恒速异步发电机型风电场低电压穿越能力仿真研究

Simulation Study on LVRT Ability of Constant-speed Asynchronous Generator-based Wind Farm

本文以一个机端母线设置为PQ节点的恒速异步发电机型风电场接入无穷大系统为例,对风电场接入系统线路发生三相接地短路故障时的风电场低电压穿越(LVRT)能力进行了仿真分析,研究结果显示风电场的LVRT能力主要取决于故障发生后系统维持暂态电压稳定的能力,即取决于故障切除时间ts的大小。当ts小于或等于故障极限切除时间tvc时,风电场则具备一定的LVRT能力;当系统具有较大的tvc值时,可有效提高风电场低电压穿越的持续时间;在ts≤tvc的前提下,故障切除时间越短,风电场并网点电压恢复正常水平的速度越快。当风电机组机端并联电容器组、SVC、STATCOM等无功补偿设备时,均可有效增大系统的tvc值,从而显著提高风电场的LVRT能力;其中STATCOM对风电场LVRT能力的补偿效果最好。

A simulation model is established that a constant-speed asynchronous generator-based wind farm is accessed in the infinite system and the terminal bus of asynchronous generator is set in PQ node. Base on the model we make some simulation analyses about LVRT ability of the wind farm when the 3-phase grounding short circuit fault happens in the grid connected line. The research results show that wind farm＇s LVRT ability mostly depends on the ability of maintaining transient voltage stability after the fault happened, namely depends on the fault cleating time ts. When ts is shorter than or equal to the fault critical clearing time tvc, the wind farm can have a certain LVRT ability and the greater tvc can improve the duration time of LVRT. When ts≤tvc, the shorter the fault clearing time t, is, the faster the voltage of grid connected bus recovers. When the terminal bus of the asynchronous generator parallels capacitor bank, SVC or STATCOM, the tvc can be increased effectively and the ability of LVRT can be improved obviously, and the STATCOM can obtain the best compensation effect on LVRT ability.