Research On Voltage Characteristics Of Distribution System With Distributed Photovoltaic And Electric Vehicle

In recent years,electric vehicles are deemed a new type of electric equipment which have been scattered in the user side of the distribution system.In the background of electric car ownership continued rapid growth and new energy industry development,there will be a scene that large-scale electric vehicles and distributed photovoltaic connect the distribution system at the same time in the future.It will greatly change the distribution system power supply and demand balance and load flow distribution,also effect the operation of power grid.As one of the main parameters of the power grid,voltage can effectively reflect the safety and stability of power grid.Therefore,it is of great practical significance to study the voltage characteristics of distribution system.The voltage characteristics of distribution system includes voltage distribution characteristics and voltage stability characteristics.These two characteristics are closely related to the load change,which is mainly caused by the electric vehicle load on the assumption that the original loads remain the same,in the daytime.Especially,with highly complex randomness and regional differences,electric vehicle load is influenced by the space-time distribution characteristics of electric vehicle and its connection behaviors.There are few studies on electric vehicle load in the existing literature,moreover,some boundedness exist.It is not scientific accurately to reflect the influence of electric vehicle load on voltage characteristics during the day in these researches.In this paper,the modeling process of electric vehicle load is analyzed first.Then,a new space-time distribution model of electric vehicle is constructed by the combination of trip chain theory and Monte Carlo simulation method,which can accurately reflect the dynamic changes of driving and parking about electric vehicles.It is close to reality and easy to realize and its structure is simple.On the basis of this model,the effect of electric vehicle load on the voltage characteristics of distribution system under different connected behavior is studied.Furthermore,an orderly charge and discharge control strategy of electric vehicles is formulated,which takes into account the user's will and the requirements which is from the grid.Finally,this paper carries out comparison calculation.The results show that the electric vehicle load under this control strategy can suppress the voltage fluctuation of each node,and eliminate the limit of the voltage,and improve the whole system's voltage stability.It is worth noting that,even if the electric vehicle is connected to the distribution system orderly,there still have improvement for the voltage stability.Also,the increase of active power loss becomes a problem that can not be ignored at the same time.In order to solve new problems in the distribution system,this paper constructs a reactive power optimization model considering about increasing stability and reducing losses,which distinguishes the traditional reactive power optimization from the single objective to improve the economic performance of power grid.According to the research ideas of the typical reactive power compensation,a comprehensive reactive power sensitivity index is proposed to select the best reactive compensation node in this paper.And a scientific transformation about the objective functions of reactive power compensation is successful,based on the theory of "Fuzzification-Weight".A modified particle swarm optimization algorithm,which is named Chaos Particle Swarm Optimization(CPSO)algorithm is used to solve reactive power compensation.The results show that the reactive power compensation measures in this paper can effectively control the increase of active power losses,and have a positive and beneficial influence on the voltage characteristics of distribution system with the orderly control strategy of electric vehicles.