基于波形相似度检测的换相失败预测控制改进方法

Improved Prediction Control Method for Commutation Failure Based on Waveform Similarity Detection

换相失败是高压直流输电系统常见故障之一。为抑制直流输电系统逆变器换相失败的发生,目前实际工程普遍采用换相失败预测控制(CFPREV)环节。但该环节易受故障合闸角的影响,在某些故障合闸角下,零序电压指标的变化趋势与故障严重程度变化趋势相悖,这将严重制约其启动速度,不利于换相失败抑制。文中在CFPREV基础上,提出一种基于波形相似度检测的CFPREV改进方法,利用Pearson相关系数实时表征零序电压波形变化,快速检测故障,规避了原CFPREV在某些故障合闸角下启动慢的不足。基于CIGRE标准测试模型的仿真结果表明,所提出的控制策略可以消除故障合闸角对原CFPREV的影响,提高CFPREV环节动作灵敏性,在一定程度上抑制直流输电系统首次换相失败。

Commutation failure is one of the most common faults in high voltage direct current(HVDC) transmission systems. In order to mitigate the inverter commutation failure in DC transmission systems, the link of commutation failure prediction control(CFPREV) is widely used in practical projects at present. However, this link is susceptible to the influence of the initial fault angle.At some initial fault angles, the variation trend of zero-sequence voltage index is contrary to the variation trend of fault severity,which will seriously restrict the starting speed of CFPREV and hinder the suppression of commutation failure. Based on CFPREV,an improved CFPREV method based on waveform similarity detection is proposed in this paper. Pearson correlation coefficient is used to represent the changes of zero-sequence voltage waveform in real time, so as to quickly detect faults and avoid the shortcomings of the original CFPREV which starts slowly at some initial fault angles. The simulation results based on the CIGRE standard test model show that the proposed control strategy can eliminate the influence of the initial fault angle on the original CFPREV, improve the operation sensitivity of CFPREV link, and inhibit the initial commutation failure of HVDC transmission system to a certain extent.