Investigation into the control methodology for three-phase LCL grid-tied inverters under conditions of asymmetric voltage

The three-phase LCL grid-connected inverter has three-phase grid-connected current asymmetry due to grid voltage asymmetry, active reactive power double fluctuation phenomenon and LCL inherent resonance spike phenomenon. Aiming at the problems of complex control structure and poor dynamic performance of double dq-axis and passive damping-based PI control strategies, this paper adopts a double dq-axis and first-order linear self-resistant control (LADRC) current loop control strategy based on inverter-side current feedback, which simplifies the complexity of the control system, and at the same time realizes the effective suppression of the maintenance of the balance of the grid current and the double fluctuations of the active/reactive power, and effectively suppresses the LCL resonance spikes. The LCL resonance phenomenon is also effectively suppressed. Comparative simulation analysis shows that this current loop control strategy has superior robustness.