并联逆变器的短路保护策略

常用的短路保护方案是正常下的恒压模式和异常下的恒流模式相结合的方案。因并联逆变器各模块参数的差异性,短路消除后退出恒流模式的时间不一致产生较大的环流,尤其在轻载情况下易引起功率倒灌,严重时导致直流电压过电压保护停机。针对该问题,提出利用均值电压和瞬时电流值相结合改进策略,且多台并联逆变器同时在同步信号的上升沿(或下降沿)退出恒流模式进入恒压模式,并抬高起始电压得到快速恢复额定电压。两台400kVA/50Hz的逆变器对比实验结果证明了改进策略的有效性。

Short-Circuit Protection Strategy for the Parallel Inverters

The commonly used short circuit protection strategy is to combine the constant voltage mode(CVM) in normal situation and the constant current control mode(CCM) in abnormal situation.However,the output characteristics discrepancy and different control parameters cause the time variance retreating from CCM to CVM for the parallel inverters,which results in differences in voltage and large circulating currents.It easily causes power flooding inversely,pumping of DC voltage,and over-voltage protection in light load,which can not satisfy the non-stop requirements during short circuit.The proposed strategy of retreating from CCM in terms of the average voltage and instantaneous current is introduced in this paper.It states that several parallel inverters retreat simultaneously from CCM and enter CVM at the rising edge(or failing edge) of synchronous signal.The initial voltage is increased to reduce the recovery time from CCM,when the short circuit is disappeared.The compensation of the experimental results on two 400kVA/50HZ inverters verifies the effectiveness of the proposed strategy.