Optimal Control Strategy for Frequency Response of V2G Grid-Connected Inverter Considering SOC Characteristics

Abstract

New energy-vehicle charging and discharging units in vehicle to grid (V2G) application scenarios experience long and large transient fluctuations in power and frequency at their power injection points. Furthermore, the power matching degree is low, which has a serious impact on the V2G support performance. This paper proposes a two-step model prediction-virtual synchronous machine (MPC-VSG) control strategy that considers the SOC of the charging and discharging unit. First, the VSG equivalent model of the V2G grid-connected inverter is established, and the power weight coefficients of the charging and discharging unit SOC participating in frequency regulation are obtained by analyzing its characteristics. Second, the power change prediction value is obtained from the VSG model, and the two-step prediction of the reference frequency is performed to reduce the error of the reference value remaining unchanged at the instant of sudden power change. Minimizing the sum of squares of real-time output power deviations and frequency fluctuations as a cost function to compensate for the optimal active losses and suppress the frequency transient fluctuations. Finally, simulation analysis is carried out under the working conditions of island mode operation, V2G grid-connected operation, and wind power multi-energy complementary operation, and an experimental verification of the inverter part is carried out to verify the effectiveness and superiority of the proposed control strategy.