一种抑制连续换相失败的定关断角加速控制方法

针对逆变侧交流故障引发高压直流输电系统连续换相失败问题，通过分析首次换相失败恢复过程中的电气量和控制量变化规律，明确了恢复过程中定电流、定关断角、电流偏差控制器之间配合不当是引发连续换相失败的重要原因。同时，在不对称故障后，由交流负序电流引起的直流2次谐波电流会导致控制切换点滞后，增加连续换相失败的风险。基于此，提出了一种能增强控制器配合效果的定关断角加速控制方法。该方法能根据换相恢复过程自适应投切，利用关断角偏差动态调整关断角控制指令值，提前实现控制切换，降低切换后不当控制影响。同时，通过陷波器降低谐波电流从而减弱触发角波动对控制器切换的不利影响。该方法能提升控制器间配合效果，提升直流系统抵御连续换相失败能力。在CIGRE标准测试模型中，验证了理论分析的正确性和优化方法的有效性。

A constant extinction angle acceleration control method for suppressing continuous commutation failure

There is a problem of continuous commutation failure (CCF) of an LCC-HVDC transmission system caused by an AC fault on the inverter side. Thus this paper first analyzes the variation of electrical quantity and control quantity in the recovery process of the first commutation failure (FCF), and clarifies that improper cooperation between constant current (CC), constant extinction angle (CEA) and current error control (CEC) in the recovery process is an important cause of CCF. After the asymmetrical fault, the DC second harmonic current caused by the AC negative-sequence current will lead to the delay of the control switching point and increase the risk of CCF. Based on this, a constant extinction angle acceleration (CEAA) control method is proposed, one which can enhance the coordination effect of controllers. This method can adaptively switch according to the commutation recovery process. It uses the extinction angle deviation to dynamically adjust the CEA command, realizes the control switching in advance, and reduces the influence of improper control after switching. At the same time, the method reduces the harmonic current by the notch filter. This can reduce the adverse effect of controller switching by reducing the firing angle wave. This method can improve the coordination effect between controllers, thus improving the ability of a DC system to resist CCF. The correctness of the theoretical analysis and the effectiveness of the optimization method are verified in the CIGRE model.