution is less than 1 %. In the modern electricity market, solving the unit commitment (UC) problem becomes more challenging due to its large number of binary variables and coupling constraints. Therefore, the goal of this paper is to obtain nearly optimal solutions for such complex UC problems within specific time limits. To achieve this, a hybrid approach is presented in this paper, which incorporates a splitting technique and a local search for UC. The hybrid approach involves two steps. In the first step, the augmented Lagrange function (ALF) of UC is decomposed using a splitting technique based on the alternating direction method of multipliers (ADMM). The resulting sub-problems can be effectively solved in a distributed manner by utilizing Lagrange duality theory and binary variable characteristics. Additionally, the penalty parameters of the ALF are updated effectively with the sub-gradient method to diminish the influence of the initial penalty parameters on the algorithm. In the second step, the appropriate relaxation unit is selected using the binary variable characteristics in the current solution of ADMM. Further, the high-quality feasibility of the final solution is ensured through local search. The hybrid approach utilizes ADMM to quickly fix most binary variables in the UC model and then leverages the CPLEX solver to solve the mixed-integer linear programming (MILP) formulation of UC by fixing a large number of binary variables. Consequently, the CPLEX solver needs to branch fewer binary variables, reducing the local search time. The hybrid approach is applied to solve several power systems consisting of up to 1000 units. Compared with the CPLEX solver, the solution of the hybrid approach is found to be stable, and the relative gap of the solution is less than 1 %, demonstrating the effectiveness and performance of the proposed approach while meeting the time limit requirements of the power industry dispatching. [ABSTRACT FROM AUTHOR]

• This paper proposes a novel fast time-domain protection scheme in a large-scale PPP system, with prominent features such as simplicity. • There is no need of parameters tuning because of the adaptive nature of ITD. Also, all the protection scheme parameters are determined analytically, such as threshold value and number of iterations. • A wide variety of fault scenarios are analyzed for fault detection such as different fault resistance, location and types. • Communication medium is not required. Consequently, there is no communication delay and data loss. • The protection scheme's capability in various conditions such as noisy environments, uncertainty in renewable energy generation, change in GC, various sampling frequencies and CT saturation is discussed. • The proposed protection scheme is tested in two the 2-bus and IEEE 39-bus test systems in MATLAB and PSCAD environments. The performance of a distance relay can be significantly affected by various uncontrolled factors such as fault resistance, fault type, fault location and noise. Moreover, when photovoltaic power plants are integrated into electrical grids, they exhibit distinct fault current characteristics compared to conventional power systems with synchronous generators. These factors introduce variations in the recorded apparent impedance, deviating from the predefined settings of the distance relay. This paper presents an effective scheme for fault detection using ITD methodology. The ITD method decomposes the target signal into proper rotation and monotonic signals, which are then used to calculate the Energy Index. The performance of this scheme has been extensively investigated under various scenarios, including fault resistance, fault location, fault type, CT saturation, GC compliance, noise, and sampling frequency. To validate the effectiveness of the proposed scheme, simulations are conducted using both the PSCAD/EMTDC and MATLAB software. The proposed scheme is assessed using both the 2-bus and IEEE 39-bus test systems. The results show the merit and effectiveness of the proposed scheme in the accurate diagnosis of fault detection with 400 Ω fault resistance, in the presence of 20 dB noise, with variable sampling frequency (0.5-16 kHz) and variable irradiance values (600-1000 (W / m 2)) in power systems. [ABSTRACT FROM AUTHOR]

• Studying the insulator arc clearing effect upon OHTL systems. • Quantifying the effect of arc clearing by defining overvoltage's, and arc extinction time. • Discussing arc clearing impact on OHTL under Corona, arc distances, tower footing impedances, and inception angles. • Evaluate the performance of the overvoltage different mitigation methods. In high-voltage OHTL, Overvoltages and arc currents due to insulator transient arcs clearing severely affect the stability of power systems. In this paper, a 500 kV Egyptian OHTL was simulated using ATP-EMTP software package. The insulators transient arcs clearing of the system were tested under different impedances of tower footing, locations of insulator arc tower, angles at which the arc initiate. Additionally, the effects of the corona phenomenon were taken into account to achieve realistic study. Furthermore, these factors thoroughly were analyzed to determine worst-case scenarios. Also the paper evaluated the performance of the overvoltage mitigation methods based on the installation of neutral shunt reactors, MOSA (Metal Oxide Surge Arresters), or combinations of both. The results demonstrated that the combination of MOSA and neutral shunt reactors was the most effective mitigation technique, reducing overvoltages by approximately 57.4 %, arc currents by 80 %, and arc extinction time by 27.3 % Notably, the most severe overvoltages and peak arc currents occurred at an angle of θ = 180° and footing impedance 30Ω. Additionally, the corona phenomenon played a role in reducing the severity of overvoltages, arc currents, and arc extinction time by approximately 56 %, 56 %, and 1.8 %, respectively. Finally, These findings provide valuable recommendations for mitigating overvoltages, arc currents, and arc extinction time during insulator arc clearing events. [ABSTRACT FROM AUTHOR]

• The experiment observed, recorded and analyzed the natural icing process of insulators, but most of the previous studies were simulated in the laboratory. • This paper analyzed the icing process of different types of insulators (shed structure, Shed diameter) under natural icing environment. • The influence of wind speed, humidity, precipitation and temperature on the natural icing process were analyzed. • Based on the final icing morphology under natural condition, this paper took the of icicle number, icicle length, icicle diameter, icing thickness of shed surface and icing mass as characteristics, analyzed the differences in icing results of different structures insulators, and got the conclusion (4), which provides reference for insulator selection of transmission lines in icing areas. Icing flashover of insulator strings has always been a serious factor threatening the safety and stability of the power grid. Researchers have simulated icing based on an artificial climate chamber, but it cannot fully simulate the growth process of insulator strings during the icing period in the natural environment. The icing growth characteristics of insulator strings in the natural environment are not clear. In this paper, three kinds of porcelain insulators were tested in the Xuefeng Mountain natural icing test base of Chongqing University. The results show that the freezing rain, alternating icing of freezing rain and freezing fog can cause the insulator stings to form glaze and mixed rime, and the icing degree on the windward side is more serious than leeward side. The higher the test environment's precipitation, humidity and wind speed, the faster the insulator strings' icing speed. And there are also some influences of the ambient temperature on the icing morphology in this test. The icing thickness on the windward side of the insulator shed will gradually increase. The number of icicles of insulators is positively correlated with the diameter of insulator sheds. The icing mass of insulator strings is seriously affected by their shed structure. [ABSTRACT FROM AUTHOR]

• Detailed modeling of CIGRE-14 bus standard test system along with inverter control scheme (with and without grid code) and protection system is done in PSCAD environment. • The performance of directional relaying schemes (32Q and 67pos,67neg,67zero) are evaluated in the presence of inverter-interfaced renewable energy resources. A comparative study on the performance of the relays is done in the presence of inverter-interfaced renewable energy resources for different fault types and fault resistances. • The interdependencies between the inverter control scheme used and performance of relaying schemes have been analyzed through mathematical analysis and circuit realization of the inverter-interfaced renewable energy resources. • Based on the mathematical analysis and circuit realization, the probable causes of relay failures in the presence of inverter-interfaced renewable energy resources are detailed. • The impact analysis of the dynamic response of the controller on the protective relay settings from the perspective of protection operation time-frame has been attempted. The potential impacts of the inverter-interfaced renewable energy resources (IIRERs) on the performance of sequence-based directional relaying schemes (SBDRS) have been investigated in this paper. The directional overcurrent relays such as 67 POS , 67 NEG , 67 ZERO and 32Q have been considered for the investigation. CIGRE-14 bus system with IIRERs along with detailed modeling of inverter control scheme (with and without grid codes) and SBDRS have been done in the PSCAD environment. The mathematical analysis and circuit realization of the IIRERs have been attempted in the paper. The exclusive fault characteristics exhibited by IIRERs cause the conventional SBDRS to mal-operate. Significant change in levels of sequence currents and angular relationships between sequence voltages and currents during faults contributes to relay's unpredictable behavior. The comparative study based on different fault types, fault resistances and interconnecting transformer connections have also been done. The study reveals the impact of non-generalized angular differences between positive sequence voltage and current at the inverter terminal on performance of 67 POS. It is found that 67 NEG and 32Q mal-operated for all types of unbalanced faults while the 67 ZERO can be utilized for grounded fault with delta-star grounded connection of interconnecting transformer. [ABSTRACT FROM AUTHOR]

• The generator startup process is modeled as the Markov Decision Process. • The Q-learning is applied in the planning of generator startup after blackout. • A new restoration strategy is proposed for the generator startup process. • The Upper Confidence Bound is used to optimize the selection of action of agent. With the expansion of the power system and the impact of natural disasters, blackouts are almost inevitable. A scientific restoration plan can effectively shorten the economic and social losses caused by blackouts. As the first step of power system restoration, the generator start-up process impacts the success rate and time consumption. Considering the diversity of constraints in the generator start-up process and the complexity of the topology, this paper proposes a planning method for the generator start-up process based on reinforcement learning. Q-learning is a model-free reinforcement learning algorithm that can cope well with complex environments and diverse constraints. First, the generator start-up problem is modeled as a Markov Decision Process, and the restoration operation and constraints are considered. Q-learning uses an artificial intelligence agent to plan the generator start-up process and guide operators. Second, different from the restoration methods of sequential restarting the generators, this paper presents a novel strategy for restoration by restoring the path of the subsequent generator while the current generator acquires cranking power. Then, the action selection mechanism is optimized by using the Upper Confidence Bound algorithm to address the shortcoming of low exploration effectiveness in the conventional Q-learning. Finally, the simulation results provide evidence of the excellent performance of the proposed method in terms of optimality and convergence. [ABSTRACT FROM AUTHOR]

• Establish an optimization scheduling strategy for electrothermal joint operation. • Increase wind power consumption with electric boiler & heat storage tank. • Simulation shows 87 % wind power absorption rate with electric boiler & heat storage tank. • Combined use of electric boiler & heat storage lowers system operating costs. The intermittency and volatility of wind power and the characteristics of the operating mode of cogeneration units pose certain challenges to the wind power consumption of the power grid. To optimize the performance of the power and heat combined operation system and maximize the wind power consumption, this paper establishes a mathematical model for each component of the cogeneration system, including the thermal dynamic characteristics of the heat network, buildings, cogeneration units, electric boiler, and heat storage tank. At the same time, a scheduling optimization model is proposed, which considers the power load demand, and wind power output of the regional heating system. The research results provide insights and optimal dispatching strategies for ensuring the reliable operation of the power system and heating system and realizing the efficient utilization of wind power. This paper verifies the effectiveness and feasibility of optimizing the cogeneration system and provides a practical solution to the challenge of cogeneration economics. [ABSTRACT FROM AUTHOR]

• Blackouts bring major economic and societal repercussions. • Efficient black-start strategy is critical to address increasing risk of blackouts. • Variable speed hydro can provide a fast response and is used during black start. • Meet black start needs with renewables and cutting diesel use. • RES-BESS boosts power and fortifies an integrated renewable grid. A blackout refers to a total power outage that rapidly plunges the electrical power system into a severe crisis, posing significant challenges for subsequent restoration efforts. Blackouts can occur due to a range of factors, such as delays in clearing faults, generator malfunctions, equipment failures, and human errors. After a blackout occurs, all possible measures are taken to achieve the fastest power system restoration. To ensure preparedness for such emergencies, scheduled black start exercises are conducted using units capable of initiating power restoration from scratch, allowing authorities to assess their readiness in catastrophic scenarios. Numerous similar exercises have been conducted regularly generating to highlight the complexities of power system restoration of the grid with the black starts of hydro generating units. This has aided plant operators in improving restoration methods and finding additional remedial steps to enhance existing processes to achieve an effective black start exercise. This paper overviews the multiple mock black start exercises applied to hydroelectric generating units and discusses several blackouts worldwide. In addition, Tehri Hydro Power Plant is considered for the case study. Tehri HPP is linked to the 400 kV EHV grid, which was later upgraded to 765 kV transmission lines. Further, this paper observes and discusses various challenges encountered during mock black start exercises. Possible remedial actions are suggested to address these challenges. [Display omitted] [ABSTRACT FROM AUTHOR]

• This paper analyses and mitigates the problems inherent in adopting bilateral co-phase traction network on Indian Railways by analysing and addressing the practical issues of voltage unbalance and circulating power. • This paper simulates the actual running conditions of Indian Railways with mixed traffic consisting of passenger trains, freight trains and slow and fast express trains. • It is demonstrated by simulation that reverse power flow to the grid degrades VUF. Thus it is proposed to install energy storage device on rolling stock and at TSS to improve VUF. Further, using bilateral co-phase system also degrades VUF but simulations show that it is within acceptable limits. • The scheme for installing voltage phase shifter in Indian Railway scenario is discussed and cost analysis is given to prove it's feasibility. The primary aim of this paper is to analyse and mitigate the problems inherent in adopting bilateral co-phase traction network on Indian Railways. The reason for adopting bilateral co-phase traction network is to enhance regenerative braking energy (RBE) utilization in the railway traction network. There are two inherent problems in adopting bilateral co-phase traction configuration. First, it may lead to increase in the Voltage Unbalance factor (VUF) as single-phase loading by trains is effectively doubled across the same phases. Second, and more importantly, it may lead to flow of circulating power, under no load conditions, where power shall flow from leading voltage traction sub-station to lagging voltage traction sub-station. This may offset any advantage due to improved RBE utilization. This paper demonstrates through simulation, using realistic data from Indian Railways, that VUF stays within limits for bi-lateral traction configuration. It is important to mention that improved RBE utilization also plays a role in reducing VUF when there is no feedback of RBE to the grid. For the second problem, this paper takes inspiration from a control scheme existing in literature to adapt it to the proposed scenario. This scheme shows that it is possible to limit the power angle within 0.5˚ and thereby minimising circulating power. [Display omitted] [ABSTRACT FROM AUTHOR]

• Elaboration of the full and reduced order of state space model of cascaded brushless doubly fed induction generator. • Design of the full state feedback control of cascaded brushless doubly fed induction generator with rotor current estimator. • Design of the reduced state feedback control of cascaded brushless doubly fed induction generator designed. • Comparative study of full and reduced order state feedback control of cascaded brushless doubly fed induction generator using MW range model of cascaded brushless doubly fed induction generator. The cascaded brushless doubly-fed induction machine (CBDFIM) is the developed version of a classic slip-ring doubly-fed induction machine (DFIM). Deprived of the main DFIM disadvantage - the slip-ring connection, the cascaded brushless doubly-fed induction machine has better durability and lower maintenance costs. Structurally it is realized by the presence of control stator and main stator working with a common rotor shaft. However, this type of electrical machine is characterized by much higher control inertia and larger dq control axis coupling, in comparison to DFIM. This fact makes problematic obtainment good dynamic performance and stability of the controlled system for classic control schemes. In the paper presented cascaded brushless doubly-fed induction machine state-feedback control schemes, based on CBDFIM full and reduced state-space model. Proposed algorithms allow control of CBDFIM generated active and reactive power components in a grid-tied operation and offer great possibilities of obtaining the desired dynamics parameters and stability of the controlled system. The main paper goal is to prove that reduced order state feedback control can be equally effective than full state feedback control in terms of obtained closed loop system dynamics and reduces influence of the couplings between the controlled variables. [ABSTRACT FROM AUTHOR]

• Proposed a protection scheme can determine the fault type only by calculating the similarity of one-mode current. • Based on the principle of one-mode current similarity, offering a viable solution to address the challenges arising from weak-infeed, frequency offset, and phase uncertainty caused by the LVRT strategy of the new energy station. • Proposed a protection scheme has good adaptability when the wind farm operates independently, and can also adapt to different wind farm capacity and energy storage ratio, which has certain application prospects in practical engineering. With the gradual growth of the scale of energy storage devices for wind power generation, a large-scale grid-connected wind-storage combined system (WSCS) has been formed. When the external transmission line fails, its control strategy will lead to problems such as limited output short-circuit current amplitude, frequency deviation from power frequency, and uncertain phase angle, which makes the traditional pilot protection possible to malfunction and refuse to operate. In order to solve this problem, this paper first analyzes the fault current output characteristics of the WSCS during low voltage ride through (LVRT), and its impact on the traditional pilot protection scheme. Secondly, considering the difference of fault current amplitude and phase change at both sides of the transmission line, the similarity relationship of one-mode current is verified. Finally, a pilot protection scheme based on one-mode current similarity is proposed in this paper. The simulation results conducted using PSCAD/EMTDC demonstrate that the proposed scheme exhibits robust anti-interference capability, capable of withstanding significant transitional resistance and noise, while maintaining good selectivity and reliability. [ABSTRACT FROM AUTHOR]

• Establish a source-load dual-side uncertainty model and consider the correction of customer responsiveness under time-of-use price for the load side • Consider the SOC characteristics of the energy storage system and perform nodal equivalence • Establish the power flow calculation model of source grid load storage AC/DC system • Introduce penalty function to establish a multi-objective optimization model for probabilistic optimal power flow and improve the power flow distribution at time t The randomness and fluctuation of wind turbines and photovoltaics affect the optimal operation of the power system. This paper aims to mitigate wind and solar fluctuations by integrating energy storage systems (ESS). One crucial metric for assessing the performance of energy storage systems is state of charge (SOC). Therefore, this paper proposes a power flow optimization method based on SOC characteristics. Firstly, we consider the uncertainties on both the generation and load sides of the power system and establish a source load model. Subsequently, an analysis of the SOC characteristics of the ESS is conducted, and associated constraints are provided. Then, a power flow model for the AC-DC system with voltage source converter (VSC) is developed based on the source load storage configuration. The optimization model is formulated as a multi-objective problem, utilizing penalty functions to minimize the overall economic cost, system losses, and line voltage deviations. Finally, the proposed method is validated through simulation analysis using an enhanced IEEE 30-node system as a case study. The simulation results confirm the correctness and effectiveness of the presented approach. [ABSTRACT FROM AUTHOR]

• Establish an inertia response model based on DC power flow. • Introduce RGA to evaluate inertia response. • Present a spatial characteristics analysis of inertia response using RGA. This paper proposes a novel method to evaluate the spatial distribution characteristics of inertia response in power systems. Under the effect of grid topology and the inertia distribution of generators, the influence of power disturbance on frequency variations during inertia response has distinctive spatial characteristics. Compared with early studies, this paper focuses on spatial characteristics and presents a quantitative method to evaluate inertia response. This paper first builds an inertia response model that retains spatial distribution characteristics by adopting DC power flow. Then, it introduces the relative gain array (RGA) theory for calculating the relative gain array between the rate of change of frequency (RoCoF) and the active power disturbance during inertia response. Based on the magnitude and distribution of the relative gain array elements, the paper conducts a quantitative analysis of inertia response, thus presenting a description of the spatial characteristics of inertia response. Simulation results of the IEEE 39-bus system validate the effectiveness of the proposed method in evaluating the spatial characteristics of inertia response. [ABSTRACT FROM AUTHOR]

• This paper introduces an advanced H∞ frequency control method for MGs, addressing uncertainties in secondary frequency control resources. By integrating parametric cyber uncertainties, it effectively counteracts unknown cyber-attack impacts, ensuring stable dynamic performance during cyber-attacks without requiring additional isolation or detection methods, simplifying MG control. • This study assesses cyber threats, incorporating physical uncertainties and RES/load fluctuations. It models key cyber threats (FDI, DoS, controller hijacking) and designs robust controls treating cyber-attacks and RES/load fluctuations as bounded uncertainties and disturbances. • The proposed H∞ control surpasses classical H∞ , optimal PI, and traditional frequency control in enhancing MG security, control, and functionality. It enables proactive control across diverse scenarios, ensuring cyber robustness, resilience, and uninterrupted performance against potential disruptions. • The application of the proposed robust control can be extended to the interconnected MG operations, significantly improving overall robust performance, even when the robust control is implemented in just one area during multiple cyber-attack events. A microgrid (MG) is a smart grid cyber-physical system, with component coordination relying on cyber resilience. Weak communications, protocols, and tools make the MG's secondary frequency control vulnerable to various cyber-attacks, posing new challenges and stability risks. In response to this challenge, this paper introduces the enhanced robust H ∞ technique considering the dynamic impacts of cyber-attacks on secondary frequency control to develop a secondary frequency control loop, improving the regulation performance and cyber resiliency of the MG frequency. The secondary control cyber-attack strategies mainly rely on false data injection (FDI), denial of service (DoS), and controller hijacking. These attack techniques are simultaneously considered in formulating the H∞ problem and control synthesis as unstructured parametric uncertainty, attenuating the concurrent cyber impacts. The study extends a load frequency control model to illustrate how cyber-attacks can be represented mathematically and physically in the MG. The results reveal that cyber-attacks affect secondary frequency control elements differently depending on the type of cyber threats used. By implementing an enhanced H∞ controller, the MG can effectively maintain stable frequency levels even when faced with malicious attacks and disruptions caused by renewable energy sources and loads. [ABSTRACT FROM AUTHOR]

• A multi-objective model is proposed, which contains both the cost and carbon emission objectives. The sizing of the grid-connected converter is included. The carbon emission of the power from the grid is considered. The model can comprehensively describe the requirements of LVDC systems in the economy and environmental protection. • This paper considers the effect of EVs on the sizing of LVDC systems. Both the charging and discharging of EVs are fully used to reach better sizing and operation for the system. • A minimum fuzzy carbon emission method (MFCEM) is given to transform the multi-objective into a single objective. Compared with the linear weighting method, MFCEM is a useful method for finding a point on the Pareto front that balances cost and carbon emissions. Grid-connected low-voltage direct current (LVDC) systems offer a promising solution for achieving low-carbon buildings. However, a new challenge arises in sizing grid-connected LVDC systems, which is to fully utilize distributed renewable energy, energy storage, and load demand response to minimize both the economy and carbon emissions. To address this gap, this paper studies the sizing of grid-connected LVDC systems, considering the grid-connected converter, photovoltaic (PV), battery, and demand response of electric vehicles (EVs). Firstly, two objective functions are proposed, including the economy and carbon emissions. Secondly, constraints for sizing and operation are presented, with particular consideration given to the discharging of EVs and the corresponding cost of cycle-life loss. Finally, a minimum fuzzy carbon emission method (MFCEM) is proposed to solve the model, which can adaptively and objectively transform the multi-objective into a single objective. According to the case study, the proposed model comprehensively considers the cost and carbon emissions of grid-connected LVDC systems, and its feasibility and validity are verified. Compared with the linear weighting method, MFCEM is a useful method for finding a point on the Pareto front that balances cost and carbon emissions. [ABSTRACT FROM AUTHOR]