基于改进风力发电机组下的低电压穿越控制策略研究

摘要

随着风电场低电压穿越（low voltage ride though, LVRT）要求的提出，传统Crowbar技术的弊端显现出来，故障时转子侧变流器被短接，发电机定子侧失去为电网提供无功的能力。提出一种改进的双馈风力发电机组（ doubly-fed induction generator, DFIG）模型，使用 DC-Chopper，串联动态制动电阻（series dynamic braking resistor, SDBR）代替Crowbar，在故障时能够控制直流母线电压，抑制转子侧过电流，起到保护直流侧电容和转子侧变流器的作用。由于转子侧变流器不退出运行，所以在控制策略上提出了通过控制转子侧变流器来实现发电机定子侧在故障期间向电网提供部分无功支持，同时网侧变流器采用变功率因数控制，在故障情况下给电网提供主要的无功支持，实现低电压穿越。%Facing the requirements of low voltage ride through (LVRT), the disadvantages of traditional Crowbar technology appeared. In a failure, the rotor side converter (RSC) is short circuited, and the stator side of wide turbine loses its ability of providing reactive power for grid. This paper presents a new improved model of doubly-fed induction generator (DFIG) using DC-Chopper and series dynamic braking resistor (SDBR) instead of Crowbar. It can limit DC voltage and reduce the over-current of RSC, so it can protect DC capacitor and RSC. Because RSC is not out of service, in the control strategy, the RSC is controlled to make the stator side of wide turbine provide part of reactive power in a failure. At the same time the grid-side converter (GSC) operates in a state of variable power factor control. It can provide the most of reactive power to realize the LVRT.