Control Method for Improving the Robustness of Grid-Connected Inverter in High Voltage Power System

In high-voltage and high-power systems, LCL filter is been widely used because its small filter inductance, which can effectively reduce the system volume and loss. When the power grid frequency fluctuates, the LCL inverter with traditional repetitive control CRC has the problem of decreasing the dynamic response speed and deviating the resonant frequency from the actual frequency. Because the problem that the existing inverter control strategy can not adapt to the frequency fluctuation of power grid quickly and accurately under the digital control system must be solved, a beat free repeat control strategy based on frequency self-adaptation was proposed. At the beginning, this paper gives the electrical topology. At the same time analysis its mathematical model under high voltage system. Moreover, the weighted average current (WAC) based deadbeat (DB) control is proposed in the current inner loop to make the system easy to analysis. Furthermore, in order to effectively suppress the disturbance, the plug-in repetitive controller is added to the aforementioned controller lowers the total harmonic distortion (THD) and make sure the stability of the LCL inverter. Finally, the simulation demonstrates that the proposed control method can greatly simplify the synthesis of inverter current controller, make the resonance peak under a low level, ensure the accuracy and rapidity of the controller, and provide a good and stable current control scheme for the LCL inverter under high voltage power system.