Influence Of Large-scale Application Of Electric Vehicles On Reliability Of Power System With Wind Farms

In recent years,under the background of the pressure of fossil energy reserves and environmental pollution,the scale of wind power generation has becoming more and more large.Due to the volatility and intermittent nature of wind power,it has exerted great pressure on the stable operation of the power system.On the other hand,with the rapid popularization and application of electric vehicles,its influence on the power system cannot be ignored.The introduction and application of V2G(vehicle to grid)technology provide new ideas for solving the above problems.V2G technology allows power batteries in electric vehicles to feed power back into the grid.This paper analyze the feasibility of using V2G technology to improve the reliability of power systems under the conditions of large-scale electric vehicles and wind power.Firstly,the characteristics of wind power generation was analyzed,and the short-term wind speed was predicted by using the time series method based on auto-regressive moving average model.The comparison between the predicted results and the measured results shows that the time series method has better timing and accuracy in the short-term wind speed prediction and with the increase of the prediction time,the accuracy has an obvious decline.The forecast wind speed and the actual wind speed are fitted with the two-parameter Weibull distribution model,and the results show that the distribution of predicted wind speeds is similar to the actual situation,which also reflects the accuracy of the short-term wind speed forecasting by the time series method.Then the Monte Carlo simulation method of power system's reliability evaluation was introduced,and the reliability indexes such as loss of load probability and expected demand not supplied were given.The influence of wind power on power system reliability under different installed capacity was simulated.The results show that with the increase of capacity,the system reliability increase gradually slows down.By comparing the influence of the conventional unit with the same capacity on the reliability of power system,we can see that the wind power 's improvement effect on system reliability is significantly weaker than that of conventional units,which also reflects the limitation of volatility and intermittency to the use of wind power.After that,this paper analyzed the influence of traditional electric vehicles on power system reliability.Firstly,by analyzing the factors affecting the charging load of the traditional electric vehicle and the relevant statistical rules,the stochastic charging load of the traditional electric vehicle was modeled,and the load curve of the electric vehicle under the random charging mode was obtained.Then,by increasing the proportion of electric vehicles,we further analyzed the impact of electric vehicles on the power system.The results show that with the increase of the proportion,the reliability of power system gradually decreases,and the decline of reliability is more obvious.It can be seen that with the increasing use of electric vehicles,the future power system will face great potential impact.In the end,the concept of virtual combined load was used to consider the volatility factors in the wind power system.With the help of V2G technology,an optimization model of charge and discharge control strategy for electric vehicles was proposed,which was used to smooth the virtual load fluctuation and improve the reliability of the power system.The particle swarm algorithm that adds a decreasing inertia weight factor was used to solve the model.By solving the model,the specific charging and discharging strategies of electric vehicles were obtained.Compared with the changes before and after the proposed strategy,it can be found that the standard deviation and peak-valley difference of virtual combined load have obvious decline,which indicates that the volatility of the virtual load has been effectively reduced,and the reliability level of the power system has also been effectively improved.As the proportion of electric vehicles was increased from 12%to 24%,the standard deviation and peak-valley difference of the virtual combined load decreased more significantly,and the reliability level increased significantly.This shows that with the further popularization of V2G electric vehicles in the future,the charging and discharging strategy proposed will have a more significant effect on the reliability of the power system,which indicates the importance of electric vehicles in promoting the acceptance of renewable energy in the power system.