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Summary The power grid constructed with electric power router (EPR) will have the ability of flexibly controlling the voltage and power flow on each line of the grid, which will be helpful to maximize the integration of the renewable distributed generation to the grid. Most of the current methods for transmitting energy depend on storage unit or large scale calculation, which are relatively difficult. To avoid these disadvantages, this paper proposed a two‐step routing strategy based on the improved shortest path method for DC power grid with EPRs. The improved shortest path method combines Shortest Path Faster Algorithm (SPFA) with depth first search (DFS) algorithm, which could handle the negative weights and the negative cycle issue in the graph of the power flow paths. The increase of the transmission line power loss and the EPR's power loss are taken as the weight for the path search method to evaluate the cost of the path. Applying the proposed method to each power demand and supply finally helps to obtain the current distribution of the whole grid. By analysis of typical scenarios, compared with the power flow distribution of traditional DC power grid, the one produced by the proposed strategy could improve the power transmission capability as well as reduce the maximum voltage drop in the network. Besides, this strategy introduces less power loss, than many other ways do, in power routing. The effectiveness of the rioting strategy is related to the configuration of the network. [ABSTRACT FROM AUTHOR]

Fast and accurate fault location methods will accelerate power system restoration process and then cause improvement on availability and reliability indices. Presenting a modified scheme in order to improve accuracy of impedance-based fault location method in electric power distribution systems (EPDS) equipped with distributed generation (DG) units is the main goal of this paper. To achieve this goal, an iterative algorithm is introduced to compensate load variations. Also, a method is presented based on forward/backward sweep load flow to consider loss in all laterals of EPDS. Then, fault location will be determined by using a comprehensive method that extracts a fifth-order algebraic equation for each type of fault. This method will be modified to consider the presence of DGs in EPDS. In this paper, all the specific characteristics of real distribution systems such as unbalanced nature of network and loads, different types of loads, presence of multi-phase laterals, and capacitive effects of distribution lines are taken into account. The proposed scheme uses only 1 measurement unit at the main substation and 1 measurement unit at the DG bus. In this paper, modified IEEE 34 node test system is simulated by using PSCAD/EMTDC software, and it is used as a test system to evaluate the performance of the proposed method. Different scenarios such as the effect of fault distance, fault type, different fault resistances, and measurement unit errors are evaluated. The results indicate usefulness and precision of the proposed scheme. [ABSTRACT FROM AUTHOR]

A MicroGrid (MG) can be operated in two main situations: grid-connected mode and autonomous mode. Power electronics (PE) are required to interface the DG units with the MG. This paper presents an optimal operating strategy and cost minimization scheme for an electronically weak-coupled MG. The major objective of the paper is to minimize the overall cost considering both the power system and the power electronics constraints in the two modes of operation. The paper presents steady-state models of power electronic converter/inverter systems for coupling distributed generation (DG) units to the grid based on Newton-Raphson method. A Matlab program is developed to represent the proposed algorithm. The program is tested in various network conditions and verified by applying it to an MG with three different DG units. The main contribution of the study is to ensure that the converter constraints are satisfied for both types using DC/AC inverter and AC/AC matrix converter. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: In recent scenario, there is abundant availability of renewable energy resources to satisfy the significant increase in residential, industrial, and commercial demand. This paper presents a novel framework to determine the preeminent size of renewable distributed generators (RDGs) by optimizing the system components such as area required for solar‐photovoltaic modules, swept area occupied by wind turbine blades, and area used by fuel cell. A microgrid with hybrid RDG (h‐RDG) is integrated in distribution system to minimize the distribution loss, substation energy requirement, and improve the voltage level of the load. The power loss minimization is formulated as a nonlinear problem and optimized by the proposed Hybrid Nelder Mead‐Particle Swarm Optimization algorithm. The microgrid location is identified by voltage stability index to improve the stability of system. Further, the system is analyzed for energy flow in different seasonal loading conditions with mixture of residential, industrial, and commercial load. The effective performance of the proposed technique is applied to standard 12‐bus, 69‐bus, and a practical Tamil Nadu (TN) 84‐bus radial distribution system (RDS) for different hybrid combinations of h‐RDG in microgrid. The result proves that the proposed method provides a simple and efficient tool for optimal and flexible use of h‐RDG in microgrid under different climatic changes by simultaneously reducing distribution energy loss and improving voltage profile. [ABSTRACT FROM AUTHOR]

In recent years, Distributed Generation (DG) has been utilized in electric power networks increasingly. DG units can affect the system operational conditions in different ways such as voltage profile improvement, amending voltage stability, reliability enhancement, securing power market, etc. if they are managed properly. Otherwise, they may have undesirable impacts on technical issues of power grids. A lot of studies have been done on various aspects of control and operation of DG units to find the optimal placement, sizing and also the proper technology of them. This paper proposes a novel comprehensive economic method for planning DG units which considers both the Distribution Company's (DisCo) and the DG Owner's (DGO) profits simultaneously. Multi-objective particle swarm optimization technique is used to simulate many case studies on the IEEE 33-bus distribution test system and finally find the best solution for the placement, size and contract price of the generated power of DGs. The proposed methodology not only considers operational aspects such as power loss reduction, voltage profile and stability improvement and reliability enhancement, but also leads to an accurate analysis which satisfies both the DisCo's and the DGO's economic viewpoints. Finally, an encouragement to invest more on DG technologies is proposed based on the gained results. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Industrial plants/commercial facilities with synchronous generation, seek reliable and continuous operation even at the time of grid outages. Thus, islanding detection methods have been proposed in the literature that can be used to change the operating mode of the employed distributed generators from grid-parallel to stand-alone. Among the few solutions previously presented for switching the control mode in the reverse event of reconnecting to the grid, the method presented in this paper is unique. This grid-reconnection detection technique is low cost, fast, and does not interact with the power quality of the island although it only uses one, locally measured, variable. The method implies processing of oscillatory modes in frequency signal and is independent of the autonomous island's boundary. The investigation also includes a discussion on similar event of merging of adjacent islands. Simulations confirm the successful discrimination between reconnection event and other switching/power quality events. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a new synchronous reference frame theory–based power angle control (PAC) method for unified power quality conditioner with distributed generation (UPQCDG) is proposed for effective grid integration of solar PV. In UPQCDG, shunt active power filter (APF) feeds power from distributed generator to load, apart from supplying reactive power demand, which leads to increase in VA burden, hence its rating. Power angle control method aims at effective utilization of series and shunt APFs through sharing of reactive power to reduce VA burden on shunt APF. Proposed PAC method is based on instantaneous three‐phase power estimation technique, which is simple and robust and utilizes already available measurements of UPQCDG. Performance of proposed system is tested in the presence of nonlinear and reactive loads with solar PV generation system. Dynamic performance of system is studied during grid disturbances such as voltage sag and swell, solar irradiation variation, and change in load. Effectiveness of proposed method is validated using real‐time simulation performed in Opal‐RT, in which electrical circuit of UPQCDG is simulated on FPGA computation engine with submicrosecond time step to emulate real hardware closely. [ABSTRACT FROM AUTHOR]