Parameters Design and Optimization for LC-Type Off-Grid Inverters With Inductor-Current Feedback Active Damping

In this paper, the stability of LC-type voltage source inverter is investigated, with the emphasis focused on the LC resonance. It has been found that the traditional capacitor-voltage inductor-current dual-loop control is unstable when the resonance frequency is higher than one-sixth of the sampling frequency. In addition, due to the coupling between current inner loop and voltage outer loop, it is difficult to design control parameters to ensure the system stability in traditional dual-loop control. In order to develop a systemic design principle, the capacitor-voltage control with inductor-current feedback active damping evolved from traditional dual-loop control is analyzed in detail. The mathematic model is established to reveal the reason of instability, and the stable regions are identified. Moreover, the optimal damping coefficient is also derived to enhance the system damping performance. Finally, the experimental results are provided to verify the effectiveness of the proposed method.