中文摘要：

电力电子变压器（PET）的并联运行对提高电力系统供电的可靠性和稳定性具有重要的意义。为了解决并联系统的环流和负荷均分的问题,将下垂控制理论引入电力电子变压器并联的控制策略中,传统的下垂控制无法适用于线路阻感比较大的低压电网。提出通过控制参数的设计使系统等效输出阻抗呈感性,可以改善系统的阻感比,从而满足下垂控制的需要,同时提高系统运行稳定性。在Matlab/Simulink中建立了两台PET的并联系统并进行仿真研究,结果表明,该控制策略可以在保持输出电压幅值和频率稳定的前提下很好地抑制并联环流,并实现负荷的合理分配,且具有良好的动态性能。

英文摘要：

The parallel operation of power electronic transformer （PET） is of great significance to improve the reliability and stability of power supply system. In order to solve the problems of circulation and load sharing in parallel system, the droop control theory is introduced into the control strategy of power electronic transformer in parallel, but the traditional droop control can not be applied to the low voltage power grid with large resist- ance. It is suggested that the equivalent output impedance of the system can be improved through the design of control parameters, which would meet the needs of droop control and improve the stability of the system. A par- allel system with two PET is built in Matlab/Simulink and the simulation is carried out. Results show that the control strategy can restrain the parallel circulation and realize the reasonable distribution of load in the condi- tion of keeping output voltage amplitude and frequency stability, and has good dynamic performance.