Coordinated Optimization Of EV Charge-Discharge And Micro Grid Operation

With the increase of energy shortage and environmental pollution problems, countries around the world are actively promoting the development of wind, solar and other green energy, at the same time,also support the development of EV (electric vehicle). However, due to the intermittency and randomness of new energy generation, new energy directly connected to the grid will seriously affect the safety and economic operation of power grid. On the other hand, considering the current structure of primary energy sources in china, if EV is directly charged in grid, the indirect carbon emission is no less than traditional car.Charging for EV with new energy,not only reduce the indirect carbon emissions of EV, but also realize the local consumption of new energy.Therefore, it is necessary to study the charging/discharging of electric vehicle and the operation of micro grid.Firstly, in this paper,the load characteristics of EV are analyzed from three aspects:the EV type, running quality, and energy supplement. Based on the statistical results of annual household vehicle driving pattern in 2009 released by US DOT (Department of Transportation), and the charging characteristic of EV, a load model of EV charging is established. Then response degree of EV are divided into three levels in accordance with the degree of EV meeting dispatching of power grid. From the adjustable time period and the adjustable capacity, analyze the response capability of the EV, and determine the power range of EV in each period of time.Then, establish the output model of micro-sources, and distribution model of wind speed and light intensity in short period. By analyzing error distribution of output prediction on wind power systems and photovoltaic power generation systems,determine the error distribution model of prediction, and solve the parameters of the model by using MMLE (Maximum Likelihood Estimation), based on charging load model of EV and micro-grid model, three evaluation indexes are proposed. By comparing the three indexes before and after the access of EV, the effects of EV access to micro grid in the way of disorder charging is quantitatively analyzed.Finally, aiming at maximizing the utilization of new energy in micro grid, this paper presents a new two-stage dispatching mode considering EV responsiveness. In the first stage, based on output prediction of micro-grid energy, EV responsiveness level and prediction of charging demand,day-ahead cluster dispatching model is established. In the second stage, in order to minimize the deviation of the result of the cluster scheduling,real-time single car dispatching model considering prediction error of new energy, EV responsiveness level and capacity is established. By using the three evaluation indexes to quantitatively analyze the proposed model in improving new energy efficiency and micro-grid average rate of power supply, in reducing the electricity purchase of micro-grid, lowering the cost of micro grid, and increasing the on-grid new energy, as well as relieving the intermittent and variability of micro-grid energy which is bad to power grid.