基于关断时间的静止变频器换相失败抑制技术

Research on Static Frequency Converter Commutation Failure Suppression Technology Based on Turn-off Time

静止变频器广泛应用于抽水蓄能电站、燃气轮机、泵站等电动机启动。实际运行中常因晶闸管性能下降引起关断角的余量不足,继而发生换相失败。为抑制换相失败,提出一种基于晶闸管换相关断时间偏差量的控制策略;并设计了控制决策函数,依据晶闸管换相关断时间的偏差量情况,选择无输出、补偿增大关断角、降低直流电流3种形式,抑制晶闸管换相失败。当偏差量小于死区值时,无输出;当偏差量超过死区值时,增大关断角;当关断角接近功率因数极限值时,降低直流电流。工程现场验证表明,该策略在静止变频器最小拖动电流允许的晶闸管换相的余量角范围内,可避免因晶闸管性能下降导致的换相失败。

Static frequency converter is widely used in pumped storage power station,gas turbine,pump station and other motor starting.In practice,due to the decrease of thyristor performance,insufficient switching angle margin results in failure of commutation.In order to suppress commutation failure,a control strategy based on the time deviation of thyristor commutation is proposed.The control decision function is designed.According to the deviation of the thyristor’s change-related break time,three kind of schemes were chosen:no output,compensation to increase of turn-off angle,and decrease of DC current.When the deviation exceeds the value of the dead zone,the turn-off angle is increased.The DC current is reduced when the turn-off angle approaches the power factor limit.The project site verifies that this strategy can avoid commutation failure caused by the degradation of thyristor performance within the thyristor commutation margin angle allowed by the minimum drag current of the static inverter.