多维因素综合作用下换流阀晶闸管载流子迁移恢复特性解析及关断机理研究

Carrier Migration and Recovery Characteristics Calculation of Converter Valve Thyristor and Its Turn-off Mechanism Considering Multi-dimensional Factors

明确换流阀晶闸管在逆变侧交流故障期间的关断特性及关断机理对抑制换相失败十分必要。影响晶闸管关断的主要因素有正向电流、电流过零点下降率和结温等,为明确上述因素综合作用对晶闸管关断特性的影响机理,该文首先基于考虑器件物理特性的晶闸管详细关断模型研究其换相关断过程,搭建晶闸管换相关断等效电路;研究上述因素间的作用关系及综合作用下的晶闸管关断特性,并通过对载流子迁移恢复特性的解析,获得晶闸管换相关断过程中的恢复电荷迁移特征。最后,得到使晶闸管可靠关断的阻断能力恢复时间及换相结束时剩余电荷值,以阻断能力恢复时间、临界关断角等指标定量评价各因素综合作用对晶闸管关断特性的影响程度。结果表明,在相同的换相起始条件下,当故障导致正向电流增大时,不考虑多因素综合作用的晶闸管阻断能力恢复时间偏长,会对系统提出更高的关断要求;仅考虑正向电流和电流过零点下降率二者综合作用时阻断能力恢复时间偏短,会增加换相失败误判风险;考虑三种因素综合作用后所得到的晶闸管阻断能力恢复时间更加准确。

It is necessary to clarify the turn-off characteristics of thyristor in valve during AC fault at the inverter side to restrain commutation failure.The main factors affecting the turn-off process of thyristor are forward current,zero-crossing decline rate and junction temperature,etc.In order to clarify how the factors above comprehensively influence on turn-off characteristics,this paper firstly studies the turn-off process based on the turn-off model considering the physical characteristics of the device,and the equivalent circuit of turn-off process is then developed.And the relationship between various factors and the turn-off characteristics are researched.By calculating the carrier,the charge during the turn-off process is obtained.Finally,the blocking capacity recovery time for reliable turn-off and the residual charge at the end of commutation is given.The comprehensive effect of the factors on the turn-off process is quantitatively evaluated taking the blocking ability recovery time,critical margin angle,and etc.,as indexes.The results indicate that,under the same commutation condition,when the fault leads to the increase of forward current,the blocking ability recovery time gets longer assuming that the effect of multi-dimensional factors is not considered,which will lead to higher turn-off requirements for the system.The blocking ability recovery time gets shorter if the effect of forward current and zero-crossing decline rate is the only factor considered,which may result in the misjudge of the commutation failure.Considering the comprehensive effect of above factors,the blocking ability recovery time is more accurate.