An enhanced model predictive control method for single-stage three-phase transformerless grid-connected photovoltaic inverter

The single-stage transformerless photovoltaic (PV) topology is an attractive configuration as it offers high efficiency, low installation cost and smaller size. For such a configuration, the control algorithm should be designed to track the maximum power point, transform power from PV to grid, and reduce the common-mode voltage (CMV) simultaneously. However, the multi-objective handling problem will lead to degraded performance and slow response speed. In this paper, a model predictive control method with a revised switching states selection algorithm has been developed. The performance of the overall system can be enhanced under various conditions with improved efficiency. Furthermore, the CMV is greatly reduced and constrained to one sixth of the DC-link voltage. In addition, appropriate candidate region selection and pruning mechanism are employed to reduce the calculation burden of MPC. Finally, the performance of the proposed MPC method is verified by the control hardware-in-the-loop approach through OPAL real-time platform under various conditions.