Harmonic Compensation Strategy for Extending the Operating Range of Cascaded H-Bridge PV Inverter

For single-phase cascaded H-bridge (CHB) photovoltaic (PV) inverters, all the PV modules are able to operate at the maximum power point, which is beneficial to energy harvesting. However, due to the stochastically variable irradiance level and ambient temperature, the unbalanced output powers among PV modules may cause the overmodulation of the H-bridges with higher power, ultimately resulting in a distorted grid current. In this paper, a novel harmonic compensation strategy is proposed. Compared to the existing methods, it can not only ensure that CHB inverter operates at unity power factor with small dc-bus voltage ripple but also keep the total harmonic distortion of grid current in acceptable range under some heavy power unbalance conditions, so it has a good overall performance. Simulation and experimental results validate the effectiveness and feasibility of the proposed method.