Research On Urban Power Grid Fault Analysis And Power Supply Recovery Strategy Considering Electric Vehicle Discharge Behavior

Compared with traditional fossil energy vehicles,electric vehicles have the advantages of low-carbon,environmental protection,clean and energy saving,and can actively respond to and cooperate with the national sustainable development policy.In recent years,they have been vigorously developed.It is estimated that by 2030,the number of electric vehicles will account for 50% of the total number of vehicles.When the electric vehicle with source load duality is connected to the urban power grid,the discharged electric vehicle will significantly change the source load structure and power flow characteristics of the urban power grid,and then change the fault characteristics of the urban power grid and enhance the security risks.Therefore,considering the coupling relationship between electric vehicles and urban power grid,analyzing the impact of electric vehicle discharge behavior on urban power grid,and studying the fault analysis method and power supply recovery strategy of Urban Power Grid Considering electric vehicle discharge behavior are of great significance for the safe and stable operation of urban power grid in the future.This paper mainly includes the following contents:1)A fault analysis method of Urban Power Grid Considering the discharge behavior of electric vehicles is proposed.Firstly,the influence mechanism of electric vehicle discharge behavior on urban power grid fault current is discussed.Secondly,the vehicle transfer matrix based on Markov chain is used to describe the travel behavior of all electric vehicles in a certain area.Then,Monte Carlo method is used to study the area and charging and discharging state of all electric vehicles at each time of the day.The research object is transformed from electric vehicle to charging pile,and the electric vehicle discharging to the urban power grid is regarded as the power source with variable output.Thus,the urban power grid containing a large number of electric vehicles is transformed into an active distribution network,and the active distribution network with variable output is established Source model.Finally,taking three-phase short-circuit fault as an example,referring to the fault analysis method of active distribution network,the fault current of Urban Power Grid Considering the discharge behavior of electric vehicles is analyzed,and the fault current of each branch of urban power grid under the influence of electric vehicle discharge is obtained.2)On the basis of fault analysis,the improvement scheme of urban power grid protection considering the discharge behavior of electric vehicles is formulated.Firstly,according to the grid connection position of the electric vehicle connected to the grid through the centralized charging pile and its relative position with the fault point,the protection action schemes under various fault scenarios are analyzed.3)In the case of protection action,in order to restore the power loss load after the fault is cut off,the power supply restoration strategy of urban power grid based on V2 G technology is studied.Firstly,on the basis of studying the discharge behavior of electric vehicles,the discharged electric vehicles are added to the power supply restoration of urban power grid as the power supply restoration resources,and the load loss evaluation system is proposed,so that the limited electric vehicle resources can act on the load with high importance and large power loss.Then,in the specific distribution of power supply,in order to minimize the overall power loss of load,the optimization model of power supply restoration distribution scheme is established,which is solved by genetic algorithm and improved whale algorithm.Finally,the simulation results show that the research method can make full use of electric vehicle resources and the recovery strategy is feasible.