反向恢复电荷分散性对直流换流阀的影响

直流换流阀是直流输电的核心设备，它的设计性能直接影响整个直流系统的优劣。而晶闸管的反向恢复特性是阀设计时考虑的重要因素之一。为满足耐压要求，换流阀需多只晶闸管串联，但每只晶闸管的反向恢复电荷均不同，这种电荷分散性将引起晶闸管级端电压的不同。首先分析直流换流阀关断时刻反向恢复电荷差异对晶闸管级端电压的影响。在此基础上，分别分析反向恢复电荷分散性对阀最小触发电压和最小关断角的影响，推导其理论公式，并通过仿真验证公式的准确性。最后，得出在系统条件一定的情况下，阀设计时对所选用晶闸管的反向恢复电荷分散性的一般要求。

Influence of Thyristor Reverse Recovery Charge Dispersity on HVDC Valves

Thyristor valve is a key device of HVDC transmission system, the design performance of which can directly affect that of the whole DC system whilst thyristor reverse recovery characteristic can be an important factor when designing valves. In most HVDC applications, thyristors are seriesly connected so as to establish required valve voltage withstand capabilities. However, the reverse recovery charges of the seriesly connected thyristors vary and this charge dispersity will result in different thyristor terminal voltages. In this paper, the influence of the aforementioned charge dispersity at valve turn-off on thyristor terminal voltages is illustrated. Based on the illustration, influence of the charge dispersity on valve minimum firing voltage and minimum extinction angle is then analyzed. Meanwhile formulas are formed and the accuracy of which is verified through digital simulation. Finally, general requirements on thyristor reverse recovery charge dispersity dictated by valve design at giving system conditions are proposed.