Reliability Evaluation Of DC Distribution Network With Distributed Generators

With the deterioration of fossil energy and environment problem,the continuous improvement of penetration of distributed and renewable energy(wind power,PV and so on)in the distribution network,compared with traditional AC distribution network,DC distribution network is convenient for distributed generators(DG),and can effectively use of renewable energy.Because of strong randomness and intermittent of wind power,photovoltaic,these distributed power access will have a greater impact on DC distribution network reliability.Therefore,the study of power output modeling of DG in DC power distribution network and reliability evaluation method of DC power distribution network containing DG is of great significance for the planning,construction and operation of DC power distribution network,has high theoretical value and practical significance.Based on a demonstrative project of DC power distribution network in industrial park in Shenzhen supported by Guangdong Leading Talents Introduction Special Funds,considering the influence of the redundancy of component based on power electronic devices and the randomness of distributed power supply,this article was focused on the modeling and evaluation of island DC system and DC power distribution network containing DG.In order to get more accurate parameters of DC critical equipment,the key component's reliability model which considering the redundancy of power electronic devices including key equipment in power system was established,based on the topology and operation principle of themselves;Based on the modeling,the reliability of the key equipment in the demonstration project of DC distribution network was calculated and provided data support for subsequent chapters.Results showed that power electronic devices had great influence on the reliability parameters of key equipment,component based on power electronic devices redundancy reduced the failure rate of the key components and improved their reliability.In order to establish a more accurate model of distributed power supply of DC distribution network,according to the structure characteristics of DC distribution network,improving the existing DG topology,the DG topology for DC distribution network was obtained.Based on hierarchical simplification network of DG,considering the influence of uncertainty of wind speed,illumination intensity and DG component failure,Sequential Monte Carlo model for DG output was built.Two types index(energy and time)was defined to measure the influence of wind speed,illumination intensity uncertainty and component failure on DG output performance.Then the output performance of DG under different scenery configurations was evaluated.Numerical example showed that the DG output model can accurately evaluate the output performance of DG;Output performance changed by different configuration of the wind/PV;Reasonable configuration of the wind/PV can effectively improve the output performance of DG.In order to evaluate the influence of the uncertainty of distributed power supply on the reliability of the isolated islands in the DC distribution network,based on the aforementioned reliability model of key equipment and output model of distributed power,the energy storage operation strategy,the optimal cutting load strategy in isolated islands and sequential load model were combined.Considering the influence of the uncertainty of distributed power supply on the reliability of isolated island operation area,the reliability index of the traditional system was improved.Sequential Monte Carlo reliability evaluation model for the isolated island operation area of DC distribution network was built.The reliability of the "isolated island" in the DC distribution network demonstration project was evaluated.The influence of DG output's uncertainty,configuration of the wind/PV and load level on the reliability of the isolated island in the DC distribution network was analyzed.Results showed that the uncertainty of DG output had a great influence on the reliability of the isolated island in the DC distribution network,solving the problem of wind power and photovoltaic output of the volatility to ensure the reliability of the island operation area.With the increase of PV capacity ratio,the reliability of isolated island operating area in DC distribution network increased;With the increase of load level,The reliability of the "isolated island" operating area in DC distribution network reduced.Considering isolated island operation,the energy storage operation strategy,fault and load shedding strategy and so on,based on the key equipment reliability model and distributed power output model,sequential Monte Carlo evaluation model for distribution network was built.The existing indicators was improved in order to evaluate the influence of distributed generation on the reliability of DC distribution network.A demonstrative project of DC power distribution network in industrial park in Shenzhen as an example,the influence of DG interconnection,DG rated capacity,DG equivalent output model and component redundancy on the reliability of DC power distribution network was evaluated.Numerical example showed that connecting the DG to a DC distribution network can effectively improve the reliability of isolated load point and DC distribution network,the improvement effect was also related to the rated capacity of DG and the output model of DG;In addition,the redundant design of the DAB in the DC transformer and the redundant design of the solid state switch sub module of the DC circuit breaker can reduce the average failure rate of each load point,improve system reliability.