A Seamless Control Strategy of a Distributed Generation Inverter for the Critical Load Safety Under Strict Grid Disturbances

This paper introduces a seamless grid interconnection control strategy for distributed generations (DG) with renewable energy. Based on the performance analysis of conventional voltage and current control loops, sophisticated control strategies, which can overcome the limited capability of the DG inverter control under mode transition conditions for unknown power plants, are needed in order to protect critical loads and operate the DG inverter without grid fault trip. The proposed control strategy consists of a current controller and a feedforward voltage controller to minimize the grid overvoltage. The feedforward voltage control loop is added to the d-q axis current control loop. The proposed control strategy reduces the overvoltage stress of the renewable energy and the critical load under the grid fault. In addition, the seamless operation of the DG inverter will also enhance the stability and reliability of the grid. Real-time digital simulator-based hardware-in-the-loop experimental results and simulation results show that the DG inverter achieves the seamless mode transition under grid overvoltage conditions.