The Research on Control Strategy of Islanded Inverter Based on Output Impedance Optimization

With the widespread adoption of renewable energy, the single-phase islanded inverter, as a core device for power conversion, plays a crucial role in determining the quality of output power and overall system stability. To address the resonance issues caused by the LC output filter and the AC-side instability resulting from DC-side voltage fluctuations, this paper proposes a triple-loop composite control strategy based on DC voltage feedforward. The strategy employs dual quasi-PR controllers for voltage and current to achieve zero steady-state error tracking of the fundamental component, and introduces an active damping loop based on capacitor current to suppress high-frequency resonance. Using frequency-domain impedance analysis, an output impedance model is established to reveal the influence of control parameters on system stability. Simulation results show that under a 1 kΩ load, the output voltage THD can be maintained below 0.9%, and under nonlinear load conditions, the THD is as low as 0.73%, significantly outperforming conventional control schemes.