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Summary: The purpose of this paper is to present a model for optimal placement of distributed generation units and sectionalizing switches (relocation of the existing switches and installation of new ones) to increase distribution network resilience against the threat of transmission system outage. The proposed model is formulated as a multi‐objective optimization problem with the objectives of minimizing investment costs and maximizing load restoration. In this regard, distribution system operation during normal conditions as well as transmission system outages is considered. In addition, the unique characteristics of the real power grid in Khuzestan province in southwestern of Iran are addressed in the proposed model which makes the model applicable to the real networks with similar characteristics in many parts of the Middle East. This grid has two completely different load patterns (in terms of load curve shape and peak load) corresponding to two hot and temperate periods, which causes completely different concerns for the network's operator. The proposed model is solved using multi‐objective genetic algorithm (NSGA‐II), and it is implemented on the 33‐node test system and the results are analyzed. Moreover, it is applied to the 327‐node real‐world test system in Khuzestan province to demonstrate its applicability to large networks. In both cases, the results confirm the effectiveness of the proposed optimization model. [ABSTRACT FROM AUTHOR]

Summary: Enhancing distribution system operation accomplished with the integration of renewable energy resources (RERs) has several technical, economical, and environmental dimensions. In this regard, this paper presents an optimal integration procedure of Distributed Generation (DG) based on Photovoltaic panel (PV) and Distribution Static Compensator (DSTATCOM) in Electrical Distribution System (EDS). The proposed procedure is formulated as a multi‐objective function (MOF). The considered objectives that reflect the technical, economic, and environmental issues, are Active Power Loss Level (APLL), Short Circuit Level (SCL), Voltage Deviation Level (VDL), Net Saving Level (NSL), and Environmental Pollution Reduction Level (EPRL). The proposed procedure investigates several hybrid optimization methods that combine the firefly algorithm (FA) with various acceleration coefficients PSO algorithms to improve the overall solution quality of the hybrid algorithms compared with the individual algorithms. To prove the capability of the proposed procedure, four different cases are tested on IEEE 33‐bus and 69‐bus EDSs. Added to that, the proposed algorithms are extended to practical Algerian EDS in Adrar City 205‐bus. Results obtained by the hybrid FA‐SCAC‐PSO algorithm showed that the simultaneous allocation of multiple DG and DSTATCOM in all standard and practical test systems significantly reduces the loss and enhances the voltage profile. An energy‐efficient analysis to proceed for different cases studied based on the best hybrid FA‐SCAC‐PSO algorithm to reach the best value of MOF compared to other algorithms, moreover the capability to achieve the optimal allocation of DG and DSTATCOM by maintaining the voltages profile within the permissible limit, whatever the variation of load. Significant technical economic and environmental achievements are found for different case studies especially in the existence of DGs and DSTATCOM devices. [ABSTRACT FROM AUTHOR]

Summary: This article presents a direct power control (DPC) method to cover entire power limit area (PLA) of grid‐connected converter for Distributed Generation (DG) application. By using of the Lyapunov theory, an online decision‐making process is designed in which the optimum switching state of converter is determined only based on interactions between grid/converter voltages and power errors. The proposed method neither needs small sampling time nor system's parameters. In this paper, two major tracking indexes are evaluated throughout PLA: apparent power error and average switching frequency. This evaluations lead to a better analysis of the controllers' behavior across the entire operation range (ie, PLA). Effects of different sampling times and parameter mismatch are depicted in the results, which indicate optimum and reliable performances of the proposed method. [ABSTRACT FROM AUTHOR]

An essential part of the smart grid development is to connect the main transmission grid with microgrids that consist of distributed generation resources. The integration of microgrids and the transmission grid not only can improve the reliability of the power system operation but also can increase the competition of the electricity market. The effective trading between microgrid agents and a distribution company (DisCo) is consistent with the direction of smart grid development. Developing effective strategy to optimally schedule energy trading between microgrid agents and the DisCo will bring benefits to all parties and promote further development of distributed clean energy. By analyzing the operation characteristics of the electricity market with the addition of microgrid agents as new market participants, this paper presents a bi-level optimization model that aims to maximize the benefits of microgrid agents and a DisCo while considering transmission loss factors from various generators, duality role of the microgrid agents who can either buy electricity from the wholesale market at volatile prices or sell electricity into the market or to its local consumers. The model presented in this paper jointly optimizes the energy schedules of the microgrid agents and the DisCo and determines the bid/offer price at which the microgrid agent buys and sells electricity from/to the DisCo. At last, simulation results are provided to demonstrate the feasibility and application of the proposed two-level optimization model. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a proportional nucleolus game theory (PNGT)–based iterative method has been presented to compute locational marginal price (LMP) at buses where distributed generation (DG) units were installed in a distribution network. Proportional nucleolus theory is one of the solution concepts for a cooperative game theory problem. The PNGT‐based iterative method provides financial incentives in terms of LMP to DG owners as per their contribution in loss reduction and emission reduction at a particular loading on the distribution system. In this method, LMP values depend on the distribution company's decision maker's preference among loss reduction, emission reduction, and distribution company's additional benefit. This proposed PNGT‐based iterative method has been implemented on a Taiwan power company's distribution network consisting of 84 buses with 15 DG units using MATLAB. The computed LMP values have operated the network based on decision‐maker priority so as to enable fair competition among DG owners. [ABSTRACT FROM AUTHOR]

Distributed generation (DG) units are increasingly installed in the power systems. Distribution companies (DisCo) can opt to purchase the electricity from DG in an energy purchase contract to supply the customer demand and reduce energy loss. This paper proposes a framework for optimal contract pricing of independent dispatchable DG units considering competition among them. While DG units tend to increase their profit from the energy purchase contract, DisCo minimizes the demand supply cost. Multi-leader follower game theory concept is used to analyze the situation in which competing DG units offer the energy price to DisCo and DisCo determines the DG generation. A bi-level approach is used to formulate the competition in which each DG problem is the upper-level problem and the DisCo problem is considered as the lower-level one. Combining the optimality conditions of all upper-level problems with the lower-level problem results in a multi-DG equilibrium problem formulated as an equilibrium problem with equilibrium constraints. Using a nonlinear approach, the equilibrium problem with equilibrium constraints problem is reformulated as a single nonlinear optimization model, which is simultaneously solved for all independent DG units. The proposed framework was applied to the modified IEEE 34-bus distribution test system. Performance and robustness of the proposed framework in determining econo-technically fair DG contract price has been demonstrated through a series of analyses. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Connection of distributed generation to the grid and the expansion of transmission system in order to meet the growing for electricity are causing the extent and complexity of the network structure. The occurrence of fault in such networks leads to flow large short circuit currents through the system, which may exceed the rating of existing circuit breakers and can damage system equipment. The utilization of fault current limiters (FCLs) in power systems can be an effective method to limit fault currents. FCLs can offer many benefits, but these benefits depend on the number, installation location, and impedance of FCL. In this paper, determining the number, location, and impedance of FCLs in network is modeled as a new optimization problem when objective functions are reliability, power loss, and economical use of FCLs. Also, a combination of discrete and continuous particle swarm optimization algorithm is employed to solve problem. Modified RBTS 2 bus test system is considered to evaluate the effectiveness and feasibility of the proposed method. Obtained results show the importance of finding optimum number, location, and impedance of FCLs in minimization of the proposed objective functions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Power system dynamic equivalence, which has been developed to overcome the computational issues, is faced with new challenges by emerging distributed energy resources (DERs). The switching characteristic between DERs operational modes beside non-dispatchable inherent, that is, generation uncertainties, should be take into account in power system dynamic equivalencing. This paper proposes a switching-based dynamic equivalence modeling for power system considering DERs. Prony analysis is employed to fit a reduced-order model to a high-order system in frequency domain. The developed modelling strategy consists of high and low frequency equivalences. When the external system reconnects to the main network through the breaker, high-frequency equivalence is replaced with external system. This period contains 4 cycles for communication delay beside 5 cycles governor time constant, which give rises to a six-order equivalence model. Afterwards, a four-order low-frequency equivalence model is fitted to the external system in the connected grid mode. Accuracy of the fitted dynamic equivalences is investigated by calculating the mean square error between the measured signal and the Prony approximated one. A synchronous-based DER, a doubly-fed induction generators and a fuel cell DER are added to the CIGRE benchmark in order to analyse the proposed dynamic equivalence modelling. Simulation results demonstrate that the proposed equivalence modelling could exhibit the same results as the real external system in the frequency domain. Simulation results also reveal that increasing penetration of DERs affect the dynamic equivalence in grid-connected mode by degrading the higher frequencies while it has no impact on transient period equivalence. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Recent research indicates that future power networks will witness a major enhancement in renewable energy–based distributed generation (DG). The impact of DG and distribution management system (DMS) action can be directly and easily implemented in the distribution networks for the improvement of its voltage security states. In the first phase of this paper, the voltage security state of the distribution network is identified using combined Kohonen's self‐organizing feature map (SOFM) and learning vector quantization (LVQ) algorithm. Two indicators namely voltage stability index (VSI) and distribution system stability indicator (DSSI) are used in this paper for verification of classification result. To ensure voltage security, it is essential to improve the voltage profile of the system. In the next phase, genetic algorithm (GA) and spider monkey optimization (SMO) techniques have been applied to find the optimal location and size of DG for voltage security state improvement of the reconfigured distribution system. Accurate allocation of DG can help in demand side management (DSM) for providing better service to the consumers in real time in smart grid scenario. This methodology has been tested on IEEE 33 bus, IEEE 69 bus, and Indian 85 bus practical radial distribution system. Result shows that the proposed methodology can successfully and appropriately identify the voltage security states of power system by combined SOFM and LVQ algorithms, and utilization of suitable amount of DGs at best locations as obtained from SMO algorithm can improve the operating states of distribution network in terms of voltage security. [ABSTRACT FROM AUTHOR]

Summary: This paper presents an efficient framework for power loss reduction (PLR) in distribution networks. The aim of the suggested PLR model is to maximize the benefit earned for every dollar annually paid for the PLR purposes. As a main contribution compared with other works in the area of PLR, the budget constraint is incorporated with the presented model. Furthermore, in this paper, 4 potential alternatives implemented for PLR including distributed generation installation, network reconfiguration, distribution feeders' reinforcement, and installation of capacitor banks are simultaneously employed and subsequently, the optimum portion of each, based on the considered budget limitation, is determined. To solve the formulated PLR model, the integer‐based particle swarm optimization algorithm is utilized. The suggested PLR model together with integer‐based particle swarm optimization has been implemented in MATLAB programming environment structurally integrated with DIgSILENT software. Additionally, simulations are carried out on 2 distribution systems encompassing the IEEE 33‐bus and a 94‐bus real‐world distribution system. The obtained results for both of distribution systems demonstrate that the variation in limitation of budget can change the portion of each of 4 loss reduction alternatives and also the benefit received versus each dollar of annual expenditure. Furthermore, it is comprehended that the more than enough growth in investment cost can potentially decrease the benefit earned versus each dollar of annual cost paid for the PLR implementation. [ABSTRACT FROM AUTHOR]

Summary: Connection of distributed generations (DGs) to distribution networks changes their radial construction to mesh type and increases fault current level. In order to prevent over current relay tripping in case of out‐of‐zone faults, direction of faults must be determined. On the other hand, fault current limiters (FCLs) are a suitable technique to reduce the issue of fault current increasing. In this paper, it is confirmed that operation of FCLs affects voltage and current signals, drastically. Since fault direction is detected by directional relays using these signals, hence, FCLs can affect the performance of the relays. In the other hand, if the added DG is a wind turbine, it may affect the directional relays performance due to intricate fault behavior of wind turbines. To investigate the mentioned hypothesis, some of directional relaying algorithms are evaluated in presence of wind turbine and FCL. [ABSTRACT FROM AUTHOR]