Operation Optimization Of AC/Dc Hybrid Microgrid With Electric Vehicles

Environmental and energy problem have led to the rapid development of renewable energy technologies such as wind power and photovoltaic,as well as new energy technologies such as electric vehicles,which are alternatives to fuel cars,under the national policies and people’s gradually awakening green environmental awareness.As the installed capacity of renewable energy and the size of electric vehicles(EV)continue to expand,the operational problems of the system become more complex as the number of participants increases.In this paper,the impact of EV access to power system is analyzed.Considering the uncertainties in the system,a robust optimization model of the AC/DC hybrid microgrid with EV as the research object is established.Based on the game theory,EV was taken as the market transaction subject,and a bargaining model of internal charge and discharge price between EV and microgrid operators is established.The main work and conclusions are summarized as follows:(1)Based on the travel habits of EV users,the disordered charging and ordered charging and discharging load models of EV are established.Then,for example analysis,EV is connected to IEEE 33-node system.The influence of EV to power flow of the connected system is analyzed from the scale and location of EV.Based on the two load models,the disordered charging and ordered charge-discharge load curves under different vehicle numbers are obtained,and the influence of different EV network entry behaviors on system load is analyzed.Simulation analysis shows that,the increasing EV load will increase the network loss of the system,reduce the voltage and affect the stability of the system operation.In addition,different access nodes have different influences on the connected system,so the access location should be considered during planning.At the same time,the mobile energy storage characteristics of EV’s power battery can be reasonably utilized to reduce the system load and improve the operating economy.However,with the increasing number of EV participating in charge and discharge operation,the centralized transfer of charging load and discharge power may cause new peak-valley difference in the optimized load.(2)The EV is connected to the AC/DC hybrid microgrid for charge and discharge scheduling.Aiming at the uncertainty of renewable energy and load demand in the system,a two-stage robust optimization model is built.The uncertainty set is used to describe the uncertainty in the model,and the conservatism is adjusted by the uncertain budget.Combined with the operational constraints of each unit,the model was sorted into a matrix form,and the model was decomposed and transformed into a form that could be directly solved by strong duality theory and Big-M method,and the column constraint generation algorithm was used for iterative solving.The influence of EV access to microgrid in economy and system energy storage utilization is analyzed with a numerical example.Based on the numerical example,the optimal number of EV in this scenario is obtained,and the robustness and economy of the proposed model are discussed.The results show that the scheme obtained from the robust optimization model can better cope with the fluctuation of the system uncertainty factors.Combined with the real-time scheduling stage,the economy of the model is also effectively verified,which indicates the correctness of the established model.(3)Based on the background of the reformation of power market,taking EV as the stakeholder to participate in the pricing of charge and discharge electricity,and considering the uncertainty of the output and load of the microgrid in the system,a robust non-cooperative game pricing model of charge and discharge electricity price between EV and the microgrid is established.Particle Swarm Optimization(PSO)was used to solve the model,and the operation and price of the microgrid and EV are analyzed under the equilibrium solution of the model.The simulation results show that the operation cost of the microgrid system is further optimized under the bargaining model,and the benefits of EV users are also satisfied too.The scheme is more comprehensive and the operating cost of the system is lower,which verifies the correctness of the model.