Operational Risk Assessment And Control Of Distribution Network With High Penetration Rate Of Distributed Photovoltaic

In the context of fossil energy shortage and intensified environmental pollution,solar energy,as an important renewable energy source,has attracted attention from all over the world for its advantages of cleanness,large reserves and sustainable use.Governments of various countries have taken multiple measures to vigorously develop distributed photovoltaics power generation industry.With the continuous increase of the distributed photovoltaic penetration rate,the distribution network begins to show some new features,such as diversified operation modes,bidirectional power flow,and complicated stability mechanisms,which brings new challenges to the the safe and stable operation of distribution network under the new situation.Therefore,this paper studies the operational risk assessment and preventive control of the distribution network with high penetration rate of distributed photovoltaic.The main work is as follows:Firstly,the basic theory for operational risk assessment of distribution network is introduced,including the risk assessment model,the probabilistic load flow calculation method and the over-limit risk indicator: considering the uncertainty of photovoltaic output and load demand,the photovoltaic probability model and the load probability model are constructed.The principle and algorithm of probabilistic load flow(PLF)calculation are introduced,and the node types of distributed photovoltaics in PLF calculation are studied.The utility function is introduced to represent the severity,on this basis,the operating risk index system is contructed considering both the probability of accidents and the severity of consequences,which includes the node voltage over-limit risk indicator and the branch power flow over-limit risk indicator.Secondly,an operational risk assessment method for distribution network based on improved Quasi-Monte Carlo(QMC)sampling is proposed: the low-discrepancy sequence in QMC method is constructed and then improved by randomizing and linear scrambling,on this basis,the photovoltaic probability model and the load probability model are sampled,and combined with the PLF calculation,the operational risk indicators of the distribution network are obtained.Through simulation analysis of the IEEE-34 node system,the specific impact of distributed photovoltaic with high penetration rate on the operational risk of distribution network is studied.The results show that with the continuous increase of the distributed photovoltaic penetration rate,the voltage over-limit risks of all notes and the power flow over-limit risks of some branches also increase,and the risk value obtained by the proposed method can reflect the real situation more accurately and stably than that by the traditional Monte Carlo(MC)method.Finally,a prevention and control strategy for reduing the operational risk of distribution network based on the demand response(DR)mechanism is proposed: the DR mechanism based on the real-time pricing model and the residential load model is studied.On this basis,a control model is constructed with the goal of maximizing social welfare,while satisfying risk constraints and DR constraints,and the particle swarm ptimization(PSO)algorithm is used to solve this model.Through simulation analysis of the IEEE-34 node system,the operational risk of distribution network with high penetration rate of distributed photovoltaic is controlled.The results show that the constructed risk control model in this paper takes into account the safety and economics of distribution network operation,not only can effectively reduce the node voltage over-limit risk and ensure the safe and reliable operation of the distribution network with high penetration rate distributed photovoltaic,but also can significantly reduce the cost of electricity and power generation and maximize the social welfare.