基于双馈风力发电机组轴电流抑制与释放的研究

Research on Suppression and Release of Shaft Current Based on Doubly Fed Wind Turbine

双馈型风力发电机组PWM变频调制过程中产生的共模电压与发电机内部杂散电容耦合形成的轴电流,如果不能有效抑制和释放,将会严重威胁机组的安全稳定运行。针对这一技术难题,研究分析了双馈机组轴电流的成因及产生的危害,提出了采用共模扼流圈和多点接地的方案抑制并释放轴电流,并利用案例进行了实施效果验证。研究得出,共模扼流圈和多点接地的方案可有效保护发电机轴承免受损坏。在变频器与发电机之间传输电缆安装共模扼流圈,可有效降低IGBT开关过程中产生的du/dt高频EMI,衰减并抑制共模电流。同时,利用发电机驱动端安装多点接地碳刷,以串联的方式接入到接地回路,对降低轴电压具有显著效果。

If the common mode voltage generated in the PWM frequency conversion modulation process of doubly fed wind turbine and the shaft current formed by the coupling of the stray capacitance inside the generator cannot be effectively suppressed and released,it will seriously threaten the safe and stable operation of the unit.Aiming at this technical problem,this paper studies and analyzes the cause of the shaft current of the doubly fed unit and its harm.It puts forward the scheme of using common mode choke and multi-point grounding to restrain and release the shaft current.It also verifies the implementation effect with a case.It is concluded that the scheme of common mode choke and multi-point grounding can effectively protect the bearing of generator from damage.The common mode choke is installed in the transmission cable between the frequency converter and the generator,which can effectively reduce the du/dt high-frequency EMI produced in the process of IGBT switching,attenuate and can suppress the common mode current.At the same time,the multi-point grounding carbon brush is installed at the driving end of the generator,and connected to the grounding circuit in series,which has a significant effect on reducing the shaft voltage.