多端柔直换流站高频谐振及传播机理分析与抑制OACSTPCD

To address the issue of high-frequency resonance in multiterminal flexible direct current(DC)transmission systems caused by unloaded line input,a simplified impedance model is established for MMC in the high-frequency range.Based on the impedance analysis,the electrical mechanism of high-frequency resonance in a single MMC caused by an unloaded line input was analyzed.The analysis shows that owing to the unloaded line input,the MMC AC-side equivalent impedance exhibits negative damping in the high-frequency range,leading to high-frequency resonance.Joint modeling was then conducted for the receiving converter stations under different control methods.By analyzing the propagation path of high-frequency resonance energy between stations and its impact on the operation of receiving MMCs,research has shown that high-frequency resonance on the AC side of MMC can affect other MMCs through DC lines.The degree of the impact is related to the external control method.To solve the problem of high-frequency resonance,a suppression method involving the addition of a bandstop filter to the voltage feedforward was adopted to eliminate the negative damping of the MMC at the high-frequency resonance point,complete the impedance reshaping of the oscillating MMC,effectively suppress the high-frequency resonance of the MMC,and reduce the negative impact of high-frequency resonance energy propagation on other MMCs.Finally,the accuracy of the MMC high-frequency resonance analysis and the effectiveness of the corresponding suppression method were verified using the RT-LAB5600 real-time online simulation platform.