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Communication-based Adaptive Protection for Distribution Systems Penetrated with distributed generators

ELECTRIC POWER COMPONENTS AND SYSTEMS 2015年第5期43卷 556-565页

作者： Osman, Ahmed H. Hassan, Mohamed S. Sulaiman, Mohamad Amer Univ Sharjah Dept Elect Engn Coll Engn Sharjah 26666 U Arab Emirates

In this article, a communication-based adaptive over-current protection scheme for distribution systems penetrated with distributed generators is proposed. A communication network between the over-current relays, the distributed generators, and the utility grid is employed to automatically update the settings of the protective relays. Moreover, the communication reliability is increased through the addition of a backup communication system. The proposed scheme has the advantage of operating during grid-connected and islanding modes of operation. The scheme employs two simultaneous algorithms. The first algorithm works when the system configuration is changed due to the connection/disconnection of a distributed generator or the utility grid. The second algorithm efficiently uses the exchanged information between the relays to identify the faulted section and hence speeds up fault clearance. The proposed scheme is tested for difierent fault conditions as well as for different system configurations. The results demonstrated that relay operating times, including the communication delay, are greatly reduced when the faulted section is identified and relay settings are adjusted accordingly. In addition, a negligible time delay was experienced when the backup communication network was put in service.

关键词： distributed generators linear optimization power systems distribution system line protection communication systems directional relays adaptive protection multi-agent systems over-current relays

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GPU-based parallel real-time volt/var optimisation for distribution network considering distributed generators

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IET GENERATION TRANSMISSION & DISTRIBUTION 2018年第20期12卷 4472-4481页

作者： Huang, Shengjun Dinavahi, Venkata Univ Alberta Dept Elect & Comp Engn Edmonton AB T6G 2V4 Canada Natl Univ Def Technol Coll Informat Syst & Management Changsha 410073 Hunan Peoples R China

Although the wide integration of advanced metering infrastructure on distribution network facilitates the application of volt/var optimisation (VVO) in real-time circumstance, the contradiction between heavy computation load and low solution efficiency is still a big challenge, thus the system scales investigated in the literature are limited. In this study, the full AC real-time VVO is formulated based on particle swarm optimisation (PSO) framework and direct approach (DA) power flow method, where all components, such as distributed generator and on-load tap changer transformer, are formulated and integrated into the iterative DA process. Since both PSO and DA are suitable for parallel implementation, the graphics processing unit (GPU) is introduced for acceleration in order to achieve the possibility for real-time application. All the solution process is executed by GPU with the well-established data structure and thread organisation pattern, resulting in high efficiency by guaranteeing coalesced access within each warp. Case studies are conducted on four systems with sizes ranging from 136-bus to 1760-bus. Solution accuracy and convergence property are validated by the popular open source package Matpower. Based on the results from solution efficiency comparison between CPU sequential, CPU parallel, and GPU parallel programs, the promise of the proposed parallel implementation scheme for practical application is established.

关键词： distribution networks distributed power generation particle swarm optimisation graphics processing units parallel programming data structures load flow on load tap changers iterative methods public domain software software packages power engineering computing GPU-based parallel real-time volt-var optimisation distribution network distributed generators advanced metering infrastructure full AC real-time VVO particle swarm optimisation framework PSO framework direct approach power flow method DA power flow method distributed generator on-load tap changer transformer iterative DA process graphics processing unit data structure thread organisation pattern Matpower open source package CPU sequential program CPU parallel program GPU parallel program

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Determination of optimal sending voltage profile in distribution systems with distributed generators

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ELECTRICAL ENGINEERING IN JAPAN 2007年第2期161卷 16-24页

作者： Hayashi, Yasuhiro Matsuki, Junya Suzuki, Ryoji Muto, Eiji Univ Fukui Fukui 9108507 Japan

Sending voltage profile of distribution feeder is controlled by changing a tap of distribution transformer. In a distribution network with distributed generators, for reasons of effect of reversed flows from them and existence of a great number of sending voltage profile candidates, it is not easy to control sending voltage profile within the acceptable voltage limit. In this paper, in order to determine the optical sending voltage profile of distribution transformer in a distribution network with distributed generators, the authors propose a new method to determine the optimal sending voltage profile so as to minimize the total number of tap position's change per day under constraints of acceptable voltage limit. In the proposed method, after calculating acceptable range of three-phase voltage of distribution feeder, the optimal profile of tap position within the calculated acceptable voltage range is determined among these candidates by using reduced ordered binary decision diagram (ROBDD) which is an efficient enumeration algorithm. In order to check the validity of the proposed method, numerical simulations are carried out for a distribution network model with a distributed generator. (c) 2007 Wiley Periodicals, Inc.

关键词： control of sending voltage tap of distribution transformer distributed generators combinatorial optimization ROBDD

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A new approach based on ant colony optimization for daily Volt/Var control in distribution networks considering distributed generators

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ENERGY CONVERSION AND MANAGEMENT 2008年第12期49卷 3417-3424页

作者： Niknam, Taher Shiraz Univ Technol Dept Elect Engn Shiraz Iran

This paper presents a new approach to daily Volt/Var control in distribution systems with regard to distributed generators (DGs). Due to the small X/R ratio and radial configuration of distribution systems, DGs have much impact on this problem. A cost-based compensation methodology is proposed as a proper signal to encourage owners of DGs in active and reactive power generation. An evolutionary method based on ant colony optimization (ACO) is used to determine the active and reactive power values of DGs, reactive power values of capacitors and tap positions of transformers for the next day. The results indicate that the proposed encouraging factor has improved the performance of distribution networks on a large scale. (c) 2008 Elsevier Ltd. All rights reserved.

关键词： Ant colony optimization (ACO) distributed generators Voltage and reactive power control

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Convergence problem in forward/backward sweep power flow method caused by non-positive-sequence impedance of distributed generators and its solution

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2015年 65卷 463-466页

作者： Ju, Yuntao Wu, Wenchuan Zhang, Boming Tsinghua Univ Dept Elect Engn State Key Lab Power Syst Beijing 100084 Peoples R China

A variety of distributed generators (DGs) are integrated in distribution system which is usually operated under three-phase unbalanced conditions. The zero and negative sequence impedances of DGs may vary within a large range. In this paper, the convergence problem caused by the zero and negative sequence impedances of DGs in forward/backward sweep three-phase power flow is found through numerical experiments. The reason of this phenomenon is explained and an impedance compensation method is proposed to solve this problem. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： distributed generators Forward/backward sweep power flow Convergence problem

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A Necessary Condition for Power Flow Insolvability in Power Distribution Systems With distributed generators

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IEEE TRANSACTIONS ON POWER SYSTEMS 2017年第2期32卷 1440-1450页

作者： Wang, Zhaoyu Cui, Bai Wang, Jianhui Iowa State Univ Dept Elect & Comp Engn Ames IA 50011 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA Argonne Natl Lab Adv Power Grid Modeling Energy Syst Div Argonne IL 60439 USA

This paper proposes a necessary condition for power flow insolvability in power distribution systems with distributed generators (DGs). We show that the proposed necessary condition indicates the impending singularity of the Jacobian matrix and the onset of voltage instability. We consider different operation modes of DG inverters, e.g., constant-power and constant-current operations, in the proposed method. A new index based on the presented necessary condition is developed to indicate the distance between the current operating point and the power flow solvability boundary. Compared to existing methods, the operating condition-dependent critical loading factor provided by the proposed condition is less conservative and is closer to the actual power flow solution space boundary. The proposed method only requires the present snapshots of voltage phasors to monitor the power flow insolvability and voltage stability. Hence, it is computationally efficient and suitable to be applied to a power distribution system with volatile DG outputs. The accuracy of the proposed necessary condition and the index is validated by simulations on a distribution test system with different DG penetration levels.

关键词： distributed generators power distribution systems power flow analysis power system modeling Wirtinger calculus

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Supply and Demand Control of distributed generators in a Microgrid for New Energy

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ELECTRICAL ENGINEERING IN JAPAN 2009年第4期169卷 1-8页

作者： Shimakage, Toyonari Sumita, Jiro Uchiyama, Noriyuki Kato, Takeyoshi Suzuoki, Yasuo NTT Facilities Inc Tokyo Japan Hitachi Ltd Tokyo Japan Nagoya Univ Dept Elect Engn & Comp Sci Grad Sch Engn Nagoya Aichi 4648601 Japan

We report the operational results of distributed generators (DGs) in a microgrid and present the effects after photovoltaic power generation (PV) systems were incorporated into the microgrid for an electric power system. The microgrid was constructed at the Expo 2005 Aichi site as part of a demonstration promoted by NEDO. A solution is needed for problems in which instability in DGs that utilize natural energy such as solar light and wind force negatively influences existing electric power systems. Consequently, we developed an energy-control system and controlled the output of the DGs to reduce fluctuations at the grid-connection point caused by unstable PV-system output. Our microgrid consisted of DGs such as PV systems, fuel cells, and NaS batteries, and these DGs were controlled by an energy-control system. We tested and then verified the practical effectiveness of installing the microgrid as follows. We found that (1) 99.5% of the power imbalance in supply and demand over a period of 30 min was within a range of +/- 3% under normal operating conditions, (2) the microgrid contributed to load leveling, (3) the energy-control system smoothed the power-flow fluctuations of PV-system output at the grid connection point, and (4) installing microgrids should help reduce additional Load Frequency Control (LFC) capacity in the future. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 1-8, 2009;Published online in Wiley InterScience (***). DOI 10.1002/eej.20872

关键词： microgrid distributed generators fuel cells photovoltaic power generation system NaS batteries 30-minute power balance in supply and demand load leveling load frequency control

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Reliability-constrained Based Optimal Placement and Sizing of Multiple distributed generators in Power Distribution Network Using Cat Swarm Optimization

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ELECTRIC POWER COMPONENTS AND SYSTEMS 2014年第2期42卷 149-164页

作者： Kumar, Deepak Samantaray, S. R. Kamwa, I. Sahoo, N. C. Indian Inst Technol Sch Elect Sci Bhubaneswar 751013 Odisha India HydroQuebec IREQ Power Syst & Math Varennes PQ Canada

This article presents optimal placement and sizing of multiple distributed generators to achieve higher overall system reliability in large-scale primary distribution networks using a novel random search algorithm known as cat swarm optimization. A composite reliability index is used as the objective function in the optimization process. Furthermore, the effect of multiple distributed generator units on power transfer capacity and power loss reduction has been observed. Extensive simulations are carried out based on three practical distribution systems to demonstrate the effectiveness of the proposed method. Further, qualitative comparisons are made with adaptive weight particle swarm optimization, particle swarm optimization with constriction factor, and binary-coded genetic algorithm to show the efficacy of the proposed method for optimal placement and sizing of distributed generators in power distribution networks.

关键词： cat swarm optimization distributed generators distributed generators placement and sizing reliability optimization particle swarm optimization genetic algorithm

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Convergence analysis of implicit Z-bus power flow method for general distribution networks with distributed generators

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IET GENERATION TRANSMISSION & DISTRIBUTION 2016年第2期10卷 412-420页

作者： Zhao, Tian-Qi Chiang, Hsiao-Dong Koyanagi, Kaoru Tianjin Univ Sch Elect Engn & Automat Tianjin Peoples R China Cornell Univ Sch Elect & Comp Engn Ithaca NY USA Waseda Univ Environm Res Inst Tokyo Japan

Implicit Z-bus distribution power flow method may encounter divergence problems when applied to distribution systems with distributed generators modelled as P-V nodes. In this study, analysis of divergence problems associated with the implicit Z-bus method is performed. Physical insights toward the divergence problem are also provided. To this end, the iterative map of the implicit Z-bus method is first derived. Then the fix-point theorem and the non-linear discrete stability theorem are applied to perform convergence/divergence analysis of the implicit Z-bus power flow method. The authors apply the derived analytical results to conduct divergence analysis of the IEEE 13-bus, and a practical 1101-node distribution networks.

关键词： distributed power generation convergence of numerical methods iterative methods power system stability load flow control nonlinear control systems power distribution control convergence analysis implicit Z-bus distribution power flow method general distribution networks distributed generators divergence problems distribution systems P-V nodes iterative map fix-point theorem nonlinear discrete stability theorem IEEE 13-bus 1101-node distribution networks

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Optimal Placement and Sizing of distributed generators in Unbalanced Distribution Systems Using Supervised Big Bang-Big Crunch Method

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IEEE TRANSACTIONS ON POWER SYSTEMS 2015年第2期30卷 911-919页

作者： Othman, M. M. El-Khattam, Walid Hegazy, Yasser G. Abdelaziz, Almoataz Y. Ain Shams Univ Fac Engn Elect Power & Machines Dept Cairo Egypt German Univ Cairo Fac Informat & Engn Technol Cairo Egypt

This paper presents an efficient and fast-converging optimization technique based on a modification of the traditional big bang-big crunch method for optimal placement and sizing of voltage controlled distributed generators. The proposed algorithm deals with the optimization problems incorporating multiple distributed generators for the sake of power as well as energy loss minimization in balanced/unbalanced distribution systems. The proposed algorithm is implemented in MATLAB environment and tested on the 33-bus feeder system and the IEEE 37-node feeder. Validation of the proposed method is done via comparing the results with published results obtained from other competitive methods.

关键词： Big bang-big crunch distributed generators energy loss optimization

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