Improved Double-Loop Control Strategy for Three-Phase Inverter With Unbalanced Load

Symmetry of three-phase output voltage is one of the essential requirements for three-phase inverter. Conventional double-loop control strategy has a good control effect on the output voltage waveform during load balancing. But in case of load imbalance, the output voltage contains negative sequence component, which cannot achieve three-phase inverter output voltage balance. Therefore, this article proposes an improved double-loop control strategy that decomposes the output unbalanced voltage into positive and negative sequence component, and then controls the positive and negative sequence component separately in the dual synchronous rotating coordinate system, so that the negative sequence component tracks the zero reference voltage without static difference, effectively improving the ability of the three-phase inverter to carry unbalanced loads. The simulation and experimental results verify the correctness of the proposed control method.