整流侧换流母线电压恢复导致逆变器换相失败的机理分析

交直流系统中整流侧换流母线电压恢复会引起直流电流增大,从而导致逆变器换相失败。为了解决该问题,文中首先以CIGRE HVDC标准测试系统为例,分析了电压恢复期间逆变侧控制系统的控制特性,发现由定电流控制切换为定关断角控制瞬间及之后一段时间内,直流电流较大及增速过快从而引起电流偏差控制输出较小且快速降低是诱发换相失败的重要原因。其次,提出了一种通过改进定关断角控制器以改善整流侧换流母线电压恢复导致关断角过小的控制方法。最后,在PSCAD/EMTDC电磁暂态仿真软件中利用CIGRE HVDC标准测试模型仿真验证了所提方法的有效性,由仿真结果可知该方法能有效抑制由整流侧换流母线电压恢复导致的逆变器换相失败。

Mechanism analysis of inverter commutation failure caused by voltage recovery of commutation bus at rectifier side

The voltage recovery of commutation bus on the rectifier side in AC/DC system always leads to the increases of DC current, thus resulting in the inverter commutation failure. In order to solve this problem, the CIGRE HVDC benchmark model is firstly taken as an example to analyze the control characteristics of control system on the inverter side during voltage recovery. The main reason of commutation failure is that the value of output current error control is small and rapidly reduces due to the large and fast increase of DC current after the control mode is switched from constant current control to constant extinction angle control. The extinction angle is small and always affected by the voltage recovery of commutation bus on the rectifier side, so that a control method is proposed to increase the extinction angle by improving the current error controller. Finally, the CIGRE HVDC benchmark model is used in PSCAD/EMTDC electromagnetic transient simulation software to verify the effectiveness of the proposed method. The simulation results show that the proposed method effectively suppresses the commutation failure caused by the voltage recovery of commutation bus on the rectifier side.