弱电网下LCL型并网逆变器高鲁棒性并网电流反馈有源阻尼策略

High Robustness Grid Current Feedback Active Damping Strategy for LCL-type Grid-connected Inverter in Weak Grid

并网电流反馈有源阻尼(grid-current-feedback-active-damping,GCFAD)策略可以在不增加额外传感器的前提下,有效抑制LCL型并网逆变器的谐振尖峰。在电网电压畸变的工况下,GCFAD策略往往与电网电压前馈策略同时使用以改善并网电流质量。然而,通过研究发现,传统GCFAD策略等效虚拟阻抗在中低频段的正阻特性会导致并网逆变器输出阻抗在中频段产生一定的相位滞后,从而降低了系统在电网电压畸变且附加电网电压前馈策略的情况下,对电网阻抗变化的鲁棒性。为了解决这一问题,提出了一种高鲁棒性并网电流反馈有源阻尼(high robustness grid-current-feedback-active-damping,HR-GCFAD)策略,使虚拟阻抗在高频处呈现正阻特性以抑制LCL谐振尖峰,增强了系统的稳定性;在中低频段呈现负阻特性以提高系统中频段输出阻抗相位,进而提高了系统在附加电网电压前馈策略时对电网阻抗变化的鲁棒性。理论分析和实验结果充分验证了所提策略的有效性。

The grid-current-feedback-active-damping control strategy(GCFAD)has the function to effectively suppress the resonance peak of the LCL-type grid-connected inverter without requiring additional sensors.The GCFAD strategy is often used together with the grid voltage feedforward strategy to improve the quality of the grid current in a weak and disturbing grid.However,it is found that the positive resistance characteristics of the virtual impedance in the middle and low frequency bands under the traditional GCFAD strategy may cause a phase lag of the output impedance in the middle band,which reduces the robustness of the system when the grid voltage feedforward strategy is involved.In order to solve this problem,this paper proposes a high robustness grid-current-feedback-active-damping strategy(HR-GCFAD),which makes the virtual impedance exhibit positive resistance characteristics at high frequencies to suppress the LCL resonance peak and strengthen the stability of the system.It exhibits negative resistance characteristics in the middle and low frequency bands,which improves the robustness of the grid-connected inverter in a weak grid.Theoretical analysis and experimental results fully verify the effectiveness of the proposed strategy.