Research On Reliability Of Distribution Systems With DG Considering EV

With the increasingly prominent problems of energy shortage and ecological environment,the use of clean renewable energy for power generation in the power system and the use of electric vehicles to replace traditional fuel vehicles have become effective measures to solve the current energy and environmental crisis.Distributed clean power supply and electric vehicle access to the network will change the structure and operation mode of the traditional distribution systems and the reliability of the system.Moreover,the intermittent,random and fluctuating output of distributed power supply will be superimposed with the disordered charging load of electric vehicle,which puts forward higher requirements for the distribution systems capacity.It brings great challenges to the operation and regulation of distribution systems.After a large number of electric vehicles are connected to the distribution systems,because of the energy storage characteristics of batteries,the charging load of electric vehicles is controllable.Using certain scheduling strategies,the charging and discharging loads can be fully utilized to improve the system reliability,optimize the load curve and increase the ability of the system to absorb renewable energy.Firstly,this paper explains the evaluation index and method in the traditional reliability evaluation of distribution systems;summarizes the influence of different grid-connected,access and operation modes of distributed generation on the reliability of distribution systems;explains the output model and reliability evaluation model of wind power and photovoltaic power generation;sets up three different scenarios,and compares and analyses the distribution using Monte Carlo simulation method.The impact on the reliability of distribution systems.It is concluded that in the planning of distribution systems,factors such as access power,access capacity and failure rate of distributed generation should be taken into account to improve the reliability of the system more economically and effectively.Taking private fuel vehicles as the research object,according to the division of working days and weekends,the travel characteristics such as travel mileage,travel time and travel frequency are analyzed,and the distribution function is fitted.Based on this rule,an EV travel behavior model is established based on the travel chain.Based on the trip chain model of EV,the charging and discharging constraints of EV are analyzed,and the calculation method of SOC limit of EV is obtained.Based on the test system of IEEE RBTS-6 F4,the load of the system is divided into three categories according to the measured load data:residential load,commercial load and office load,and three micro grids are set up to operate in an isolated network.According to different scenarios,the effects of electric vehicle and wind power on distribution systems reliability and load curve are studied.It is concluded that the peak value of disorderly charging load of EV will overlap with the peak value of system load,which will deteriorate the operating environment of the system.After a large number of EVs are connected to the distribution systems,certain means should be taken to schedule their orderly charging.Under the cooperation of EV2G technology and wind power,the reliability index of the system will be improved to a certain extent.Considering the SOC limit and the number of charging-discharging state flips of EV,the priority index of EV dispatching is established,and the EV dispatching is graded according to the index.Based on the dispatching classification,the orderly charging and discharging control method of EV is proposed by using particle swarm optimization algorithm,according to the normal and fault states of the system.According to the historical load value of the system and the expected value of control,the priority index of EV dispatching is established.The correlation coefficient calculation function is proposed to change the smoothness of the expected value by adjusting the target value parameters.Using the test system,the effects of orderly charging and discharging on system reliability and load curve under different strategies are analyzed.Finally,it is concluded that the control method proposed in this paper can effectively improve the reliability of the system,and reduce the peak load of the system and increase the valley load of the system.