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When the T-connected transmission line fails, there is a certain relationship between the phases of the three-terminal power frequency fault current, which can be applied to protect the current differential of the T-connected line. In this paper, using the MATLAB/Simulink electric power system simulation software, when the T-connected transmission line is faulty, the power frequency fault current variation law monitored at the installation point is deeply studied, and the judgment method of the T-connected transmission line fault branch based on the power frequency current is proposed. [ABSTRACT FROM AUTHOR]

The transience and unpredictability of processes in electric power systems (EPS) determine complexity of its control. This problem is especially relevant for EPS with renewable energy sources and flexible alternating current transmission systems technologies. Automatic control systems simplify the solution of this problem. Despite this, many issues related to EPS state control are solved by power system operators. Decision support systems (DSS) are applying to increase efficiency of operators work. However, existing algorithms in practice are inoperable in some cases: unrealizable decisions are formed, or decision cannot be found at all, etc. Another important problem is impossibility to preliminarily verify the proposed solution. In this regard, operators can additionally use EPS simulators, which are usually limited either by the size of simulated scheme or by the details of equipment mathematical models. The limitations are a consequence of numerical methods using, which are badly applicable for large-scale power systems simulation. In this article, a novel DSS has been developed based on a hybrid approach to EPS modeling combining properties and capabilities of several simulation techniques: analog, physical and digital. The implicit integration of differential equations in analog way makes possible modeling faster than real time. Such opportunity allows operator to verify more decisions and select the most effective ones. The algorithm for DSS application has been developed and described in the article. The properties and capabilities of the developed DSS are confirmed by experimental studies and tests in a real EPS. [ABSTRACT FROM AUTHOR]

Time of use pricing strategy can not only reduce the load fluctuation but also improve the power system reliability. Generally, before carrying out a time of use pricing optimization, it needs to perform a period partition optimization for dividing peak‐valley periods. In existing researches, however, the period partition optimization and the time of use pricing optimization are implemented independently. Although the output of period partition optimization is used as the input of time of use pricing optimization, the bidirectional feedback effect between period partition optimization and time of use pricing optimization is not considered, which will lead to the existing time of use pricing optimization may not be the globally optimal solution. Therefore, this paper investigates a new optimization method for time of use pricing optimization with the consideration of bidirectional feedback effect, establishes a comprehensive customer satisfaction degree model considering the customer load proportion coefficient, and defines an elastic cofactor to describe the electricity price response difference of multiple types of customers. The Roy Billinton test system is used to verify the correctness and effectiveness of the proposed method in this paper. [ABSTRACT FROM AUTHOR]

As the penetration level of converter-based generators (CBGs) continues to grow in electric power systems, their impact on power system dynamics and control becomes increasingly significant. Maintaining a stable operation of the CBGs is becoming more and more critical. Since their controls and dynamic behaviour differ from synchronous generators, in this study, the transient stability mechanism of CBGs is analysed and the key influencing factors are identified and investigated. Moreover, a stability margin index, which can be obtained analytically, is proposed to identify potential transient stability issues of CBGs and can be used as a screening technique before conducting time-consuming electromagnetic simulation studies. This index can be used for both planning and operations studies and it outperforms the state-of-the-art index of short circuit ratio that is presently used to identify potential CBG instabilities due to weak grid scenarios. Dynamic simulations on a real power system model have been conducted to validate the accuracy and applicability of the proposed stability margin index. [ABSTRACT FROM AUTHOR]

Currently, an issue of relay protection (RP) settings determination that ensures its correct operation in electric power systems (EPSs) has not been resolved completely. The main reason for this is the lack of methods and tools for adequate consideration of transients during a fault existence for RP settings calculation. In this study, a novel approach for RP settings determination is presented. Its main feature is the application of detailed mathematical models reproducing simultaneously processes in the entire set of elements in the RP scheme, including instrumental transformers, and in large‐scale EPS mathematical model as a whole. This key feature can be achieved via the hybrid power system simulator – hybrid real‐time power system simulator – implementing a methodically accurate analogue–digital solution of the EPS mathematical model. The numerical transformer differential protection (NTDP) based on this approach was set up via the standard dual‐slope tripping characteristic. Also, a novel approach to the formation of the tripping characteristic is proposed. The key feature of this approach is applying a flexible curve that enveloping all fault characteristics Idiff = f (Irest) of those modes in which the NTDP should not trip. [ABSTRACT FROM AUTHOR]

Currently, the number of distributed generation (DG) objects in the world is growing mainly due to renewable energy sources (RES). However, the integration of a large volume of DG based on RES into existing electric power systems (EPS) is associated with a number of significant problems. For a comprehensive study and solution of these problems, it is necessary to carry out detailed simulation of real EPS, which is not always feasible with the help of existing tools. Therefore, the article proposes the use of an alternative solution – the Hybrid Real-Time Power System Simulator (HRTSim). To confirm the properties and capabilities of the HRTSim, the simulation results of a test scheme obtained using the HRTSim and the widely used digital hardware-software complex RTDS were compared. The results of a comprehensive comparison in both complexes confirmed the adequacy of information about the processes in equipment and EPS as a whole, obtained by the HRTSim. Thus, it is proved that further use the HRTSim as a tool for detailed and adequate simulation of real EPS with DG will provide complete and reliable information about normal and abnormal quasi-steady-state and transient processes, which is necessary for reliable and efficient design, research and subsequent operation of EPS with DG. [ABSTRACT FROM AUTHOR]

The reliability and efficiency of electric power system (EPS) operation depends on the adequacy of the information about processes in the EPS. The complexity of obtaining this information lies in the need to use large-scale EPS mathematical model for calculations. Within the framework of numerical integration, a satisfactory solution of such model is hardly to be ensured; consequently, the simplifications and limitations are applied. In this regard, every obtained solution should be validated. The most reliable way of validation is to compare simulation results with field data. However, it is not always possible to receive the necessary amount of field data. The paper proposes an alternative approach for validation: the adequate reference model (RM) usage instead of field data. The prototype of hybrid real-time power system simulator having the necessary properties and capabilities is used as the RM in this paper. The adequacy of proposed approach is illustrated by the fragments of the experimental studies. [ABSTRACT FROM AUTHOR]

In this paper, a new synchronous machine model is developed for electromagnetic transients program type simulations. The stator circuit is expressed in the abc phase domain. The machine model is represented as a Norton equivalent with a current source in parallel with a constant Norton admittance. The machine equations are reformulated so that the computational effort required for the modeling of the machine is reduced. Test studies demonstrate the accuracy of the proposed synchronous machine model and show that the proposed model is computationally more efficient than the existing constant conductance phase domain model and voltage-behind-reactance model. [ABSTRACT FROM AUTHOR]

Large-scale integration of wind generation changes the power swing characteristics of a power system and may result in the misoperation of legacy power swing protection schemes. This paper presents a qualitative study on the impact of wind generation on power swing protection. The objective is to provide an understanding of the problem through case studies and present possible solutions and adjustments in protection schemes to ensure the efficiency of protection under large-scale integration of wind generation. The misoperation of power swing protection functions, namely power swing blocking and out-of-step tripping (OST), as a result of increased wind generation levels, are shown through case studies. It is also shown that the electrical center of a power system may move due to wind generation. In this case, it would be necessary to revise the optimal location of the OST protection. Finally, the impact of various factors, such as wind generator type, control scheme and fault-ride-through function, and wind generation level and capacity are investigated to determine the key features that need to be accounted for in practical protection studies. [ABSTRACT FROM AUTHOR]

Highlights • A general framework for model validation from frequency perspective is proposed. • New parameters, Frequency Ramp Rate (FRR) and Activity Range (AR), are introduced. • A quantitative assessment method is proposed for the model validation process. • Proposed framework is implemented successfully for a large and real power grid. • The steps of implementation are clarified through detailed results and discussion. Abstract This paper proposes a quantitative model validation framework from the frequency perspective in which some of the technical issues of the process are solved. Two influential parameters of the process, namely the frequency ramp rate and activity range are introduced. A new quantitative assessment method including indices development and threshold calculation method is proposed. In order to reduce the complexities and efforts, all the capabilities of the existing models are initially tried (as approach 1) and upon its failure, more complex models are developed and employed (as approach 2). After discussing the theoretical aspects, the implementation steps and effectiveness of the process are demonstrated by applying the framework to a large and real power system. Some solutions for the practical issues are proposed and implemented. Since the simulation results of the first approach exceed some specified thresholds, the second approach is followed. Quantitative assessment of the second approach proves that the simulation results satisfy the specified thresholds for all incidents. The prominent and vital effect of different influential parameters and improving actions of the process are also demonstrated on the validated model. [ABSTRACT FROM AUTHOR]

The trend in semiconductor developments has made the high-voltage direct current (HVDC) technologies based on voltage source converters feasible. This type of convertor has a number of potential advantages compared with "classic" HVDC, but deep analysis should be carried out before its integration in electric power system. In this paper, the results of realization of the VSC HVDC model based on a concept of hybrid simulation of electric power system are presented. Hybrid concept combines three approaches of simulation: analog, digital and physical, combination of which allows to achieve a maximum efficiency. The obtained simulation results have confirmed an adequacy of the model and possibility to integrate it to the hybrid real-time simulator for carrying out various researches and analyses of the operation of large electric power system, including HVDC technologies, in real time without any decompositions and limitations. [ABSTRACT FROM AUTHOR]

This paper develops a comprehensive dynamic-phasor-based small-signal model for the modular multilevel converter (MMC) system under unbalanced grid conditions, which takes into consideration the dynamics of the MMC system under a balanced grid condition as well as the other emerging internal harmonics produced by the unbalanced grid components and more complex controllers. The small-signal model is validated by comparing the time-domain responses from a detailed electromagnetic transient (EMT) simulation in PSCAD/EMTDC. Based on the eigen-analysis and PSCAD-based time-domain simulation studies, this paper reveals the poorly damped modes that cause unstable oscillations in MMC system under the unbalanced grid conditions. From the results, more poorly damped modes involved in the internal harmonics are emerging under unbalanced grid conditions compared with the modes under the balanced grid conditions, and can highly impact the system dynamic behaviors by the selection of the control parameters. It is also shown that, under the unbalanced grid conditions, the feasible region of the control parameters of the vector current control gets narrowed indicating the reduction of the stability margin, smaller (larger) value of proportional (integral) gain of the circulating current suppressing controller can enhance the system stability, and larger values of the proportional and integral gains of the negative-sequence current suppressing control can result in the harmonic instability of the MMC system. Besides, the parameters of multiple complex-coefficient filters for positive- and negative-sequence components extraction also have a big impact on the small-signal stability of the MMC system and are required to be properly selected. [ABSTRACT FROM AUTHOR]

Highlights • Identifying events from PMU data is a difficult recognition exercise. • Time series may be transformed into 2D images. • Convolutional neural networks can accurately recognize images and identify events. • A GPU accelerates training down to seconds, compatible with operation environment. • 100% positive recognition achieved for 4 types of events in the Brazilian system. Abstract This paper presents a new method to identify classes of events, by processing phasor measurement units (PMU) frequency data through deep neural networks. Deep tapered Multi-layer Perceptrons of the half-autoencoder type, Deep Belief Networks and Convolutional Neural Networks (CNN) are compared, using real data from Brazil. A sound success is obtained by a transformation of time-domain signals, from dynamic events recorded, into 2D images; these images wee processed with a CNN, taking advantage of the strong dependency existing among neighboring pixels in images. The training, computing and processing was achieved with a GPU (Graphics Processing Unit), allowing speeding-up of the process up to 30 times and rendering the process suitable to increase the online situational awareness of network operators. [ABSTRACT FROM AUTHOR]

Composite power system reliability evaluation is computationally time-consuming because the optimal power flow (OPF) with the least load curtailment is calculated for a large number of samples. Most current studies of probabilistic simulation methods focus on sampling techniques to improve the sampling efficiency and decrease the calculations of the OPF. This paper proposes a fast reliability evaluation method that accelerates the calculation of the OPF using multi-parametric linear programming (MPLP). In this paper, the sampled transmission line statuses are considered by the transmission line status dictionary (TLSD). We match the line status of each sample with the scenarios in the TLSD. For matching samples, the generation status and the sampled load are treated as MPLP parameters of the DC-OPF evaluation model. A dynamic learning algorithm is applied to solve the MPLP problem. Case studies are conducted on both IEEE Reliability Test Systems and a provincial power system in China. The results show that the proposed method improves the evaluation efficiency by 23–30 times compared with the normal DC-OPF-based model. [ABSTRACT FROM AUTHOR]

This work considers the task of finding an ac-feasible operating point of a severely damaged transmission network while ensuring that a maximal amount of active power loads can be delivered. This AC maximal load delivery (AC-MLD) task is a nonconvex nonlinear optimization problem that is incredibly challenging to solve on large-scale transmission system data sets. This work demonstrates that convex relaxations of the AC-MLD problem provide a reliable and scalable method for finding high-quality bounds on the amount of active power that can be delivered in the AC-MLD problem. To demonstrate their effectiveness, the solution methods proposed in this work are rigorously evaluated on 1000 $N$ - $k$ scenarios on seven power networks ranging in size from 70 to 6000 buses. The most effective relaxation of the AC-MLD problem converges in less than 20 seconds on commodity computing hardware for all 7000 of the scenarios considered. [ABSTRACT FROM AUTHOR]

Measurements from the on-board systems of marine vessels are increasingly available for data analysis and are growing in importance as the ship industry enters a phase of digitalization. The purposes of the data analysis from vessels in operation include the verification of the power system design in general and improvement of the electrical power load analysis in particular. In this paper, we show how to extract valuable information from the data-driven operational profile analysis, which reveals the real power demand, and how the vessel was operated. Using the real power range analysis, we emphasize the significance of rarely occurring high power demands, which are critical for power system design and optimization. We propose a methodology for the quantification of variability in the generated power, which explains the tails of probability distributions of a power signal based on signal decomposition. The proposed methodology makes use of the data and it can facilitate the selection of the optimal size, number, and configuration of generators or batteries when designing new power systems. Measurements from a data collection system are used to demonstrate the methodology for dynamic positioning mode of the operation of a platform supply vessel. [ABSTRACT FROM AUTHOR]

A continuous Online Monitoring System (OMS) for power system stability based on Phasor Measurements (PMU measurements) at all the generator buses is proposed in this paper. Unlike the state-of-the-art methods, the proposed OMS does not require information about fault clearance. This paper proposes a convolutional neural network, whose input is the heatmap representation of the measurements, for instability prediction. Through extensive simulations on standard IEEE 118-bus and IEEE 145-bus systems, the effectiveness of the proposed OMS is demonstrated under varying loading conditions, fault scenarios, topology changes, and generator parameter variations. Two different methods are also proposed to identify the set of critical generators that are most impacted in the unstable cases. [ABSTRACT FROM AUTHOR]

Time-domain simulation is the basis of dynamic security assessment for power systems. Traditionally, numerical integration methods are adopted by simulation software to solve nonlinear power system dynamics for any given contingency under a specific operating condition. An alternative simulation approach promising for online applications is to offline derive a semi-analytical solution (SAS) for power system differential equations and then online evaluate the SAS over consecutive time windows regarding the operating condition and contingency until the simulation result over a desired period is obtained. This paper proposes a general semi-analytical approach that derives and evaluates an SAS in the form of a power series in time to approximate the true solution. This paper provides an error-rate upper bound of the SAS for reliable use of adaptive time windows in evaluation of the SAS. To extend the semi-analytical approach for solving general power system differential-algebraic equations, this paper also proposes a dynamic bus method to efficiently link the SAS for dynamic components with the numerical solution of the network algebraic equations. Case studies on the New England 39-bus system and the Polish 2383-bus system test the performance of the proposed approach, compare it with other methods, and show the potentials of the proposed semi-analytical approach for online simulation. [ABSTRACT FROM AUTHOR]

In previous research, the variable conductance of a parallel active power filter has been used for antiparallel resonance with parameter variations in power systems. Its disadvantages are many sensors, complicated harmonic detection, and complexity of the algorithm for successful accomplishment in antiparallel resonance. In order to eliminate such drawbacks, this paper presents the parallel active power filter based on source current detection for antiparallel resonance with robustness to parameter variations for power factor correction using capacitor banks. The proposed method employs only single harmonic detector and an open-loop shaping design for robustness to variations of source impedance and a sudden change of capacitor bank values for power factor correction. The proposed antiparallel resonance controller can be readily applied to both large-scale and laboratory-scale power systems without any change. The large-scale simulation and the laboratory-scale experiment results confirm the validity, the accuracy, and good performance for antiparallel resonance, harmonic suppression, and robustness to parameter variations in power systems. [ABSTRACT FROM AUTHOR]

During recent years power systems are operated near the nominal capacity of system equipment with low stability margin. Operation of power systems in this condition is extremely risky and power systems lose their stability with any intense failure of system equipment. In bulk power system, it is more critical and may cause a partial or overall blackout. The capability of black start to bring back system to a normal condition in the case of partial or overall shut down is very important in each power system. When a shutdown occurs, power plants with black start capability supply cranking power for non-black start power plants, pick up critical loads and energize required transmission lines. These actions should be done in minimum time interval to maximize system provided energy during the restoration process. Most important decision making during restoration process is the determination of start-up sequence of generation units. During the restoration process, units with black start capability (BS units) start at the beginning of the process to provide cranking power for non-black start units (NBS units). Hence the determination of NBS units is decision variable in the restoration problem. In this paper, this problem has been described as a bi-level optimization problem which in upper level determines the optimal start-up sequence of NBS units by using a Teaching-Learning Based Optimization algorithm and in lower level determines the optimal transmission path with minimum number of switching and maximum reliability between any two necessary buses using the searching path graph-based algorithm. The proposed approach has been implemented successfully on IEEE 24-bus RTS and IEEE 118-bus test systems. [ABSTRACT FROM AUTHOR]

Wind storms such as hurricanes increase the outage rate of overhead transmission lines and hence can seriously affect the security of power systems. Therefore, it is very important to estimate the overhead transmission line outage rate for a power system that might be jeopardized by wind storms. In this paper, we propose a new method for estimating the outage rate of overhead transmission lines, with two primary advantages. First, the proposed method describes the relationship between the outage rate and the weather factors by a fragility curve customized for overhead transmission lines to ensure that the relationship is precisely represented. Second, the proposed method takes the conductor strength reduction and different physical properties of overhead transmission lines into consideration to increase outage rate estimation accuracy. We test the proposed method by estimating the outage rate of overhead transmission lines in a regional power system based on both historical and simulated wind storms. The test results show that the proposed method generates a more accurate estimation than the conventional approaches. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper describes the use of large electric grids in university electric power system courses. Since much actual power system information is not publicly available, the application of public domain synthetic grids developed by the authors is presented including a 2000-bus grid. Discussion of the educational applications utilized in a senior level class are given for power flow analysis and sensitivity, economic dispatch, contingency analysis, optimal power flow (OPF), security-constrained OPF, transient stability, and real-time dynamic operations. In each of these, the application of the large synthetic grids give students insights and experience with cases closer to actual power systems in complexity and size. [ABSTRACT FROM AUTHOR]

This study examines a modal condition to cause inter-area, low-frequency, electromechanical power oscillations in an interconnected power system with two subsystems. The modal condition being examined is the closeness of two electromechanical oscillation modes from each subsystem on the complex plane, which is referred to as open-loop modal resonance. The analysis in this study indicates that under the condition of open-loop modal resonance, the electromechanical oscillation modes of the interconnected power system are located at approximately opposite positions on the complex plane with respect to the resonant electromechanical oscillation modes of the subsystems. Hence, when open-loop modal resonance occurs, one electromechanical oscillation mode of the interconnected power system must have reduced damping. In this study, the damping reduction in the inter-area, low-frequency power oscillations caused by open-loop modal resonance is demonstrated using example power systems. An incident of inter-area, low-frequency electromechanical power oscillations that occurred in an actual large-scale power system in China is examined. The examination results indicate that the poorly damped, inter-area, low-frequency power oscillation incident was caused by open-loop modal resonance. [ABSTRACT FROM AUTHOR]

The paper proposes a new adaptive approach to power system model reduction for fast and accurate time-domain simulation. This new approach is a compromise between linear model reduction for faster simulation and nonlinear model reduction for better accuracy. During the simulation period, the approach adaptively switches among detailed and linearly or nonlinearly reduced models based on variations of the system state: it employs unreduced models for the fault-on period, uses weighted column norms of the admittance matrix to decide which functions to be linearized in power system differential-algebraic equations for large changes of the state, and adopts a linearly reduced model for small changes of the state. Two versions of the adaptive model reduction approach are introduced. The first version uses traditional power system partitioning where the model reduction is applied to a defined large external area in a power system and the other area defined as the study area keeps full detailed models. The second version applies the adaptive model reduction to the whole system. The paper also conducts comprehensive case studies comparing simulation results using the proposed adaptively reduced models with the linearly reduced model and coherency-based reduced model on the Northeast Power Coordinating Council 140-bus 48-machine system. [ABSTRACT FROM AUTHOR]

The system frequency response (SFR) model describes the average network frequency response after a disturbance and has been applied to a wide variety of dynamic studies. However, the traditional literature does not provide a generic, analytical method for obtaining the SFR model parameters when the system contains multiple generators; instead, a numerical simulation-based approach or the operators’ experience is the common practice to obtain an aggregated model. In this paper, an analytical method is proposed for aggregating the multi-machine SFR model into a single-machine model. The verification study indicates that the proposed aggregated SFR model can accurately represent the multi-machine SFR model. Furthermore, the detailed system simulation illustrates that the SFR model can also accurately represent the average frequency response of large systems for power system dynamic studies. Finally, three applications of the proposed method are explored, with system frequency control, frequency stability, and dynamic model reduction. The results show the method is promising with broad potential applications. [ABSTRACT FROM AUTHOR]

Interarea power oscillation damping enhancement in large interconnected power systems is often accomplished using supplementary controls at the synchronous machines involved and with the use of flexible ac transmission system devices. The power system literature has demonstrated that wide area signals could be more effective than the local signals for these controllers. In some cases where phasor measurement units are used, all the required control signals may not be available. To alleviate these cases, control signals are obtained using estimated signals from a “dynamic state estimator,” and a robust supplementary controller is deployed. In this paper, the cited strategy is illustrated using a static var compensator. The feasibility of the proposed method has been demonstrated on the IEEE 50-generator test system. [ABSTRACT FROM AUTHOR]

Highlights • A new formulation for multi-objective unit commitment with voltage stability and PV uncertainty is given. • The proposed method can reduce operating cost as compared with conventional methods. • This method can be an appropriate tool for planning with the stability and PV uncertainty. Abstract This paper proposes a novel multipurpose operation planning method for minimizing the prediction error of photovoltaic power generator outputs (PV); towards reducing the operating cost and improving voltage stability of power systems. The operation schedule (coordination) of demand response (DR) program and storage system are taken into account as the main parameters for achieving an improved voltage stability and reduction of PV output prediction error. In this approach, the stochastic programming algorithm is introduced for incorporating the uncertainty of PV output and the utility demand response for consumer side management. This is achieved by using the multi-objective genetic algorithm (MOGA) for multipurpose operation plan. The MATLAB optimization toolbox and neural network toolbox were applied in this research study. An IEEE-6 bus system is used to demonstrate the effectiveness of the proposed solution in power systems operation. The approach led to $ 25003.39 (= $ 99594.53 - $ 74591.14) reduction in the system operating cost, compared to the conventional approach. The simulation results also show that by using the proposed algorithm, the capacity of installed PV generators was increased and the voltage stability was improved at the same time. This accounted for the reduction in the effective operating cost and the improved operating condition of the power system. [ABSTRACT FROM AUTHOR]

This paper develops a generalized framework that allows us to investigate the vulnerability of the power system nonlinear state estimator to false data injection attacks (FDIAs) from the operator's perspective and to initiate some countermeasures. Unlike most existing FDIA methods, which assume a perfect knowledge of the system measurements and topology by a hacker, we derive and analyze the uncertainties for launching successful FDIAs along with their upper bounds. To effectively defend against an FDIA, we propose a robust detector that checks the measurement statistical consistency using a subset of secure PMU measurements. We first show that if these secure PMU measurements are free of bad data while making the system observable, the FDIA is detectable. We then show that detectability is also ensured if these conditions are relaxed while using alternative redundant measurements from short-term nodal synchrophasor predictions together with the robust Huber M-estimator. Numerical simulation results on the IEEE 30-bus and 118-bus systems demonstrate the effectiveness and robustness of the proposed method even the secure measurements contain noise and bad data. [ABSTRACT FROM AUTHOR]

The usage of energy storage units in power system will reduce frequency oscillations immediately subjected to random load changes. In this project, investigations are carried out for an isolated power system with ALFC unit and isolated power system with mutual coupling effects. In each case the effect of different storage units is studied for random load changes. Here particle swarm optimization algorithm (PSO) and improved particle swarm optimization technique (IPSO) are used to tune the parameters of storage units to provide proper control strategy for the system. Instead of using two flexible storage devices, here one flexible storage unit is considered with constant storage system. Results are carried out in MATLAB/SIMULINK software. [ABSTRACT FROM AUTHOR]

In this paper, a new method called sine cosine algorithm is adapted in coordination with an interactive process to improve the power system security considering loading margin stability and faults at specified important branches. In this study, the loading margin stability is optimized in coordination with total cost, total power loss, total voltage deviation and voltage stability index. In order to locate the best loading margin stability, an initial global database containing suboptimized control variables is generated based on two indices named global and local critical reactive margin security related to generating units. The optimized loading margin stability is improved in coordination with the availability of reactive power of different shunt FACTS devices installed at particular locations. The robustness of the proposed planning strategy is validated on a small test system, the IEEE 30-Bus and to a large test system, the IEEE 118-Bus. Optimized results found confirmed clearly the improvement of loading margin stability at critical situations such as faults at specified branches. [ABSTRACT FROM AUTHOR]

Power system simulation is an important means to study the dynamic behavior, to ensure the safety and stability, and to optimize the operation of a power grid. Pure physical simulation and digital simulation have their own advantages and disadvantages. A three-phase four-wire hybrid simulation platform integrating the advantages of both the digital simulation and physical simulation is developed by combining the physical simulation system and real-time digital simulator. The platform is rated at 400 V and 50 kVA with the short-circuit capacity of 500 kVA and can supply ten times the rated current to support the simulation of various short-circuit faults. An improved interface algorithm based on an ideal transformer model is proposed to extend the stability region of a hybrid simulation. Hybrid simulation experiments are conducted under two cases, and the comparison with the digital simulation demonstrates the performance of this platform and the potential applied to a modern power system. This platform has been equipped in a key laboratory of smart power grid technology. [ABSTRACT FROM PUBLISHER]

Recently, Andreotti et al. (2015) have presented a new tool for lightning induced voltage calculations on power networks. This tool, named Circuit for Lightning Induced Voltage (CiLIV), has been initially developed for straight and vertical lightning channels; afterwards, the tool has been extended to evaluate induced voltages produced by tortuous lightning channels. However, in the aforementioned studies, only simple power network configurations have been examined. Therefore, aim of this paper is twofold: 1) to apply CiLIV to more complex network configurations, that is, complex networks equipped with transformers, surge arresters, groundings, and so on; 2) to investigate the effects of channel tortuosity on the voltages induced in these complex networks. [ABSTRACT FROM PUBLISHER]

SUMMARY In a distribution line, power system control and power equipment investment are planned based on a measured power system current. However, recently the mass introduction of photovoltaic (PV) make it difficult for us to precisely measure the demand curve that is a current consumed by electrical equipment because the reversal power flow from PV systems is superposed. Therefore, the prediction of demand curves of distribution line is indispensable for power system management. In addition, it is also necessary to estimate the reliability of the predicted values as well as predicted current itself. In this paper, we propose the estimation method of the prediction interval that is the index of reliability based on the past demand curve database. The feature of the proposed method based on Just-In-Time (JIT) modeling make it possible for us to accurately estimate the prediction interval by the normalized database of demand curve. In this paper, some numerical examples are presented, which demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Nowadays, the simulation tools used to perform power system analysis are evolving into the many-core computation era; some of these techniques propose to tear the power system network into several subnetworks (islands) for its parallel processing. The island's detection is an issue considered by the power flow analysis due to management activities such as feeder reconfiguration, fault detection, and isolation, among others, that generate topological changes. These methods include graph theory, checking the circuit breaker status and on-site measurements, decision trees, frequency deviation, and pattern recognition, among other techniques, which are focused to detect topology changes that may generate islands and affect the state estimation of the system. In contrast, other techniques such as the approximate minimum degree perform a reorganization of the $Y_{{\text{BUS}}}$ matrix that describes the network components and their connectivity, looking to factorizing the $Y_{{\text{Bus}}}$ matrix to solve the power flow problem. These techniques are very functional and efficient; however, some of them require detailed information of the network, and are addressed to cover meshed and radial network configurations separately. This paper presents an iterative algorithm that uses the compressed coordinate branch-to-node matrix for detecting, classifying, and grouping islands within sparse matrixes, describing mesh or radial networks. This algorithm is a valuable tool to simplify islands location and can be implemented using any programing language due to its simplicity. This method is used in Distribution System Simulator - Real Time Version (DSSim-RT), which is a simulator based in OpenDSS, for tearing the power system network to allow the multithread power flow analysis of distribution systems in real time. [ABSTRACT FROM PUBLISHER]

Global complete chaos synchronization in impulsive power systems with delay is studied. The sufficient conditions of exponential synchronization are established based on the theory of stability of impulsive differential equations with delay. Illustrative examples that demonstrate the applicability and effectiveness of the obtained results are given. [ABSTRACT FROM AUTHOR]

Many power systems applications such as power flow and short-circuit analysis require very large sparse matrix computations. With the increase in reliance on our electric infrastructure, power systems are continually growing in size, creating greater computational complexity in solving these large linear systems within reasonable time. For sparse matrix applications, it is desirable to have an algorithm with low runtime complexity in terms of the number of nonzeros in the matrix. There have been several recent advances in computational methods in other fields that, if applied to power system, could make real-time dynamic simulation a reality. Much work has been done for specific types of these problems where the system is symmetric and diagonally dominant, similar to the form of power system matrices. This paper details an expansion on the current work in fast linear solvers to develop power system specific methods that show potential for accurate solutions in $O(m \log ^2 n)$ run times, where $n$ represents the number of nodes and $m$ represents the number of nonzeros in the power system matrix. This paper presents the simulation validation of a recently developed recursively solved iterative chain method for sparse matrices using a low stretch spanning tree preconditioner. [ABSTRACT FROM PUBLISHER]

For a reliable and stable operation of a power system network, it is important to monitor the dynamics of the system. For this purpose, in real system phasor measurement units (PMUs) have been installed to give information about the grid conditions. Due to a large interconnected non-linear system, there is a possibility of system collapse due to unusual high stress. Hence, it is essential to detect the generators going out of step at an early stage and separate them. This study presents two algorithms: first one in meant to identify the coherency between the generators in real-time signal and second algorithm functions to quickly determine the critical generators. The algorithm for coherency identification between the generators uses time--frequency coherency based on smoothed pseudo-Wigner--Ville distribution signal processing technique. The proposed scheme is validated on several PMUs signals. Further, the Lagrangian method is applied to detect the critical sets of generators going out of step following the severe fault occurrence in the line. This is based on the calculation of energy. The suggested approach discussed in this study can be applied to dynamically reduce a large power system. [ABSTRACT FROM AUTHOR]

The framework for virtual integration of laboratories enables co-simulation and joint experiments that include hardware and software resources hosted at geographically distributed laboratories. The underlying concept of such framework is geographically distributed real-time (RT) co-simulation. To this end, digital RT simulators are interfaced over long distances via shared communication network such as the Internet. This study proposes an architecture for a modular framework supporting virtual integration of laboratories that enable flexible integration of digital RT simulators across Europe. In addition, the framework includes an interface that enables access for third parties via a web browser. A co-simulation interface algorithm adopted in this study is based on representation of interface quantities in form of dynamic phasors. Time delay between RT digital simulators is compensated by means of phase shift that enables simulation fidelity for slow transients. The proposed architecture is realised for the integration of laboratories across Europe that are located at RWTH Aachen University in Germany, Politecnico di Torino in Italy and at European Commission Joint Research Centres in Petten, Netherland and in Ispra, Italy. The framework for virtual integration of laboratories presented in this study is applied for co-simulation of transmission and distribution systems. [ABSTRACT FROM AUTHOR]

System frequency may change from defined values while transmitting power from one area to another in an interconnected power system due to various reasons such as load changes and faults. This frequency change causes a frequency error in the system. However, the system frequency should always be maintained close to the nominal value even in the presence of model uncertainties and physical constraints. This paper proposes an Active Disturbance Rejection Controller (ADRC)-based load frequency control (LFC) of an interconnected power system. The controller incorporates effects of generator inertia and generator electrical proximity to the point of disturbances. The proposed controller reduces the magnitude error of the area control error (ACE) of an interconnected power system compared to the standard controller. The simulation results verify the effectiveness of proposed ADRC in the application of LFC of an interconnected power system. [ABSTRACT FROM AUTHOR]

Graphical user interfaces have been progressively used in the classrooms to provide users of computer simulations with a friendly and visual approach to specify all input parameters with enhanced configuration flexibility. In this paper, an educational software package called PowSysGUI (Power System GUI), which runs on MATLAB and uses graphical user interfaces, has been developed for analysis and simulation of small to large size electric power systems. PowSysGUI is open-source software and anyone can see the inner structure of the program to figure out how to code a power engineering problem. It is designed as a simulation tool for researchers and educators, as it is simple to use and modify. PowSysGUI has algorithms for solving power flow, small signal stability analysis, and time-domain simulation. In the case studies, IEEE 16-machine 68-bus test system is given to show the features of the developed software tool. Moreover, classroom experience has shown that the developed software package helps in consolidating a better understanding of power system stability phenomena. [ABSTRACT FROM AUTHOR]

With the increasing occurrence of extreme weather events, the short circuit and line-breaking faults in transmission lines caused by line galloping have been threatening the security operation of power systems. These faults are also hard to be simulated with current simulation tools. A numerical simulation approach of power systems is presented to simulate the clustered, cascading faults of long-timescale caused by line-galloping events. A simulation framework is constructed in which large numbers of fault scenarios are simulated to reflect the randomness of line galloping. The interaction mechanism between power system operation states and line galloping processes is revealed and simulated by the solution of differences of timescales and parameters. Based on Power System Simulator/Engineering (PSS/E), an extended software package for line galloping simulation is developed with Python, which extends the functionalities of the PSS/E in power system simulation. An example is given to demonstrate the feasibility of the proposed simulation method. [ABSTRACT FROM AUTHOR]

Future power systems with high penetrations of variable renewables will require increased levels of flexibility from generation and demand-side sources in order to maintain secure and stable operation. One potential flexibility source is large-scale energy storage, which can provide a variety of ancillary services across multiple time scales. In order for appropriate levels of investment to take place, and in order for existing assets to be utilized optimally, it is essential that market signals are present which encourage suitable levels of flexibility, either from storage or alternative sources. Suboptimal storage plant dispatch due to uncertainty and inefficient market incentives are represented as operational constraints on the storage plant, and the impact of these inefficiencies are highlighted. Thus, changes required in operational practices for storage plant at different installed wind capacity levels, and the challenges that private storage plant operators will face in generating appropriate bids in a market environment at high variable renewable penetrations are explored. The impacts on system generating costs and storage profits are explored under different plant operating assumptions. [ABSTRACT FROM PUBLISHER]

Power systems require a certain amount of flexibility to meet varying demand and to be able to cope with unexpected events, and this requirement is expected to increase with the emergence of variable power generation. In this paper, we focus on gas engine power plant technology and the beneficial influence its flexible operation can have on a power system. The study introduces the concept of a combined-cycle gas engine power plant (CCGE), which comprises a combination of several gas-fired combustion engines and a steam turbine. The operation of CCGE is then comprehensively analyzed in electricity and reserve production in the South African power system and compared with combined-cycle gas turbine (CCGT) technology. Even though CCGE is a form of technology that has already been commercialized, it is rarely considered as a source of flexibility in the academic research. That is the notion providing the motivation for this study. Our core contribution is to show that the flexibility of CCGE can be valuable in power systems. The methodology is based on the unit-level model of the studied system and the solving of a day-ahead unit commitment problem for each day of the simulated 11-year period. The simulation studies reveal how a CCGE is able to offer system flexibility to follow hourly load variations and capacity to provide reserve power effectively. [ABSTRACT FROM AUTHOR]

With the emerging growth of high-voltage direct current (HVDC) transmission in modern power systems, the HVDC grid has become a hot topic in recent academic research and real projects. In the DC grid, DC faults can have very serious consequences, and so the faulty DC parts need to be rapidly isolated from the system. Compared to the full-bridge converters for the DC grid, DC circuit breakers are preferred to deal with this problem economically. In this paper, the self-excited resonant DC circuit breaker is reviewed. Then, a novel scheme of hybrid DC circuit breaker is introduced, and the operation principle of the proposed circuit breaker is described in detail. Finally, a four-terminal HVDC grid based on a modular multilevel converter (MMC) is used as the DC test system in PSCAD/EMTDC to verify the validity of the proposed DC circuit breaker. From the simulation results, it is seen that the proposed DC circuit breaker has advantages on current interruption time, voltage on DC circuit breaker, investment, etc. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The motivation and training of a proficient and diverse pool of power engineers, system operators, and policymakers is an important challenge for the electric industry. Power system experts are increasingly in demand globally to facilitate transitions to more environmentally friendly energy systems. More generally, citizens with a basic understanding of load balancing and renewable energy sources are more effective partners in increasingly complex power economies and political decisions. To address the need for an accessible general introduction to power systems, we are developing Griddle, an educational video game that introduces secondary school students to the basics of power system design, scheduling, and operation. We describe the design of Griddle's gameplay and underlying simulation, improvements made in response to user feedback, alignment with emerging teaching standards, and a high school classroom evaluation (n = 178) of Griddle's significant transformative impact, with the goal of validating the game-based learning approach and sharing “lessons learned” with designers of related tools. We find that Griddle is effective at engaging students and presents evidence that it helps students integrate key concepts, and we identify areas where further development and study are needed. [ABSTRACT FROM AUTHOR]

Real-time operation of electric power systems under high penetration of renewable energy generation has to incorporate strategies for managing the uncertainty associated with this type of power sources. In the case of the unit commitment problem, models based on robust optimization have been widely used for the day-ahead computation of power dispatch and reserves schedule. Typical approaches use uncertainty sets with fixed levels of conservativeness, without considering the real-time performance of the solutions. This paper proposes a solution scheme for the adaptive robust unit commitment problem using online adjusted data-driven uncertainty sets. Conservativeness parameters of the uncertainty sets are dynamically calculated as a function of previous operating results and incoming data via reinforcement learning, resulting in an online learning-optimization framework. The paper also develops an experimental framework to simulate real-time operation under the proposed methodology. Out-of-sample experiments illustrate the effectiveness of the proposed scheme against well-known benchmarks with fixed robustness levels. Results show improvements in power generation costs, voltage violations, and use of reserves. Two systems of different sizes are analyzed, illustrating the scalability of the proposed approach. • Q-learning algorithms for data-driven robust uncertainty sets adaptation. • Uncertainty sets dynamical adaptation based on real-time system indicators. • Novel framework for real-time power systems operation simulation. • Results comparison against two-stage robust and stochastic optimization approaches. • Statistically significant lower generation costs and use of system reserves. [ABSTRACT FROM AUTHOR]

In this paper, we present a scalable approach for real-time simulation of ship power systems with high-frequency power electronics converters (100–200 kHz). The proposed approach is based on the latency-based linear multistep compound method and relies on field-programmable gate array (FPGA) execution. Several examples of increasing dimension and complexity are used to evaluate the scalability—both of in terms of computational delay and of resources usage—of the proposed approach. Real-time execution with a 50 ns time step is achieved for all the examples considered. [ABSTRACT FROM PUBLISHER]