# PV-Powered Charging Station for Electric Vehicles: Power Management with Integrated V2G
###### Abstract
The former has high construction costs, while the latter has the problem of difficult control. Therefore, the V2G based on a direct current (DC) microgrid control mode is proposed, which makes EVs connect to the public grid through a DC microgrid, moreover, it effectively integrates renewable energy, whilst meanwhile saving the cost of buying electricity from the public grid. V2G based on the microgrid is used for multi-objective optimization coordination between EVs and the public grid to minimize grid load fluctuation, maximize renewable energy utilization, and maximize the benefits for the EV users [25]. The paper [26] proposed a centralized model to co-optimize the transformer loss-of-life with benefits for EV users on charging/discharging management. As an optimal energy cost solution, cyber insurance was introduced to guarantee the best price for charging/discharging, which is effective not only in dealing with cyber risks but also in maximizing revenue for EV users [10]. The paper [27] develops a model predictive control-based approach to address joint EV charging scheduling and power control to minimize both EV charging cost and energy generation cost in meeting both residence and EV power demands. A DC microgrid with integrated V2G has also been examined in other papers [28; 29]. The paper [28] proposes an optimal day-ahead operation planning procedure that aims to minimize microgrid operation daily costs, according to suitable load demand and source availability forecast without involving MATLAB/SIMULINK modeling. The review paper [29] focuses on the charging system components, architecture, operational modes, and control, including the interaction between the PV sources, public grid, energy storage unit, and power electronics, however, it does not take into account the management of multiple EVs. In addition, V2G was characterized as a comparatively advantageous means of peak load shaving [10]. The paper [24] proposes an optimal logical control algorithm based on V2G to reduce the average charging cost of EVs, which is dedicated to the French energy billing system within the peak/base hour's contract. The algorithm can minimize the EV charging cost and maximize energy selling by using daily energy price profiles, considering constraints and disruptions: EV arrival/departure times, and the desired state of charge (\(soc_{EV}\)) for the next use. However, this algorithm has not yet involved a PV-powered charging station and research in the microgrid field. In a V2G system, the EV charging station can obtain the optimal charging/discharging start time by reading the EV's arrival time, departure time, initial state of charge namely \(SOC_{EV\_in}\), and the state of charge limit at the time of departure, namely \(SOC_{EV\_final\_lim}\). Based on the above, this paper proposes an EV charging station management with integrated V2G, in which the optimal charging/discharging start time for EVs can be achieved to perform the purpose of peak and valley filling through a dynamic searching peak and valley algorithm (SPVA). Compared with the power limit of the public grid in the \"valley\" period, the power limit of the public grid absorbed from the microgrid is larger, while the power limit of the public grid released to the microgrid is smaller during the \"peak\" period. Therefore, when EVs connect to discharge, the charging station will select a time point near the \"peak\" periods for EVs; when EVs connect to charge, the charging station will choose a time point far away from the \"peak\" periods, which can not only relieve the pressure on the public grid but also reduce unnecessary charging costs. In order to protect the stability of the public grid, the energy injected into the public grid needs to be limited, namely the self-protection mechanism of the public grid. To better ensure the stability of the public grid, the power limit of the power grid is set to different values according to the \"peak\" periods and \"valley\" periods.