A Multi-Loop Control Strategy for a Single-Phase In-Verter Supplying Nonlinear Loads

A multi-loop control strategy for a single-phase in-verter used with nonlinear loads is proposed. In this control strategy, the outer loop constructs a virtual voltage component that leads the reference voltage by 90° to form a d-q coordinate system. The steady-state DC components of the fundamental out-put voltage in the d-axis and q-axis are obtained through orthog-onal projection. Two PI controllers are employed to control the DC components of the d-axis and q-axis separately. The inner loop quickly adjusts the modulation signals of the inverter bridge by detecting the deviation of the output voltage, significantly re-ducing harmonic distortion. Simulation results demonstrate the effectiveness of the proposed control strategy.