Optimal Load Dispatch When Connected To Electric Vehicles In DC Microgrid

Electric vehicles and renewable energy are two emerging industries in China,which will play a crucial role in the future development of the country.Renewable energy is easily affected by external natural environment factors,resulting in strong randomness and difficult to improve the development speed.The advantage of the DC microgrid system is that not only does not need to consider the impact of reactive power and frequency changes on the operation of the system,but also through the coordinated control of renewable energy and energy storage units connected to the DC microgrid system,it can promote the entire DC microgrid to maintain operational balance,and achieve the purpose of ensuring the stability and reliability of the entire DC microgrid.At the same time,large-scale electric vehicles and various distributed power sources are connected to the DC micro grid to form a centralized and unified coordinated control,which can further promote the effective use of renewable energy and continuously reduce the cost of photovoltaic and wind power.Considering that a large number of electric vehicles are likely to be connected to the power grid at the same time during the peak load stage,it will lead to an increase in the peak-to-valley difference of the power system,which will further cause the power grid bus voltage to fall,the power quality to reduce and other problems that endanger the safe operation of the microgrid.Therefore,it is urgent to carry out research on the load optimization scheduling of DC microgrid considering the access of electric vehicles,analyze the relevant problems involved in the load optimization and dispatch of DC microgrids with wind and photovoltaic storage and combustion under the access of electric vehicles,provide strategic support for the optimal charging pile of electric vehicles,realize peak shaving and valley filling of electric energy,and provide certain support for promoting the development of the national energy Internet layout.In this paper,the characteristics of the DC microgrid system when connected to the electric vehicle were analyzed by simulation means,including the characteristics of the wind turbine power generation unit,the photovoltaic power generation unit,the diesel power generation unit and the micro gas turbine power generation unit,as well as the power generation cost of each power generation unit.At the same time,a method for improving the efficiency of single-phase LLC resonant converter was proposed,and the converter inductance ratio,characteristic impedance and transformer turn ratio were simulated and optimized,and bilateral soft switching was realized in the high output voltage area,and the conduction loss could be minimized by optimizing the resonance parameters.In order to reduce the total cost of DC microgrid and users,improved the stability and scheduling economy of DC microgrid,this paper simulated and modelled the uncertainty of electric vehicles connected to the power grid by Monte Carlo method,and proposed a multi-objective load optimization scheduling model for electric vehicles randomly connected to DC microgrids,which analyzed the operating costs,environmental pollution control costs and load variance of electric vehicles from three aspects.Subsequently,the objective function and the constraint function in the scheduling model were discussed in detail,and the improved particle swarm algorithm was used to efficiently solve the model by improving the traditional particle swarm calculation.The results showed that in the orderly charge and discharge mode,the load of the DC microgrid was transferred from the historical high price period of disorderly charge and discharge of electric vehicles to the low-price period,which reduced the total cost of operation of the DC microgrid and improve the operational stability of the DC microgrid.By managing the power output of wind power generation units,photovoltaic power generation units,diesel generator units,and micro-gas turbine units,the total operating cost of DC microgrids could be further reduced.Since the cost weight factor was an important measure of the total cost of grid operation and the stability of the power grid operation,the manager could use this cost weight factor to control the cost preference and degree of the stability of the DC microgrid and the comprehensive economy of grid dispatching.Effectively,the dispatching mode reduced the total cost of users and improved the stability of DC microgrids in different charge and discharge modes.