An Active High Frequency Damping Scheme for the Current Control of L Filter-Based Grid-Connected Inverter

A virtual high frequency damping (VHD) method is proposed in this paper for the improving of L filter-based grid-connected inverter’s stable margin as well as its output current waveform performance. The precise frequency domain model of system, which involves pulse width modulation (PWM) and digital control delay, is sophisticated studied. Based on which, the quantitative relationship between the proportional (P) control gain and the inductance value as well as the digital control delay is revealed, and the system global control gain margin is obtained. Furthermore, the stability problems caused by the larger value of control gain under the traditional control method and a current sampling prediction (CP) method are studied, respectively. Therefore, the guidelines for the designing of system’s virtual damping is provided, and VHD method as well as its phase compensation approach are thereby proposed to attenuate the oscillation of system output current, in particular of the high frequency oscillation, and to improve system performance in terms of expanding the current loop operating bandwidth and increasing the system stable margin. The simulation and experimental results both clearly validate the correctness and feasibility of the proposed VHD method.