Notch Filter-Based Active Damping Design Method of Three-phase Grid-Tied Voltage Source Inverter with Asymmetric-LCL Filter

A high-order power filter is always used to filter out harmonics in grid-injected current. Compared with other power filters, the Asymmetric-LCL(A-LCL) filter has the advantages of having a small total inductance and strong robustness. However, the resonance problem of higher-order filters may lead to instability of the system, especially in a weak power grid. Active damping strategy has the benefits of high efficiency and flexibility. Plugging in a notch filter is an effective and simple active damping method and there are no sensors. This paper introduces a notch filter-based active damping design scheme for A-LCL filter. A simulation on a 220V/6kW grid-tied inverter (GTI) system with A-LCL filter in a weak grid verifies the feasibility of the proposed scheme.