Research On The Static Stability Of The Distribution Network Considering Plug-in Electric Vehicles With High Penetration And Coordinated Charging

With the increasing acute global energy crisis, oil-based primary energy resourcedepletion and worsening air pollution, governments have come to realize the importanceof energy conservation and emission reduction for the sustainable development of humansociety. Because of the huge oil consumption and greenhouse gas emissions, auto industryhas also been moving up into electric vehicle(EV) which runs upon electricity instead ofoil with zero emissions and low noise. In recent years, EV industry has achieved rapiddevelopment in China with a series of key technical problems solved, and socialacceptance of EV is strong. In the coming decades, EV is bound to have a large-scaledevelopment and application. However, EV load has characteristics of high power andnon-linear, and its charging behavior is of randomness and flexibility. The use of EV willlead to a great increasing of power system load, more severe voltage deviation and morenetwork loss, thus reducing the operational economic efficiency in power systems. A largenumber of EVs charging disorderly will cause a substantial increase in grid load andinfluence the security and stable operation of power system if not controlled. Therefore,it’s necessary to do some research on the impact of large-scale application of EV ondistribution network, so that EV charging behavior is controlled and to become suitablefor future development of EV.This paper briefly introduces the status of the electric vehicle industry and currentresearch on the impact of large-scale application of EV on distribution network toillustrate the importance of the study on EV charging behavior and its effects. Firstly, thestatic load characteristic of EV is analyzed, and a time-space distributed model of EVcharging behavior is put forward. A load calculation model of large number of EVs underuncoordinated charging mode based on the Monte Carlo method which reflects behaviorof private passenger vehicles on five scales: EV type, charging mode, start time ofcharging, place of charging and daily mile is established to evaluate the impact of EV ofhigh penetration on the distribution network. Then, this paper introduces the static voltagestability of power system and its research method, and simulation work of distributionnetwork is carried on based on continuous power flow method, which analyzes the staticvoltage stability margin of the network with EV load or conventional load. On this basis,the impact of gathered charging coefficient on system voltage stability is studied, andcorresponding load-shedding emergency control strategy is figured out. In the end, this paper carries out a research on the coordinated charging strategy of EV based ontime-of-use price, establishes a coordinated charging model, and analyzes the model withuser response or not. Genetic algorithms are used to solve this model. On this basis, theimpact of EVs with different penetration under uncoordinated charging mode andcoordinated charging mode on the distribution network is studied, and a comparison ismade between the results of two kinds of coordinated charging strategies.Results show that charging load of EVs will influence the load curve, node voltage,network loss and static voltage stability of power system. The emergency control strategybased on voltage stability margin can give an effective guarantee for stability of system.And the coordinated charging strategy considering user respond can successfully transferEV load from the peak load period of system base load to off-peak load period, thusimproving the security and economy of system.