永磁直驱变速风电系统的控制及稳定性分析

Control and Stability Analysis for the Permanent Magnetic Synchronous Generator Based Direct Driven Variable Speed Wind Energy Conversion System

分析了传统功率控制方法下永磁直驱变速风电系统的稳定性,提出一种改进型功率控制方法,以抑制系统低频振荡并提高系统稳定性。分析表明,在功率控制模式下,传动系统的动态会引起发电机转速的低频谐振,导致系统输出功率低频振荡,影响风电系统和电力系统的稳定运行;降低发电机转矩环带宽可以提高系统的稳定裕度,却会降低系统的响应速度。所提出的改进型功率控制方法通过变流器开关模型重构直流母线电流,并基于该观测值构成发电机转矩控制环的前馈补偿项。该方法可有效降低系统的低频振荡,提高系统稳定性。仿真实验验证了理论分析和改进型功率控制方法的有效性。

The stability issues of the permanent magnetic synchronous generator （PMSG） based wind energy conversion system （WECS） was discussed. And a novel power control strategy was proposed for the vibration depression and stability improvement. Due to the drive train dynamics, the generator speed is usually prone to a low-frequency vibration during dynamic state in the power control mode. The vibration can result in an oscillation of the output power which is fatal to the stability of WECS and power systems. Reducing the control band width for generator torque loop can help to improve the system stability but the power response is therefore deteriorated Based on the DC link current restored with the switch model of the back-to-back converter, additional feed forward compensator was included in the torque loop to formulate a novel power control strategy. The proposed strategy could effectively damp the speed and power vibration thus improving the system stability. The simulation results verify that the stability analysis and the compensation strategy are valid for the PMSG based WECS.