Abstract:

Active damper device can effectively enhance the resonance stability of grid-connected inverters at the point of common coupling by emulating resistive characteristic.However,under weak grid conditions,the phase-locked loop of the active damper can adversely affect its emulated resistive behavior,significantly reducing its resonance stability enhancement capability and potentially introducing new resonance issues.To address these challenges,an output impedance model of the active damper considering the influence of the phase-locked loop is established.Based on this model,the impedance phase shift caused by the phase-locked loop is analyzed,and a resistive characteristic optimization strategy for the active damper is proposed to ensure that it maintains excellent resistive characteristic even under the influence of the phase-locked loop.Experimental results demonstrate that the adverse effects introduced by the phase-locked loop are effectively compensated by the proposed resistive characteristic optimization strategy.The resonance suppression capability of the active damper is significantly enhanced.The correctness of the theoretical analysis and the effectiveness of the proposed strategy are validated.

Key words: active damper, phase-locked loop, grid-connected inverter, weak grid, resonance suppression