Research On Frequency Regulation Of Power System With Electric Vehicles

Along with our country economy scale is becoming larger and larger, the demand for petroleum and other primary energy is becoming bigger and bigger. Primary energy is limited and serious environmental pollution. In order to achieve the goal of energy conservation and low carbon economy, more people put forward to strengthen the development of renewable energy sources such as wind power. Renewable energy output has strong volatility, which is the big challenge for the stable operation of future power system including this kind of energy.With development of electric vehicles, advancement of vehicle-to-grid technology and government’s policy support, the above problem is expected to be solved. Therefore, the research on electric vehicles for frequency regulation in power system, becomes especially important. This paper studies electric vehicles, using vehicle-to-grid technology, charge and discharge reasonably to provide frequency regulation ancillary service for power system. The main research content of this paper is described as follows.The model with charging and discharging static frequency characteristics of electric vehicles is established. Then, the charging and discharging coordinated control strategy of electric vehicles is proposed, to realize role conversion of electric vehicles between distributed generation and controllable load, when load disturbance in power system occurs. To achieve this control strategy, the hierarchical dispatching control method is proposed at the same time, which can realize synchronous charging and discharging of electric vehicles in the related area. On this basis, considering electric vehicle charging and discharging, the load frequency control models of single and two area power systems are established. A simulation study is carried out to demonstrate that electric vehicles for frequency regulation as distributed generation and controllable load, can not only effectively improve the stability of power system frequency, but also remarkably decrease the reserve capacity of traditional frequency regulation units.In addition, based on electric vehicles as the basic attributes of goods, further research on electric vehicles for frequency regulation in power system is studied. Then, the driving rules of electric vehicles are analysed, and the state transition characteristics of electric vehicles, which participate power system frequency regulation, are put forward. Dynamic number change of controllable electric vehicles is effectively simulated, by using the monte carlo stochastic simulation method. After total energy storage model of controllable electric vehicles has been established, in order to prevent electric vehicles from charging and discharging excessively, and considering the randomness problem of users’ habit of driving electric vehicle, power and energy constraints are added in, eventually, lumped controllable electric vehicle equivalent model is formed. By combining this model with traditional two area interconnected power system model, and including factors of wind power and network induced delay, the load frequency control model considering dynamic change of the number of controllable electric vehicles is established. A simulation study is carried out to demonstrate that in two area interconnected power system including wind power and electric vehicles, electric vehicles participate power system frequency regulation, which can not only make stability of power system and dynamic control performance better, but also make power system to be more effective in stabilizing wind power output volatility.