Power Control of a Three-phase Grid-connected Inverter using a Proportional-Resonant Control Method under Unbalanced Conditions

The three-phase grid system can become unbalanced for reasons such as single-phase loads and single-phase renewable energy sources connected to the grid. This unbalance not only affects inverter operation, but also impacts other loads connected to the grid. The traditional control methods for three-phase grid-connected inverter operation such as the proportional-integral (PI) control and proportional-resonant (PR) control have been used for balanced system conditions. The technique proposed here utilizes a PR controller to balance the grid currents while simultaneously injecting a commanded power into the grid. Simulation and experimental results confirm the effectiveness of this control method.