| The increasing complexity of the distribution system, and frequent natural disasters, make system failure inevitable. With the development of distributed generation(DG) technologies, taking full advantage of its power generation capacity in the service restoration scheme is an effective means to improve system reliability. This paper focuses on the service restoration problem with DG, and the following work is done:(1) Several basic issues are discussed on service restoration of distribution systems with DG, and a corresponding single-period service restoration model is established.(2) As large number of infeasible solutions which violate the "radial distribution network constraints" will be generated during some optimization algorithms, this paper proposes an effective method on radial network generation based on the fundamental loop matrix. By opening and combining loops dynamically, this method avoids the generation of infeasible solutions, and improves calculation speed.(3) As conducting "main network reconfiguration" and "island generation" separately will lead to the optimization unsynchronized, this paper constructs an "extended network" with "virtual branches" connecting each DG and the substation, so that the two processes can be unified into a single reconfiguration problem on the "extended network", which avoids mutual interference of the above two processes, making the restoration scheme more satisfying.(4) As restoration methods of previous study cannot effectively coordinate two ways of load shedding, namely "curtailing the controllable loads" and "disconnecting circuit breaker and generating a blackout area", this paper gives mapping rules from the "load status" to the final load shedding program, so as to balance the selectivity and simplicity of the restoration scheme.Example shows that the proposed algorithm is simple and effective, and is able to take flexible measures according to different fault severity and operating conditions, leading to a satisfactory result. |
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