Abstract:
Affected by partial shading, self damage and other factors, the transmission power between H-bridge modules of single-phase cascaded H-bridge photovoltaic grid-connected inverter system is unbalanced. As a result, the H-bridge module with high transmission power is prone to overmodulation, which leads to the deterioration of grid current and even affects the stable operation of the system. Therefore, an optimized third harmonic compensation strategy is proposed, through the accurate calculation of the third harmonic compensated by the overmodulation module, the amplitude of their modulation wave is 1. At the same time, combined with the optimal distribution of inverse third harmonic among the normal modules, the overmodulation of each H-bridge module is avoided to the maximum extent. The simulation model is built in Matlab/Simulink, and the simulation results of the proposed control strategy are compared with the conventional third harmonic compensation strategy and hybrid modulation strategy, and the excellent performance of the proposed control strategy is verified.