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To address the instability issues of LCL-type wind power inverter's operation under weak grid conditions, stability control methods are investigated in this paper. Based on an inverter impedance model that… Click to show full abstract
To address the instability issues of LCL-type wind power inverter's operation under weak grid conditions, stability control methods are investigated in this paper. Based on an inverter impedance model that considers an inner current control loop, a precise impedance model that considers dynamic characteristics of dc bus voltage and a reactive power outer loop is created in this paper. The phasor diagram method and an analytical method are used to interpret frequency characteristics of the inverter output impedance. The impedance analysis results show that the instability of the inverter in a weak grid has a weak correlation with the LCL filter parameter and a strong correlation with the inner and outer control loops. Phase-locked loop bandwidth reduction improves inverter's operation stability to some extent. However, it also reduces the inverter's tracking and anti-interference performance. Therefore, a capacitor current-feedback-based stability control method is proposed in this paper. The feasibility of the proposed control method is proven via general Nyquist-criteria-based impedance analysis. Finally, an RT-LAB hardware loop test platform is created to verify the validity of impedance modeling proposed in this paper and the effectiveness of the stability control strategy.To address the instability issues of LCL-type wind power inverter's operation under weak grid conditions, stability control methods are investigated in this paper. Based on an inverter impedance model that considers an inner current control loop, a precise impedance model that considers dynamic characteristics of dc bus voltage and a reactive power outer loop is created in this paper. The phasor diagram method and an analytical method are used to interpret frequency characteristics of the inverter output impedance. The impedance analysis results show that the instability of the inverter in a weak grid has a weak correlation with the LCL filter parameter and a strong correlation with the inner and outer control loops. Phase-locked loop bandwidth reduction improves inverter's operation stability to some extent. However, it also reduces the inverter's tracking and anti-interference performance. Therefore, a capacitor current-feedback-based stability control method is proposed in this paper. The feasibility o...