A Robust Stability Approach for Current-Controlled Grid-Connected Inverters Using PCC Voltage Feedforward Method

Stability of LCL-filtered grid-connected inverters could be threatened by the resonance of the LCL filter. The situation may even become worse under weak grid scenarios, where the grid impedance variations may locate the resonance frequency in the unstable region. Therefore, the control system should be designed to cope with these problems. In this paper, a simple and robust method based on feedforwarding the point of common coupling (PCC) voltage is proposed, which guarantees the stability of the system regardless of the grid impedance variation. The proposed method is based on the passivity of inverter output admittance, which could eliminate the non-passive region below the Nyquist frequency. Also, it does not need any passive or active damping methods, which in turn, reduces the cost and enhances efficiency. Experimental results on a laboratory prototype are provided to show the accuracy of the analysis and verify the proposed method.