中文摘要：

分析了在线式不间断电源在重载切换模式下导致逆变模块故障的原因。为了抑制重载旁路切换到逆变瞬间所产生的环流,提出了一种改进的抑制环流的方法。在20 k VA三相不间断电源样机上的实验结果表明所提出的控制策略能可靠、有效地抑制不间断电源重载下模式切换产生的环流,确保逆变模块正常工作。

英文摘要：

Analyzes the reason which causes inverter fault under overload switching mode for on-line UPS. In order to restrain the circulation current caused by switching from bypass to inverter, an improved control strategy to restrict loop current is proposed. The experiment results prove feasibility and reliability of the control strategy on the prototype of three-phase 20 k VA UPS.