| Electric vehicles(EV)have great advantages in environmental protection,energy conservation and emission reduction,and become on of the important ways to alleviate the energy crisis.EV charging load has great uncertainty in both time and space.Once EV is cennected to the distribution network with a large scale,it will have a certain impact on the safe and stable operation of the distribution network,and even lead to voltage collapse of the distribution network.With the rapid increase of electric vehicle ownership,it is urgent to study the temporal and spatial distribution characteristics of charging load and the access ability ofelectric vehicles.The EV charging load has the characteristics of randomness,intermittency and nonlinearity.The temporal and spatial distribution characteristies of EV charging load are not only related to the parameters of EV itself,but also closely related to the behavior characteristics of the drivers.With the analysis of EV performance parmeters and driver beh avior characteristics,the EV charging load model is established based on Markov Chain and Monte Carlo stochastic theory.The temporal and spatial distribution regulation of charging loads in the three different types EV:bus,taxi and private.The influence of electric vehicle access on the daily load curve of distribution network is analyzed.The harmonic characteristics of EV charger during grid-connected charging are analyzed from four aspects:voltage level of charging station,power supply distance,charging power and charger type.The distribution characteristics of the super-harmonics injected into the power grid by PWM charger at high frequency are analyzed.Based on the continuous power flow algorithm,the influence of certain scale EV aoccess on static voltage stability margin and static voltage stability limit of distribution network is analyzed.The IEEE33 node typical distribution network is taken as an ex ample for verification.Based on the harmonic index and the static voltage stability margin index,the calculation model of the accessible quantity of electric vehicles is given.The maximum access quantity of EVs satisfied the requirement of national harmonic standard is obtained.Three grid-connection scenarios of EVs including distributed power supply and base load growth are set.The static voltage stability margin of the distribution network in time dimension under three scenarios is obtained.The maximum quantity of accessible EVs under three scenarios was assessed.The change of the static voltage stability limit in time dimension at 33 nodes of distribution network under three scenarios is calculated.The analysis results show that the base load growth of distribution network has little influence on the static voltage stability margin of distribution network,and the static voltage stability limit of access node can be improved obviously when distributed generation is connected to distribution network. |
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