Combining Common DC-Link Utilization and Zero-Sequence Injection for Power Balancing in Hybrid Cascaded H-Bridge PV Inverters

Cascaded H-bridge converter (CHB) is from leading configurations for grid-connected photovoltaic (PV) systems with a distributed arrangement of PV panels. However, phase power imbalance is an intrinsic challenge for this architecture, which results in grid current distortion and dc-link voltage deviation. This article proposes two novel power-balancing methods for a hybrid-CHB PV inverter, which consists of the CHB converter in series with a three-phase (TP) module. In the first method, the existing common dc-link in the hybrid-CHB configuration is employed to evenly redistribute the generated PV power among the three phases. The second method combines the redistribution of PV power through the common dc-link with the zero-sequence voltage injection technique to further enhance the system's power balancing capability. In this study, the power balancing problem in the hybrid-CHB PV inverter is formulated, and the power balancing capabilities of the proposed methods are analyzed and compared with existing techniques. The results demonstrate substantial improvements without incurring additional hardware costs. Simulation and experimental results under various power imbalance scenarios validate the effectiveness of the proposed methods.