In order to improve the low voltage ride through level of the low voltage auxiliary frequency converter in the thermal power plant and effectively solve problems like the inaccurate time of voltage drop device, which is controlled by the switching structure of the traditional multi-winding transformer, and large inrush current during the closing process, a 30 kW testing device for low voltage auxiliary frequency converter in the thermal power plant is developed and a three-phase four-wire back-to-back power electronic topology is designed, together with adaptive fuzzy PI control algorithm. They can accurately set the voltage dip amplitude and time, achieving automatic cycle test controlled by upper computer. A low voltage ride through scene experiment has been carried out on low-voltage auxiliary frequency inverter both before and after the transformation in a thermal power plant in Jiangxi Province. It proves that the dynamic response speed of power electronic voltage drop device is less than 5 ms, the inverter output voltage harmonic content is less than 0.5%. What's more, the operation is convenient and the protection strategy is complete and reliable.%为了提高火电厂低压辅机变频器低电压穿越水平,有效解决传统多绕组变压器切换结构的电压跌落装置控制跌落时间不精确、合闸过程励磁涌流大等诸多问题,研制了容量为30 kW的火电厂低压辅机变频器低穿测试装置.设计了三相四桥臂背靠背电力电子拓扑结构,采用自适应模糊PI控制算法,准确设置电压跌落幅值及时间,通过上位机控制实现自动循环周期测试.装置在江西某火电厂开展低压辅机变频器改造前后低电压穿越现场实验,证明电力电子式电压跌落装置动态响应速度小于5 ms,逆变输出电压谐波含有量小于0.5%,操作便捷、保护策略完备可靠.
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