送端换流母线电压上升影响受端换相的机理及抑制措施

Mechanism and Suppression Measures for Receivingend Commutation Affected by Voltage Rise of Sendingend Converter Bus

摘要:

为避免由送端换流母线电压上升引起逆变器关断角减小导致换相失败，分别从电气量变化特性和无功交换特性研究了其发生机理。基于推导建立的关断角表达式，分析发现送端换流母线电压上升会引起直流电流增大从而导致关断角减小；同时直流电流的增大会引起逆变器无功消耗增加，导致受端换流母线电压跌落，进一步导致关断角减小，诱发换相失败。因此，提出了一种通过改进送端控制器以抑制换相失败的措施。该措施在送端换流母线电压上升时增大整流器触发角以抑制直流电流的上升，同时增大整流器无功消耗从而减缓送端换流母线电压的上升。基于PSCAD/EMTDC电磁暂态仿真平台，利用CIGRE HVDC标准测试模型仿真验证了理论分析的正确性和抑制措施的有效性。

Abstract:

In order to avoid the commutation failure due to the decrease of extinction angle of inverter caused by voltage rise of converter bus at sending end, the occurrence mechanism is studied from the variation characteristics of electrical quantity and the exchange characteristics of reactive power respectively. Based on the derived expression of extinction angle, it is found that the voltage rise of converter bus at sending end will increase DC current, which will lead to the decrease of extinction angle. At the same time, the increase of DC current will lead to the increase of reactive power consumption of inverter, resulting in voltage drop of converter bus at receiving end, further leading to the decrease of extinction angle and inducing commutation failure. Therefore, a measure to suppress commutation failure by improving controller at sending end is proposed. This measure increases the trigger angle of rectifier when the voltage of converter bus rises at sending end to suppress the rise of DC current and increases the reactive power consumption of rectifier, so as to slow down the voltage rise of converter bus at sending end. Based on PSCAD/EMTDC electromagnetic transient simulation platform, CIGRE HVDC benchmark model is used to verify the correctness of theoretical analysis and the effectiveness of suppression measures.