The Optimal Charging Strategy Of Electrical Vehicle For Minimizing Micro-grid Load Variance

With the rapid and continuous growth of Chinese economy, energy security, climate change, environmental capacity and other issues increasingly become the focus of the whole society. Promoting the comprehensive transformation of energy production and consumption will be the fundamental way out to the sustainable development of economic society as well as the realization of the great rejuvenation of the Chinese nation. Promoting the application of electric vehicles to replace traditional fuel vehicles is a major move for our country to achieve energy transformation. It can be anticipated that with the strong support and guidance of national science and technology as well as the industrial policy, the production and sales of electric vehicles will embrace an explosive growth in the next five to ten years. With the popularity of electric vehicles in the future, a very serious problem will soon surface: the concentrated charging of large-scale electric vehicle will bring a catastrophic damage to the existing power grid.At the end of 20 th century, the researchers have put forward the concept of the energy interaction between electric vehicles and grid to guide conventional electric vehicles to charge in the trough period of load curve, and fed into the grid at peak period, in order to alleviate the impact of the large scaled access of electric vehicles on the existing power grid. As a means of transport, however, the basic use of electric vehicles is to meet people’s daily travel needs. Electric vehicle charging is the fundamental power source. Because there is a big randomness of the charging time and space of electric cars, and the number of electric vehicles of China in the future will be large, how to develop a reasonable charge and discharge strategies to minimize the power grid loss to meet a large number of electric vehicle charging needs, is the main research direction of this paper. The main research work is as follows:(1) The introduction of the charging way of the electric cars on the basis of their charging power. The explanation that disorderly charging will raise the problems such as pushing the peak load up, dropping the voltage and increasing line loss. The analysis that electric vehicle in V2 G technology under the existing power grid can play a role in loading shifting, and help stabilize intermittency and volatility of renewable energy, such as wind, solar, thus increasing the power grid’s ability to seamless consumption.(2) Details of the framework of V2 G implementation, on the base of the building of V2 G systems framework, electric vehicle charging strategies were modeled, established the mathematical model constraints aimed at a micro-grid load variance minimum and to satisfy power supply and the demand of electric vehicles. Then the model is analyzed, explaining the conditions of use of the model as well as deficiencies and improvement direction.(3) The selection of investigation period as well as its discretization has been described. The classified constraint of the possible cross-cycle of electric vehicle, based on which energy model of vehicle scheduling random arrival is built.(4) The data of electric vehicles was simulated on the research of a certain workspace charging station, which was optimized based on simulated data of the workspace. Through the analysis of simulation results, it illustrated that this model can effectively improve the quality of power grid.