直驱型变速恒频风力发电系统中零序环流的研究

Zero-sequence Current in Direct Drive Variable-speed Constant-frequency Wind Energy Conversion Systems

对采用多相永磁同步发电机的大功率直驱型变速恒频风力发电系统进行研究,介绍了适合于大功率直驱型风力发电系统的结构。系统采用了多重化的AC-DC-AC变换器,以减少每只绝缘栅双极晶体管(insulated gate bipolar transistor,IGBT)上的电流和流入电网的谐波电流,但并联多重化变换器中存在的零序环流会增加功率半导体器件损耗。推导了零序环流的数学模型,分析零序环流的产生原因,提出一种基于零轴电流反馈控制的零序环流控制策略。该控制策略不需要改变电路拓扑,算法实现简单,易于模块化的设计,且适用于基于传统正弦脉宽调制的多重化变换器的控制。仿真和实验结果表明,该方法能够很好地控制零序环流,减少对系统的损害。

A high power direct-drive variable-speed constant-frequency wind energy conversion system based on multi-phase permanent magnet synchronous generator （PMSG） was researched. The configurations of wind energy conversion systems which are suitable for high power direct-drive wind energy conversion systems were introduced. In order to reduce the current of each insulated gate bipolar transistor （1GBT） and reduce the harmonic current to the grid, a multiple AC-DC-AC converter was used. But zero-sequence circulating currents in the parallel multiple conveners increase the loss of the power semiconductor. In the paper, the mathematic model of zero- sequence current was educed and the reason of zero-sequence current was analyzed. A zero-sequence current control strategy based on o-axis current feedback control was proposed. The control strategy does not change the topologies of the circuit. It is easy to implement and modular design. It is suitable for the mutiple conveners based on traditional sinusoidal pulse width modulation （SPWM）. Simulation and experimental results prove that the proposed method could control the zero-sequence circulating current to reduce the damage of the system.