Security And Reliability Evaluation Of Distribution System With Distributed PV

With the continuous expansion of photovoltaic(PV) power generation scale, safe and reliable operation and protection control of the distribution network have been adversely affected, in particular, the influences that fluctuation of PV output brings to power quality and grid connection cannot be neglected. It restricts the PV power capacity and scale and brings new challenges to the safe operation of distribution system. It is therefore necessary to evaluate the security and reliability of system after interconnecting PV to the power system to make sure that PV system access to distribution network correctly and make full use of its advantages.The comprehensive evaluation approaches to evaluate security and reliability of distribution network with PV are proposed, respectively. In the first place, the impacts that PV brings to power supply quality, capacity and grid structure are analyzed. The security index system is constructed from voltage security, system losses, margin, vulnerability, system balance degree and other aspects. The fluctuating nature of PV and the pertinence among PV output, distribution network and loads is discussed, then the ways to reduce the impacts caused by PV fluctuation are analyzed.Secondly, in order to reflect the PV output fluctuation and loads uncertainty, a dynamic evaluation approach about distribution network security with PV is established based on fuzzy matter-element method considering the time factor which can conquer one-sidedness of static evaluation approach and make the results more exact. Then the model of a 10KV level distribution network system is established on OpenDSS platform by selecting typical meteorological data and loads data to simulate the uncertainty of PV output. In addition, the opinions of PV accessed are proposed by dynamic evaluation results under different distributed PV capacity, interconnection points, combination methods and different weather, it’s of great significance for reasonable planning and operation of distribution network with PV.Finally, the reliability index system is established by analytic hierarchy process(AHP) approach based on engineering statistical algorithm on reliability research, includes general reliability, economic reliability of distribution network and equipment characteristic. Considering the island effect, some indicators have been amended after analyzing the influences on reliability indicators, evaluation methods, models and economy caused by distributed PV. After formulating marking criterion of foundational indicators, the example by power cut data of a 10KV distribution network has been analyzed.