Model predictive direct power control strategy for leakage current suppression on a grid‐connected three‐level inverter

Abstract

AbstractThe nonisolated grid‐connected photovoltaic inverter system suffers from the problem of leakage current. Therefore, a leakage current suppression control strategy based on the model predictive direct power control is proposed for the three‐level four‐leg grid‐connected inverter. At first, the system model is established to analyze the factors that affect the leakage current and the potential of the neutral point. Second, the first three legs, inverting part, use model predictive direct power control, and the fourth leg of the inverter is used to maintain a constant common‐mode voltage to achieve the suppression of the leakage current. The fourth leg is indirectly controlled by the switch state of the first three legs; thus, the number of optimization times is reduced. Finally, by simulation, the leakage current is compared and analyzed with the three‐level three‐leg inverter under conditions with different parasitic capacitance values. The results show that the proposed strategy suppresses the leakage current by more than 60% without affecting the neutral point potential and has a fast optimization speed.