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The paper proposes a new stochastic multiobjective technoeconomic model for integrating photovoltaic (PV) and wind energy resources in electricity price (EP)‐driven distribution systems. The primary goal of this paper is to determine the optimal location and capacity for renewable energy‐based distributed generation, specifically PV and wind resources, while considering weather and system uncertainties. These uncertainties include stochastic variations in PV illumination intensity, wind speed, EP, and load fluctuations. To address these uncertainties, the paper employs scenario modeling techniques named as Latin hypercube sampling with Cholesky decomposition. This technique generates multiple correlated scenarios that represent uncertain variables. Subsequently, a scenario reduction technique is applied to identify the scenario with the highest probability. Later, a mathematical model is developed to minimize an objective function that encompasses various factors like system losses, node voltage deviations, the cost of purchasing power from the grid; and simultaneously maximize the total annual energy savings. The objective is to find optimal solutions that strike a balance between different objectives. To obtain an efficient optimum solution, this paper employs an effective meta‐heuristic technique named as JAYA algorithm. The results obtained by the JAYA algorithm are juxtaposed with those obtained using particle swarm optimization and genetic algorithm techniques. The proposed method is evaluated using Institute of Electrical and Electronics Engineers (IEEE) 33‐node and IEEE 69‐node test feeders to validate its feasibility and effectiveness. However, the effectiveness of the proposed method is not limited to any size of test systems. [ABSTRACT FROM AUTHOR]

This article explores the impact of electric vehicle (EV) charging on power systems and emphasizes the importance of careful analysis and planning. It discusses various topics related to EV charging, including EV hosting capacity, optimal placement of EVs and charging stations, technical impacts of Vehicle-to-Grid (V2G) technology, shared vehicle rental, decentralised collaboration frameworks, intelligent energy management schemes, EV demand response, and optimal sizing and siting of public EV charging stations. The article provides valuable insights and solutions for utilities, academia, and policymakers to address the challenges and opportunities associated with EV charging. Additionally, the article introduces a new approach for determining the limits of transformers and overhead lines in relation to EV charging, using Monte Carlo simulations and proposing new parameters for evaluating maximum demands. The authors stress the need for further analysis and attention to the impact of EVs on power systems. [Extracted from the article]

This paper proposes a new comprehensive load restoration (LR) method for electrical distribution networks. Since two main technologies of switching equipment are there in the modern distribution networks, namely manual switches (MSs) and remote‐controlled switches (RCSs), this article has benefited from this concept effectively. A two‐stage algorithm that provides the system operators with the ability to recover part of the loads in the shortest possible time by RCSs is proposed. After this step, the remaining loads will be restored by a combination of MSs and RCSs. The other strength of this algorithm is to provide accurate and practical solutions so that the sequence of switching actions is clearly defined. Also, using an innovative index called expected weighted energy not supplied as the objective function of the main problem will ensure the operators recover the maximum amount of load in the shortest time possible. This novel method was applied on a sample standard IEEE distribution test network. The simulation results proved the effectiveness of this proposed method. [ABSTRACT FROM AUTHOR]

We report on the potential of today's LED technologies to approximate Spectral Power Distributions (SPDs) aimed at optimizing specific performance goals. We compare numerically optimal SPDs to actual SPDs produced by a 16-channel LED light source, aiming at optimizing performance for six different applications. These theoretical and practical limits of the potential of current LED technologies can serve as guidelines for the design of future LED sources for different applications. [ABSTRACT FROM AUTHOR]

Transmission lines, the core part of the transmission and distribution system in the smart grid, require effective, efficient, and reliable protective measures against faults to avoid severe damage to physical infrastructure and financial losses. Due to their growing popularity, machine learning models are used in fault detection and classification, whose performances can be severely affected by cyber‐attacks due to their data dependency, posing a critical concern. Hence, this paper introduces false data injection attacks to address the vulnerability of machine learning‐based fault detectors and classifiers. A comparative study of 9 detection models and 6 classification models under normal conditions and during a combination of two models of false data injection attacks is presented to evaluate the severity of cyber‐attacks. Experimental results show that highly accurate models in normal conditions are more susceptible to cyber‐attacks, with up to 69% and 28% degradations in accuracy for fault detectors and classifiers, respectively. Furthermore, the detection models are found to be more vulnerable to cyber‐attacks than the classification models. With no robust detectors and classifiers being found, this work addresses the importance of developing attack‐resilient fault detection and classification schemes considering their academic and industrial significance. [ABSTRACT FROM AUTHOR]

This paper presents a non‐intrusive method for identifying the load state of a distribution network. The method focuses on continuously varying loads. By considering the load on‐off state switching points and the continuous features at on state, a deep convolutional method considering non‐local spatiotemporal features is proposed. The addition of an attention component to the convolutional network enhances the non‐local feature extraction capability of the convolutional network. Ultimately, the effectiveness of the method is demonstrated in an experimental setting. In addition, this paper demonstrates that the proposed method can effectively integrate switching point features as well as persistent features through neural network visualization techniques. [ABSTRACT FROM AUTHOR]

As the most promising alternative to internal combustion engines (ICEs), electric vehicles (EVs) have an excellent development outlook. The charging route scheduling of EVs can simultaneously affect traffic congestion in the transportation network (TN) and power flow distribution in the power distribution network (PDN). The research on TN and PDN coupling networks based on the static traffic flow model is relatively mature; however, it ignores that the traffic flow will spread across periods in a short scheduling period. In this paper, a semi‐dynamic traffic flow model is proposed to represent the dynamic propagation characteristics of EVs and ICEs flow. Furthermore, the cost of carbon emission and system operation are combined as the overall goal of system optimisation. Since the model has become a more complex non‐linear model, this paper proposes to combine the heuristic sequential boundary tightening and binary expansion method to linearise the model. The study compared four cases and found that a 20% penetration rate of EVs can reduce carbon emissions by 4.2% while reducing the system's total cost by 10%. Moreover, the impact of network congestion on the spatiotemporal distribution of traffic flow and power flow in the coupled network is alleviated. [ABSTRACT FROM AUTHOR]

Virtual synchronous generator technology can effectively improve the anti‐interference characteristics of the system frequency and bus voltage in the microgrid, and solve the problems of insufficient damping and low inertia of the system. However, in an islanded microgrid with multiple distributed generation, the difference in line impedance will cause local voltage deviations, which in turn leads to a series of problems, such as reducing power distribution accuracy and increasing bus voltage drop. Therefore, for the island‐type microgrid multi‐inverter distributed power generation parallel system, in order to solve the problem of low power distribution accuracy and large frequency oscillation caused by system parameters in virtual synchronous generator control, an improved virtual synchronous generator control algorithm based on adaptive droop coefficient is proposed in this paper, which not only eliminates the resistance component of the line impedance, makes the system impedance characteristic present a purely inductive nature, but also realises real‐time adjustment of active and reactive power. While maintaining the stability of the bus voltage and system frequency, it maintains high power distribution accuracy and improves the dynamic performance and operational stability of the power grid system. [ABSTRACT FROM AUTHOR]

Voltage‐controlled voltage‐source inverters (VVSIs) have been widely used in microgrids. Typically, LC filters are adopted by the VVSIs to improve the quality of the output voltage. Resonances of the LC filters that may cause oscillations to the VVSIs can be damped by well‐designed voltage controllers. However, the virtual inductance (VI) that is widely applied to improve power sharing between VVSIs will reduce the stability margin of the voltage control loop and introduce new oscillations on the LC filters even if the well‐designed voltage controllers have been used, which has not been reported in the literature. Furthermore, since the VI will introduce a cross‐coupling into the system, the conventional methods for analyzing the resonances of the LC‐filtered VVSIs cannot be used for analyzing the oscillations caused by the VI. Therefore, the stability of the LC‐filtered VVSI with the VI is investigated based on a new model proposed in this paper. Besides, to enhance the stability of the VVSI, the application of a low‐pass filter or a band‐pass filter in the VI is studied. Moreover, when connecting the VVSIs, the effects of the line impedance on the stability of the VVSIs while using the VI are investigated. Finally, simulation and experimental results have been provided, which verifies the correctness of the analysis in this paper. [ABSTRACT FROM AUTHOR]

Due to the strong dependence between electricity generation and heating supply and the need for optimal use of renewable energies to supply power and heat loads, it is essential to provide an integrated energy management structure for electricity and heating systems. This paper studies the techno‐economic and environmental aspects of a combined electricity distribution and district heating system by considering multi‐type flexible energy resources and the environmental and practical constraints of both networks. The integrated energy system (IES) is equipped with wind power plants, combined heat and power plants, gas boilers, heat pumps, multi‐energy storage systems, electric vehicle parking lots, and multi‐energy demand response, as well as the IES operator can take part in the energy market to supply thermal and electrical demands. Besides, a robust strategy is adopted to control the power price uncertainty in the day‐ahead scheduling of IES, where a robustness parameter is considered to adjust the risk level of scheduling. The numerical results show that technical and environmental constraints can significantly increase the operation cost of IES by 11.8% and 3.6%, respectively. In addition, multi‐type flexible resources can improve the operational flexibility of IES by 16.1%. [ABSTRACT FROM AUTHOR]

The UHV DC tension insulator strings are often large‐tonnage suspension porcelain or glass insulators with high mechanical strength. The single insulator is heavy, so two workers working at the same time are required to make a replacement on insulator strings in live working conditions. One of the key problems that must be solved in live working conditions is to select an appropriate way to reach the working position and realize the potential transfer between two workers. In this paper, the electric field calculation model of live working of ±800 kV tension strings was established. The process that two workers enter and leave the working position along the tension string and different conditions that two workers replace insulators were simulated and analyzed, and distribution characteristics of the electric field of insulator strings and live workers were obtained. According to the calculation results, when the two workers replace the tension insulators in different tension strings, it is easy to realize the potential transfer, so as to reach the same potential for work. The study results of this paper provide a basis for the selection of replacement method of large‐tonnage single insulator by two workers, and a theoretical basis for UHV DC live working. [ABSTRACT FROM AUTHOR]

This paper deals with power generation through solar photovoltaic (SPV) system and its implementation as grid‐tied and stand‐alone systems. The major setbacks of SPV system of low conversion efficacy, that can be enhanced through the maximum power point tracking (MPPT) algorithm. A modified incremental conductance (MIC), termed as error based incremental conductance MPPT, has been proposed, and its behaviour is comprehensively compared with classical perturb and observe (P&O) and incremental conductance (IC) techniques. Dealing with the on‐grid application of SPV system, maximum power obtained through MIC is fed to a three‐phase grid operating at unity power factor (UPF), and the quality of grid current is monitored. Further, the power obtained through MIC finds its application in designing an SPV‐diesel generator (DG) based hybrid renewable energy system (HRES) for areas either not connected to the grid or have insufficient fossils. The stochastic nature of source or uncertain load demand leads to deviation in system frequency. This paper proposes an intelligent, comprehensive supervisory optimal‐fuzzy‐proportional‐integral‐derivative (O‐F‐PID) controller for load frequency control (LFC). The performance of proposed O‐F‐PID controller has been vividly compared with the designed optimal‐PID (O‐PID) and conventional PID (C‐PID) controllers under varying source and load demand conditions. [ABSTRACT FROM AUTHOR]

The ever‐evolving electricity distribution network calls for new effective, transparent and fair market procedures to be implemented. This paper offers a systematic framework for real‐time trading in prosumer communities. A data‐driven robust optimization model that deals with uncertainty is proposed using the flexibility requirement envelope concept. Using machine learning techniques, high quality point and quantile forecasts are prepared to form the envelope. Next, this data is fed into the optimization problem to match the peers and the distribution grid, trading power, and flexibility in a short‐term look‐ahead horizon. To increase the quality of forecasts, a clustering approach accompanied by a pattern recognition machine is proposed to determine the cluster to which the recently observed net‐load data belongs. To provide forecasts, a forecasting machine is developed using a hybrid of tree‐based ensemble learning models, which provides intuitive, robust, and accurate results. Finally, the peer matching is done in a decentralized fashion using the alternating direction method of multipliers (ADMM), while each agent calculates its battery storage aging cost. Case studies demonstrate the hybrid model's capability in providing high quality power and flexibility forecasts compared to single models and ARIMA models and its positive impact on reducing the overall cost of the system. [ABSTRACT FROM AUTHOR]

State estimation (SE) is based on an iterative process for solving weighted least squares (WLS) via the so‐called normal equations (NE). This process is prone to numerical instability and may lead to an ill‐conditioned state estimator in many cases. Although several methods have been proposed in the past to deal with the ill‐conditioning problem in high‐voltage transmission systems, the SE stability of low‐voltage distribution systems remains a challenge due to fewer measurements and high R/X ratios. This paper highlights the main reasons for the ill‐conditioning problem and focuses on the impact of the R/X ratio of the distribution systems. NE‐based SE uses a comparatively simple algorithm with much lower storage size. Hence, this paper proposes a regularized version of the WLS state estimator to solve the problem of ill‐conditioning using an adjustable regularization parameter. Simulation results on U.K. 18‐bus and radial 33‐bus distribution systems show improved performance in terms of reducing the computational complexity, measurements redundancy, the impact of high R/X ratios and improving the accuracy and numerical stability of the SE solution. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper examines the distributional properties of univariate and linear composite measures of long bone asymmetry. The goal of this paper is to examine models that best fit the distribution of asymmetries with implications for the improvement of forensic pair‐matching techniques. We use the software R to model reference data (N = 2343) and test data (N = 71) as normal distributions, an exponential power distribution, and a skew exponential power distribution—the latter two include the normal as a special case. Our results indicate that the data best fit the latter two distributions because the data are nonnormal. We also show how asymmetry statistics that use absolute values of side differences can be fit as folded distributions. This obviates the need for empirical distributions or for transformations that attempt to convert nonnormal distributions to normal distributions. The results of this study lay the framework for improving pair‐matching methods that use comparative reference data. [ABSTRACT FROM AUTHOR]

The paper represents a comprehensive review of the wind farm layout and reliability assessment of the wind farm integrated electrical power system. The authors have done a review on the proliferation of renewable energy which raises the uncertainties in the electrical power system. The uncertainties including wind speed and wake effect are important to deal with when an isolated microgrid is considered. The scenario becomes vigilant when the wind farms are integrated with the main grid. Due to uncertainties, the study of reliability evaluation of a wind integrated power system would become significant to analyse the electrical power system behaviour effectively. So, the paper discusses the layout optimisation methods of wind turbines considering the uncertainty parameters, mainly the wake effect. In this regard, the different wake models and optimisation methods based on a single‐objective and multi‐objective functions are reviewed in detail with the proper comparisons. The paper serves as a better illustration of the competency of these optimisation methods on the optimal wind turbine location on a wind farm. Furthermore, the paper extends the view on the reliability and cost assessment, and reliability improvement techniques of the wind integrated power system. This article provides comprehensive information, yields an attractive and subsequent tool for research requirements for the researchers to design the wind farm layout, and assessed the reliability of a wind integrated power system. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive power sharing control method of parallel‐connected hybrid inverters in microgrid. Normally the AC microgrid is composed of hybrid inverters, other power generation equipment and some loads in parallel. Droop control or virtual synchronous generator is usually adopted to control parallel inverters, so the output power ratio between each inverter is fixed by droop parameters. The input of hybrid inverter is PV panel and battery, so the power output ability of each hybrid inverter is different because of the different PV panel capacity, illumination condition, battery capacity and battery state of charge. Hence, the output power of some hybrid inverters is short or redundant sometimes, which makes microgrid unstable or causes power generation restraints. It is necessary to recognize the actual power capacity of each inverter and control the output power reasonably. This paper analyzes the characteristics of parallel‐connected hybrid inverters with droop control in microgrid. An adaptive power sharing method is developed to identify the unbalanced between the each inverter on DC bus. By adjusting the droop parameters, the output power of each inverter is regulated where the controlled parameters are defined in system transfer function with an optimal target. Experimental tests are executed following the numerical simulation. The results show that the output power of each inverter can be adjusted adaptively according to the practical needs. The excessive power from one inverter can be absorbed by the others. Therefore, the stability and the power capability in the system are both ensured by adopting the proposed methods. The outcomes of the study provide a reference to the development of the adaptive inverter in microgrid. [ABSTRACT FROM AUTHOR]

This paper explores the application of several panel data models in measuring productive efficiency of the electricity distribution sector. Stochastic Frontier Analysis has been used to estimate the cost-efficiency of 59 distribution utilities operating over a nine-year period in Switzerland. The estimated coefficients and inefficiency scores are compared across three different panel data models. The results indicate that individual efficiency estimates are sensitive to the econometric specification of unobserved firm-specific heterogeneity. This paper shows that alternative panel models such as the ‘true’ random effects model proposed by Greene (2005) could be used to explore the possible impacts of unobserved firm-specific factors on efficiency estimates. When these factors are specified as a separate stochastic term, the efficiency estimates are substantially higher suggesting that conventional models could confound efficiency differences with other unobserved variations among companies. On the other hand, refined specification of unobserved heterogeneity might lead to an underestimation of inefficiencies by mistaking potential persistent inefficiencies as external factors. Given that specification of inefficiency and heterogeneity relies on non-testable assumptions, there is no conclusive evidence in favour of one or the other specification. However, this paper argues that alternative panel data models along with conventional estimators can be used to obtain approximate lower and upper bounds for companies' efficiency scores. [ABSTRACT FROM AUTHOR]

With the integration of more and more renewable energy generations (REGs), the structure of traditional distribution networks is hard to accommodate the volatile power injections of REGs. As a new power electronic device, soft open point (SOP) can be installed to control both active and reactive power flow among active distribution networks (ADNs). This paper presents a comprehensive optimization method for allocating SOPs within an ADN with high penetration of REGs. In order to find proper SOP candidate locations, a selection strategy based on two technical indices is proposed. To mitigate the risk of voltage violation caused by REG forecast errors and improve the adaptiveness of allocation results, a two-stage robust optimization model for SOP allocation is formulated to minimize the total cost of SOP investment and network operation. The proposed model is converted into a mixed-integer second-order cone programming (MISCOP) problem, which is then decoupled into a master problem of planning and a subproblem of operation and solved by column and constraint generation (CCG) algorithm. Simulation results show that the proposed method can effectively find the optimal SOP allocation schemes. Comparisons with different mathematical formulation and solution methods show the advantages of the proposed method. [ABSTRACT FROM AUTHOR]

The penetration of photovoltaic systems (PVs) to existing power grids is increasing as they are considered attractive options for electricity generation in distribution networks. This paper focuses on estimating the total power generated by a group of neighbouring PVs, spread over a distribution network using a single pyranometer for measuring the solar irradiance. A new empirical-based model that employs the Gene Expression Programming (GEP) technique is proposed to correlate the distribution of the PVs and the irradiance measured by the pyranometer and estimate the total power generated by the PVs. The geographic variability reduction index has been considered in developing the proposed model that also employs a Wavelet Transform technique to enhance its accuracy. The effective performance of the proposed model is validated using real data collected by the Solar Project at the University of Queensland, Brisbane, Australia. Results reveal that the proposed technique yields more accurate results when compared with other existing approaches in the literature. [ABSTRACT FROM AUTHOR]

All kinds of power interruption, which cause heavy economic loss to the electrical power company and users, occur in the operating process of distribution networks. Among them, stochastic line fault has a high probability of occurrence. Distributed generation (DG) as an environmental and independent power source has drawn worldwide attention. However, the introduction of DGs has brought increase in the number of system components and expansion of the scale of power systems, which make risk assessment and management more difficult. Therefore, a new method of risk assessment for power failure and control method of distribution network with DG based on stochastic lines failure is presented in the paper. In order to improve the accuracy and rapidity of evaluation, an assessment method with a new island partition strategy is proposed, in which two new parameters are defined to weaken the dependence on the network structure during the course of island partition. This paper also establishes a risk management model based on line maintenance and replacement for selecting an optimized risk management scheme, and applies the genetic algorithm (GA) to calculate the same. The presented method can provide the reference for planning and operating staff, and the example result proves its favorable guiding benefits. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In recent years, accidents involving windage yaw flashover have been occurring on transmission lines frequently, affecting the operational security and the power supply reliability seriously. Moreover, it is expensive and difficult to reduce the windage yaw flashover by modifying the towers and transmission lines. Therefore, a real-time alarm and dynamic early warning model for windage yaw of a cat-head type tower is proposed in this paper from the perspective of operation. Starting with the sidephase and the medium-phase conductors of the cat-head type tower, which are common and prone to accidents due to windage flashover, the windage yaw angle of the suspension insulator string in the real-time alarm is provided by the inclination angle measuring instrument, while in the early warning scenario that is calculated based on meteorological forecasting information. Then the minimum gap between the line and tower is calculated. Finally, the model issues windage yaw alarms or warnings by comparing the calculated minimum gap with the minimum permissible clearance corrected by rain density and gives the operations corresponding to each alarm and warning. The correct predictions in three time intervals and the feasibility of the model can meet the requirement of engineering application. Because of the limitation of the numerical weather prediction (NWP) model and accuracy, the prediction result is not very good when the time interval is long; it could improve the prediction result when more accurate NWP data is employed. [ABSTRACT FROM AUTHOR]

Abstract: A distribution network operator can reconfigure the network topology by operating section switches to improve multiple objective functions, that is, the line losses and the lifespan of transformers. In the context of long term network management, the impact of future electricity deregulation should be taken into account. Because the related literature has not addressed the above problems, this paper presents a multicriteria optimization approach for efficient distribution network management under electricity market deregulation. The main contributions of this paper can be summarized as follows: (a) the time‐variable (time dependent) and nonconvex issues for the distribution network management are formulated such that the time series variations of the line losses and the transformers mechanical operations are modelled, (b) an electricity consumption model under the deregulation, in which consumers flexibly respond to electricity prices, is taken into account, and (c) from the practical viewpoint, the proposed evolutionary many‐objective optimization approach is applied to find approximated Pareto optimal solutions of the nonconvex large‐scale problem within practical operating time. It can be seen from the computational experiment that the proposed method enables the network operator to easily identify a better network topology, which adequately meets the multiple requirements of the operator. [ABSTRACT FROM AUTHOR]

High penetration of power electronic devices and nonlinear loads can negatively affect the power quality of the distribution system. The conventional method of improving the power quality is to employ an extra distribution static synchronous compensator (D- STATCOM) or an active power filter ( APF) for compensating reactive power and mitigating current harmonics. This paper proposes an electronic power transformer ( EPT) without the aforementioned additional equipment, which can realize multi-function coordinated operation, including active power transmission, voltage conversion, reactive power compensation, and current harmonics suppression, based on the distribution system need. The multifunctional EPT consists of three stages, namely cascaded multilevel AC/ DC rectifiers, dual-active bridge ( DAB) converters with medium-frequency transformers, and DC/ AC inverters. The mathematical model of each stage is established and analyzed. Meanwhile, the control strategies of three stages are presented. Finally, a simulation model is built by MATLAB/ Simulink to demonstrate the effectiveness of the strategy and operating principle of the proposed EPT. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

With massive wind power integration, the spatial distribution of electricity load centers and wind power plants make it plausible to study the inter‐spatial dependence and temporal correlation for the effective working of the power system. In this paper, a novel multivariate framework is developed to study the spatio‐temporal dependency using vine copula. Hourly resolution of load and wind power data obtained from a US regional transmission operator spanning 3 years and spatially distributed in 19 load and two wind power zones are considered in this study. Data collection, in terms of dimension, tends to increase in future, and to tackle this high‐dimensional data, a reproducible sampling algorithm using vine copula is developed. The sampling algorithm employs k‐means clustering along with singular value decomposition technique to ease the computational burden. Selection of appropriate clustering technique and copula family is realized by the goodness of clustering and goodness of fit tests. The paper concludes with a discussion on the importance of spatio‐temporal modeling of load and wind power and the advantage of the proposed multivariate sampling algorithm using vine copula. [ABSTRACT FROM AUTHOR]

Combined heat and power (CHP) systems are employed to supply electrical and thermal loads of distribution networks (DNs). However, the heat loss can significantly hinder the heat transfer through pipelines from CHP systems to consumers Therefore, the optimal placement and sizing of CHP systems to reduce losses, including electrical and thermal losses, are very crucial. To minimize electrical loss, many methods have been proposed for optimal resource allocation. In this paper, a new approach for the optimal allocation of CHP systems to minimize electrical loss and heat transfer loss (HTL) is presented. Accurate modeling of HTL through the pipeline is performed. The proposed method is applied to 33‐bus, 69‐bus, and 84‐bus test systems. According to the simulation results, it is concluded that considering HTL in the resources optimization problem leads to major changes in the selection of CHP systems' optimal size and location. To solve the optimization problem, a new enhanced imperialist competitive algorithm (E‐ICA) is presented. The proposed algorithm enhances the performance and efficiency of the ICA algorithm by improving exploitation and exploration to prevent getting trapped in local optimums. Comparison of CHP systems allocation results confirms the superiority of the E‐ICA algorithm over other methods. [ABSTRACT FROM AUTHOR]

The article replies to the comments made by Ian Jones on the article "Distortions in Electricity Pricing in the UK." Jones raised a number of points, most of which the authors believe are tangential to the central argument of their 1983 paper. The article suggests that the issues involved are of considerable importance for electricity pricing policy. The authors emphasized that their paper focused on whether the Bulk Supply Tariff is being constructed in a consistent way, given the Central Electricity Generating Board's own declared policy of long-run marginal cost pricing.

The increasing integration of distributed photovoltaics may further aggravate the over‐voltage and three‐phase unbalance issues of low‐voltage distribution networks with three‐phase four‐wire structures. The voltage control method based on the AC and DC side power flow control and the three‐phase power control capability of voltage source converter in hybrid AC/DC low‐voltage distribution networks is a solution for the improvement of the above power quality issues. In this paper, an accurately improved sensitivity matrix calculation method considering shunt admittance based on the ABCD parameters is proposed in hybrid AC/DC low‐voltage distribution networks with a three‐phase four‐wire structure. The presented ABCD parameters of the feeders consider the influence of the coupling effect among phases and the neutral line on sensitivity calculation, which makes the sensitivity calculation simple. Then, a power‐voltage control method for voltage source converters based on three‐phase four‐wire sensitivity matrices of the AC side is proposed considering the constraints from the voltage source converter and DC side power flow in hybrid AC/DC low‐voltage distribution networks, which can effectively address the over‐voltage and unbalanced issues. Simulations are performed to verify the proposed sensitivity calculation method and voltage control method. [ABSTRACT FROM AUTHOR]

The virtual power plant (VPP) can aggregate small‐scale distributed resources to provide flexibility for the transmission system. The flexibility provision capability of the VPP is restricted by technical operating limits of the distribution system to which distributed resources are connected. To facilitate the flexibility provision of the VPP while securing the operation of the local system, this paper leverages the dynamic line rating (DLR) to enlarge the VPP flexibility region. The flexibility region of the VPP is defined as the allowable range of active and reactive power output that the VPP can execute subject to operating constraints of the internal system. With the DLR, the current carrying capacity of the distribution network is dynamically adjusted based on actual environmental conditions, which helps to remove barriers from transmission limits that hinder the integration of distributed flexibility. A convex hull‐based method with an explicit accuracy guarantee is proposed to approximate the flexibility region with the DLR. Case studies based on IEEE‐33 and IEEE‐123 test feeders with real‐world operation data validate the proposed framework. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to the problem of defining an investment policy in battery energy storage systems in active distribution networks, taking into account a diversity of uncertainties. The proposed methodology allows the selection of type, capacity, and location of battery energy storage systems in distribution networks with distributed generation and electric vehicle charging stations. A mixed‐integer stochastic programming problem is cunningly approached with a metaheuristic, where fitness calculation with stochastic scenarios is performed by introducing an approximation to the operation costs in the form of a polynomial neural network, generated according to the Group Method of Data Handling—GMDH method, with strong computing speeding‐up. The quality of this approximation for heavy Monte Carlo simulations is assessed in a first case study using a 33‐bus distribution test system. The optimization planning model is then validated in the same test system using real data collected from solar and wind sources, demand, prices, and charging stations. Four types of batteries are compared considering degradation impact. The results demonstrate the practicality and advantages of this process. [ABSTRACT FROM AUTHOR]

The electric power systems are experiencing a transformation to be characterized by power electronic devices, for example, voltage source converters (VSCs). However, the large‐capacity VSC will interact with the synchronous generators (SGs) and could lead to low‐frequency oscillation (LFO). It becomes a hurdle for the secure and stable operation of modern electric power systems. Therefore, this paper analyses the oscillatory instability mechanism of the SG with the penetration of grid‐forming (GFM) and grid‐following (GFL) VSC. The distinctive transfer function model of the SG‐VSC system is first developed. Then, through parameter sensitivity and transfer function analysis, the impact of three types of VSC is investigated, encompassing GFM‐VSC and GFL‐VSCs with two conventional reactive control schemes. It proves that the voltage control of the VSC can be detrimental to the damping torque of the SG. According to the theoretical analysis, a supplementary compensator is proposed to suppress the LFO induced by the VSC. Finally, case studies in a two‐area test system validate the analytical results and robustness of the proposed enhancement method. [ABSTRACT FROM AUTHOR]

For a few decades, electric power growth and demand have increased globally. To fulfil this demand, distribution generators (DGs) have been installed in the power system. To get numerous benefits such as comprising reduction of power losses, improvement of (voltage, current, rpm) transient stability, leads to economic benefits. DGs integration in the distribution power system (DPS) was reported as an optimal generator placement (OGP) problem to maximize these benefits. This paper performs wind turbine (WT) integration while considering the internal generator's (rpm) transient stability under fault conditions. A power loss index (PLI) method is implemented to select potential candidate buses for generator placement. A self‐sorting analytical approach (SSA) is also used to determine the optimal bus and WT size. The IEEE 14‐bus DPS is used as the OGP test system to demonstrate the proposed method's effectiveness in terms of power losses reduction, system transient stability, and economic benefits. The IEEE 14 Bus system was considered using MATLAB with a 3.2 GHz processor to perform the said approach. WT integration suggested in case‐2 results in a 65.80% power losses reduction, which leads to a 60.88% enhancement of economic benefits of the DPS. [ABSTRACT FROM AUTHOR]

We use World Wide Lightning Location Network (WWLLN) data on the radiated radio frequency electromagnetic energy per stroke to identify the upper tip of the global lightning stroke energy distribution. The mean stroke energy is about 1,000 J per stroke in the very low frequency band between 5 and 18 kHz, while the distribution used in this paper is limited to strokes in that band above 1 MJ, about 3 orders of magnitude above the mean. It is shown that these energies are representative of the tip of the optical distribution, first identified by Turman (1977) above 10 GW per stroke, which he termed "superbolts." The distribution peaks globally in the Northern Hemisphere winter (November–February) with most superbolts being found in the North Atlantic west of Europe, the winter Mediterranean Sea, and a strong local maximum over the Andes in South America. We identify regions with somewhat fewer superbolts in the North Pacific east of Japan in winter, along the equator of the Atlantic and Indian Oceans and south of South Africa. We find very few superbolts during April–October each year. While superbolts are scattered around the globe, the local occurrence peaks do not coincide with the usual three main lightning "chimneys." Unlike the distribution of all normal global lightning, we find superbolts predominantly over the oceans and seas, with fewer over the continents, just the opposite of all global lightning. Key Points: Superbolts, have more than 106 J of radiated VLF energy, which is comparable or larger than Turman'ssuperbolts with >10 GW optical powerSuperbolts dominantly occur during Nov‐Feb over water with peaks in the N. Atlantic and N. Pacific, the Mediterranean and over the AndesOne‐to‐one stroke comparisons with the Earth Networks Total Lightning Network show that all superbolts have peak currents over 105 A [ABSTRACT FROM AUTHOR]

The paper aims to propose an algorithm to calculate the power flow of an AC&DC hybrid distribution system. AC&DC distribution networks have recently attracted increasing attention, for the distributed generations (DGs) and DC loads can be integrated in DC networks in more simple and flexible ways than AC networks. Many efforts have been made to deal with the power flow problem of hybrid networks, however, the DC-side power flow's effect on three-phase unbalanced AC side and the influence to entire distribution system which DG directly connected in the DC side are both not considered. Therefore, this paper discusses the grid architecture with multiple AC&DC feeders. Then, models of VSC-MTDC, DC/DC converters, DGs, and other elements are formulated for power flow calculation. Furthermore, power flow equations of DC distribution and VSC converters are deduced in detail. As for converters under different control strategies and diverse forms of linking combinations between AC&DC grids, calculating approaches are considered to be of partial differences. Considering these distinct cases, a specific and improved sequential method is employed to compute distribution network's power flow. Simulation results on a modified IEEE 13 Node Test Feeder demonstrate the rapidity, accuracy, and easy-convergence of the algorithm. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of regulating the output voltage of a DC‐DC buck‐boost converter feeding a constant power load, which is a problem of current practical interest. Designing a stabilising controller is theoretically challenging because its average model is a bilinear second order system that, due to the presence of the constant power load, is non‐minimum phase with respect to both states. Moreover, to design a high‐performance controller, the knowledge of the extracted load power, which is difficult to measure in industrial applications, is required. In this paper, an adaptive interconnection and damping assignment passivity‐based control—that incorporates the immersion and invariance parameter estimator for the load power—is proposed to solve the problem. Some detailed simulations are provided to validate the transient behaviour of the proposed controller and compare it with the performance of a classical PD scheme. [ABSTRACT FROM AUTHOR]

As deregulation in the electric power industry has advanced in many countries, a spot market and a futures market for electric energy have already been formulated. In Japan, the foundation of a day-ahead spot market is scheduled for the 2005 fiscal year. This paper presents a method to evaluate the expected profit and risk for an electric power supplier considering both spot market and bilateral market. In this paper, the Vasicek model is used to represent the fluctuations in spot price and demand in a bilateral market, and additionally, Value at Risk (VaR) is used as a risk index. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(4): 1–11, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20515 [ABSTRACT FROM AUTHOR]

With the increasing penetration of large‐scale distributed renewable energies, the electricity distribution network is growing more complex with challenges brought by the intermittency and uncertainty of renewable energies. Microgrid (MG), one of feasible solutions to integrating renewable energies, has shortages because of limited capacity. Therefore, MG cluster (MGC) was proposed as an improved solution. To efficiently and friendly integrate renewable energies, a novel honeycomb‐like MG cluster (H‐MGC) is proposed in this paper. Considering the uncertainty of renewable energies, a robust optimisation method of the siting and sizing of energy storage system (ESS) constrained by emergency reserve is proposed. Combining the column‐and‐constraint generation algorithm and big‐M method, the proposed optimisation model is decomposed into mixed integer second‐order cone programming master problem and sub‐problems, which are alternately solved. Based on the optimal results of study case, the siting and sizing results of ESS are analysed, as well as the operating characteristics of H‐MGC. Compared to existing MGC system, the proposed H‐MGC has a more flexible operation mode. The related costs of ESS are reduced, and the operational life is relatively extended, under the condition that the emergency reserve of system is satisfied. [ABSTRACT FROM AUTHOR]

Power flow calculations are an essential stage in many planning and control applications for distribution systems.To use these in control applications, however, the calculation time needs to be improved, and this can be done by the use of a trained ANN. This paper presents the considerations for constructing ANNs for DSs, and describes a method for training the system in order to support switching events representing a change in topology. The solutions for three DSs, balanced as well as unbalanced, are presented and the various considerations affecting the most appropriate ANN construction are discussed. The results are compared to the solution from the classical complex Newton‐Raphson and the fixed‐point iterative methods. The solutions have very high precision and good results are found for switched laterals. The computational performance is also compared and an improvement of two orders of magnitude is observed. [ABSTRACT FROM AUTHOR]

With the advent of small‐scale heat and electricity producers in distribution energy systems, the interdependencies between energy carriers have been increased. Moreover, the rapid deployment of micro CHP, electric heat pumps, electricity‐to‐heat appliances etc., calls for new local market frameworks to be employed in distribution energy systems. In response, this paper presents a new energy market framework based on the concept of peer‐to‐peer negotiations to facilitate energy transactions between agents at the distribution level while addressing the interdependencies between different energy carriers. Moreover, linear optimization problems are proposed to investigate the optimal strategies of market participants with various configurations. These optimization problems not only obtain the optimum strategy of agents to participate in the day‐ahead peer‐to‐peer electricity market, the day‐ahead heat market, and gas distribution systems but also obtain their optimal operation scheduling for the entire next day. The numerical results successfully demonstrate the applicability and merits of the proposed market framework. [ABSTRACT FROM AUTHOR]

In a transmission line, sag is intentionally provided to relax the tension on the wire when placed between two terminals. However, thermal stress and extreme weather conditions can cause increases in transmission line sag, which can eventually damage transmission line infrastructure. In this regard, this paper examines a number of sag measurement techniques based on physical or optical properties and integrated with signal processing and communication technologies. The performance of different sag measurement methods is compared in terms of accuracy, precision and key feature. Several challenges and limitations of the existing sag measurement mechanisms are reported. A number of recommendations to address the identified challenges are made. Moreover, an efficient communication framework for sag related information exchange is proposed. This comprehensive review of the sag measurement techniques will facilitate the evolution of new and efficient real‐time sag measurement and monitoring methods. [ABSTRACT FROM AUTHOR]

Geomagnetically induced currents (GICs) are an impact of space weather that can occur during periods of enhanced geomagnetic activity. GICs can enter into electrical power grids through earthed conductors, potentially causing network collapse through voltage instability or damaging transformers. It would be beneficial for power grid operators to have a forecast of GICs that could inform decision making on mitigating action. Long lead‐time GIC forecasting requires magnetospheric models as drivers of geoelectric field models. However, estimation of the geoelectric field is sensitive to high‐frequency geomagnetic field variations, which operational global magneto‐hydrodynamic models do not fully capture. Furthermore, an assessment of GIC forecast uncertainty would require a large ensemble of magnetospheric runs, which is computationally expensive. One solution that is widely used in climate science is "downscaling," wherein sub‐grid variations are added to model outputs on a statistical basis. We present proof‐of‐concept results for a method that temporally downscales low‐resolution magnetic field data on a 1‐hr timescale to 1‐min resolution, with the hope of improving subsequent geoelectric field magnitude estimates. An analog ensemble (AnEn) approach is used to select similar hourly averages in a historical data set, from which we separate the high‐resolution perturbations to add to the hourly average values. We find that AnEn outperforms the benchmark linear‐interpolation approach in its ability to accurately drive an impacts model, suggesting GIC forecasting would be improved. We evaluated the ability of AnEn to predict extreme events using the FSS, HSS, cost/loss analysis and BSS, finding that AnEn outperforms the "do‐nothing" approach. Plain Language Summary: Forecasting space weather impacts on ground‐based systems, such as power grids, requires the use of computer simulations of the disturbance of the Earth's magnetic field by the solar wind. However, these computer simulations are often too smooth, underestimating small and fast variations in the Earth's magnetic field, which are important for modeling induction hazards that may affect power grids. In this paper we present a proof‐of‐concept scheme that attempts to introduce realistic high‐frequency variations using the idea of looking at how the field has previously behaved in historical events. We test the model and find that it allows for better impact forecasting than if our scheme is not used. Key Points: Operational global MHD models do not fully capture the ground‐level magnetic field variability important for modeling induction hazardsWe provide a proof of concept model to statistically introduce realistic, high‐resolution perturbations with which to drive an impacts modelOur downscaling scheme outperforms a reference linear‐interpolation approach under a range of metrics [ABSTRACT FROM AUTHOR]

A control strategy is formulated for photovoltaic generators (PVG) operating in parallel in a Microgrid. A radial microgrid is considered and when it is isolated from the utility grid, the PVG's must operate in the voltage-frequency control mode in the absence of a storage or a diesel generator unit. It is observed that the conventional P-f and Q-v droop control method fails to deliver correct power references for inverters operating in parallel when network impedance is unequal, and therefore an active power-reactive power-frequency-derivative (PQFD) droop control is proposed to achieve an error free power sharing. Seamless operation from the grid connected mode to isolated mode and vice-versa is achieved with the help of the aforementioned control, which in addition assists in the alleviation of sluggish response in the presence of Induction motor (IM) loads by providing appropriate damping. For a transient free transfer from isolated mode to grid connected mode, a synchronisation control is formulated which helps in the proper reconnection. The controller designed is tested in both Microgrid and the grid connected mode and during transition. The controller gains used in the paper have been obtained with the help of a small signal analysis of the system considered. [ABSTRACT FROM AUTHOR]

As installed wind generation capacity increases, understanding the effect of wind power on the electric power system is becoming more important. This paper introduces a statistical model that can be used to estimate the variability in wind generation and assess the risk of wind generation contingencies over a large geographical area. The analysis of the installed wind generation capacities is separated from the analysis of the spatial and temporal dependency structures. This enables the study of different future wind power scenarios with varying generation capacities. The model is built on measured hourly wind generation data from Denmark, Estonia, Finland and Sweden. Three scenarios with different geographical distributions of wind power are compared to show the applicability of the model for power system planning. A method for finding the scenario with the minimum variance of the aggregate wind generation is introduced. As the geographical distribution of wind power can be affected by subsidies and other incentives, the presented results can have policy implications. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper assesses the viability of providing down and up spinning reserves by renewable energy resources (RES) in island power systems. The process consists of evaluating the impact of providing spinning reserve on the system operation costs of different islands by simulating the unit commitment problem. The assessment is carried out for La Palma (small size) and Tenerife (medium size) island power systems, and by considering different wind source availability scenarios for sample weeks of different seasons in current and future years. This paper differentiates between up and down reserves and studies their impacts separately. Results show that enabling RES to provide just down spinning reserve has economic benefits for all scenarios, by reducing over 40% the amount of thermal generation and over 30% the systems costs for high wind scenarios. It also confirms that employing variable deloading of wind energy as a source of up reserve is advisable, mainly in scenarios with high share of wind sources. In some scenarios, using RES as reserve provider, reduces the amount of thermal generation more than 50%, compared to when RES does not participate as a source of reserve, and can even lead to a full RES coverage of demand. [ABSTRACT FROM AUTHOR]

This paper proposes a novel distributed bilayer coordinated control scheme (BCCS) to realize the autonomous economic operation of islanded hybrid AC/DC microgrids, which only requires a sparse communication link. In the lower layer, the optimal power reference iterative algorithm (OPRIA)‐based droop control is proposed to realize the economic dispatch of each subgrid individually, while the frequency of AC subgrid and the bus voltage of DC subgrid are regulated to their rated values. Then, the upper‐layer control for the interlinking converter is designed to achieve the global economic operation of the hybrid AC/DC microgrid through optimizing the exchanging power between AC and DC subgrids. The proposed BCCS has the advantage of reaching the economic operation and frequency/voltage regulation simultaneously for the hybrid AC/DC microgrid. Besides, the proposed BCCS realizes the stable and economic operation with less communication, flexible controllability, and good compatibility of renewable energy sources. Numerical simulation results based on Matlab/Simulink verify the effectiveness and excellent performance of the proposed BCCS even with the integration of renewable energy sources, and the test based on RT‐LAB illustrates the good real‐time performance of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a robust investment and operation model to attend the power and heat needs of a microgrid (MG) connected to the distribution system. The optimization algorithm decides on the best investment and operation of combined heat and power (CHP), boilers, PV power generation and battery energy storage systems (BESS). For the BESS, the algorithm estimates the optimal energy storage capacity (MWh) as well as the maximum hourly delivery capacity (MW). The non‐linear and non‐concave heat rate chart is recast by a mix‐integer linear model to have a tractable and precise model. The model considers the uncertain in some parameters using probability density function (pdf) to portrait its behavior. Thus, the problem has been modeled using stochastic programming approach, and its objective function is the expected value of the annual operational cost. The model is tested using a real case where two adjacent consumers share the power and heat facilities to minimize the overall up to 17% depending on the gas price scenario. The results demonstrate the benefits of employing different technologies and the synergies of all technologies operating together. [ABSTRACT FROM AUTHOR]

Classic droop control ensures the synchronization of distributed generation (DG) units inside a microgrid without requiring any deployment of communication links, however it causes unwanted frequency fluctuations and degrades system dynamics. Angle droop control and V−I control have been developed as two major global positioning system (GPS)‐based control methods, both of which realize a fixed‐frequency operation of the microgrid through synchronizing DG units with GPS timing technology and brings improvement to the dynamic response of the overall system. This paper reveals the similarities and the correlations between these two methods that they can both be regarded as different forms of virtual impedance control. A novel adaptive virtual impedance control method is proposed accordingly to generalize GPS‐based control strategies into a unified control frame. An impedance and inner controller design approach considering both stability constraints and power quality requirements based on the small‐signal model of GPS‐based microgrids is presented for practical implementation. An adaptive transient resistance concept is adopted to enhance the system stability during large disturbances and grid faults. Case studies are presented to validate the system performance and fault ride‐through abilities of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper describes line loss minimization control using the shunt and series converters of a UPFC (unified power flow controller) in a loop distribution system. The line losses in a loop distribution system are caused by the circulating current flowing in the loop and the mesh currents flowing to the loads. The authors have previously proposed a compensation method for circulating current using a series converter. In this paper, the authors propose a suppression method for reactive currents using a shunt converter. In the prototype model of a loop distribution system, a theoretical loss reduction ratio of 92% without line loss caused by active currents is obtained. Similar line loss reduction characteristics are obtained in experiments using the prototype distribution system. [ABSTRACT FROM AUTHOR]

Temperature has obvious effects on the tested results of frequency domain dielectric spectrum (FDS) method. To estimate the moisture content of field oil-immersed bushing, the effects of temperature must be considered and eliminated. In this study, the frequency-domain dielectric spectrum of 72.5 kV bushing samples with different moisture contents was tested at different temperatures. The law that temperature affects the results of FDS tests was analysed and concluded. Afterwards, a method to transfer the tested results to the reference temperature (15°C) was proposed. Finally, an estimation method of moisture content for field oil-immersed bushing was proposed and testified. The following conclusions can be concluded: (i) the effects of temperature on the FDS results may be divided into two aspects, i.e. one is along the horizontal axis and the other is along the vertical axis and (ii) based on the proposed method, the temperature effects on the results of FDS tests can be eliminated, and the moisture content of field oil-immersed bushing can be estimated effectively and feasibly. [ABSTRACT FROM AUTHOR]

Hybridization of energy sources provides better reliability and flexibility for the power generation system. To integrate different sources, a suitable power electronic interface and a power management strategy are mandatory requirements. In this paper, two types of dual‐input–single‐output DC–DC converters to integrate two different V‐I characteristic sources for DC microgrid application are presented. The analysis of the converters based on the voltage and current stress of the power switches available in the circuit has been carried out for the appropriate selection of power switches. The software simulation of the proposed converters is performed on a MATLAB/Simulink platform in a detailed manner, and an experimental prototype of the presented converters has been built to validate the simulation results. The experimental results are well matched with the simulation results, which demonstrate the efficient performance of the converters. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]