Digital control of a three-phase four-leg inverter under unbalanced voltage conditions

In this paper, the implementation of an innovative inverter control strategy based on the symmetrical components is presented. Symmetrical components of the inverter output voltage and current are decomposed into dq DC quantities to control a three-phase four-leg inverter. This kind of inverter can be a good choice for the applications with hybrid power system based on renewable energy used to supply unbalanced loads. The addition of a fourth leg provides an extra degree of freedom, making possible to handle the neutral current caused by the unbalanced load. Simulation results are compared with experimental results for a prototype inverter to verify the validity of the proposed control strategy.