直驱型风力发电变流器低压穿越控制策略研究

研究了直驱型风力发电变流器系统低压穿越控制策略。首先提出了一种对三相电量进行快速准确的正负序分离软件锁相环。在此基础上，为消除直流电压的二次谐波，采用正、负序双电流内环控制不对称运行控制策略。正负序分离软件锁相环采用了正负序级联延时信号消除法，能够实现对三相电压电流基波正负序分量在同步旋转坐标下的快速提取，并且通过选择不同的参数，可以滤除任何次数谐波的干扰。该方法无需采用滤波器，从而同时具备了稳态精确性和动态快速性。现场实验结果表明，该软件锁相环为三相并网型风力发电变流器在电网发生跌落及谐波畸变时提供了良好运行控制提供保障，正负序双电流内环不对称运行的控制策略保证了在电网电压不对称跌落时的正负序分离控制，消除了直流电压的二次谐波。

Low Voltage Ride through Control Strategy of Direct Drive Wind Power Converter

In this paper the low voltage ride through control strategy of direct drive wind power converter is studied. Firstly a novel PLL scheme with fast dynamic response and high precision is proposed, and then, the dul-current loop control strategy was adopted to eliminate the DC voltage harmonics. The PLL scheme is based on positive-and negative-sequence cascaded delayed signal cancellation method, and the positive and negative sequence components of the fundamental voltage or current in the 3-phase system can he calculated with fast transient response, and any specified harmonic can be eliminated by choosing appropriate parameters. Perfect dynamical performance earl be achieved with no low-pass filters needed. The field experiment showed that the PLL can provide a reliable basis for the control of the grid connected PWM converters under grid voltage dip and distorted grid voltages in wind power systems and can be used in low voltage ride through control in the grid-connected wind power system. Meanwile, positive-and negative-sequence currents can be controlled respectively and DC voltage harmonics be eliminated with the use of dul-current loop control strategy.