Distributed Control Structure for Hybrid DC bus Cascade H-bridge Photovoltaic Grid-connected Inverters

In a three-phase Cascaded H-Bridge (CHB) photovoltaic (PV) inverter, factors such as uneven solar irradiation intensity or non-uniform ambient temperature can cause an imbalance in the output power of different PV arrays. This power imbalance among the three phases can further lead to unbalanced grid currents, resulting in severe distortion and deformation, making it difficult to meet grid compliance requirements. This power imbalance among PV modules leads to an imbalance in the three-phase power, further causing the grid currents of the three phases to become unbalanced or even severely distorted, failing to meet grid regulations. Existing solutions typically focus on improving control strategies. This paper, based on a hybrid CHB PV grid-connected inverter, proposes a novel control strategy. Unlike traditional methods, this approach applies different control methods to different inverters within the hybrid inverter system. With the proposed control strategy, the inverter can still deliver three-phase balanced currents with low harmonics to the grid, even under phase power imbalance conditions. Finally, simulation results verify the feasibility of the control strategy for the hybrid DC bus CHB PV grid-connected inverter.