改善双馈感应发电机无功特性的变阻值撬棒保护方案

撬棒保护的接入及其电阻值会改变低电压穿越期间双馈感应发电机(DFIG)的无功功率动态特性,由此将影响风电场周边区域电网电压稳定性。针对这一问题,详细分析不同电网电压跌落水平和低电压过渡不同时期撬棒保护接入对DFIG无功特性的影响机理及其变化规律。提出了一种改善机组无功特性的变阻值撬棒保护方案,制定了该方案的撬棒阻值整定方法及其投切控制策略,并进行仿真对比研究。仿真结果表明,相比以限流为目标的传统撬棒保护和以尽快恢复机组可控性的主动式撬棒保护,所提撬棒保护方案不仅能在故障持续期间缩短撬棒投入时间,减少撬棒投入期间DFIG吸收的无功功率,提升出口电压。同时也能最大限度降低故障切除时的DFIG无功振荡峰值,加速电网电压恢复,有助于系统区域电压稳定性的提升。

Crowbar protection scheme based on dynamic resistance for reactive power improvement of doubly fed induction generator

The activation of crowbar protection and its resistance value will alter the reactive power dynamic characteristics of Doubly Fed Induction Generator (DFIG) during the Low Voltage Ride Through (LVRT) period, which will affect the wind farm district grid voltage stability. To solve this problem, the influence mechanism of the crowbar protection on DFIG reactive characteristics and its variation law under different grid voltage sags and low voltage transition periods are analyzed in detail. Then, a novel crowbar protection scheme based on dynamic resistance for reactive power improvement of DFIG is proposed. And the corresponding crowbar resistance setting method and switching control strategy are established. Finally, the comparative studies are carried out. Simulation results show that compared with the traditional crowbar protection for current limitation and the active crowbar protection for generator controllability recovery, the proposed crowbar protection scheme can shorten the activation time of the crowbar, reduce the reactive power absorbing, and improve the terminal voltage of the DFIG during the fault. It can also minimize the oscillation peak values of the reactive power, and consequently accelerate the grid voltage recovery after clearing the fault, which is helpful for enhancement of the system district voltage stability. This work is supported by National Natural Science Foundation of China (No. 51577096 and No. 51761135015).