基于定子电流正弦化的双馈风电系统低电压穿越强励控制

基于Crowbar电路的低电压穿越实现了双馈风电机组的系统保护和不脱网运行。Crowbar电路的应用使得网压跌落时转子变流器闭锁,转子电流处于暂态过程。针对采用Crowbar电路实现低电压穿越过程中,双馈风电机组系统对电网产生暂态电流冲击而存在的不足,文中提出一种基于转子电流源控制的低电压穿越强励控制策略,通过强励实现低电压穿越过程定子暂态直流磁链分量的补偿,以实现低电压穿越过程中定子电流的正弦化。由于在静止坐标系中引入直流磁链补偿,在转子dq旋转坐标系控制方程中引入了工频交流分量,因此文中提出了一种基于多分量增益的比例谐振(PR)并联调节器,并通过该并联调节器的闭环传递函数分析对调节器参数进行整定,实现了控制带宽范围内直流电流分量与工频交流电流分量的无静差控制。仿真及实验结果验证了理论分析的正确性,为双馈风电系统的低电压穿越控制提供了一种高性能的控制策略。

Forced Excitation Control of Doubly-fed Wind Power Systems During Low Voltage Ride-through Based on Sine Wave Shaped Stator Current

The system protection and continuous operation of grid connected doubly-fed induction generators (DFIGs) are realized by the low voltage ride-through (LVRT) based on crowbar circuit. The semiconductors of rotor side converter should be switched off during LVRT when the crowbar is fired, while the rotor current is in transient. In view of the inrush current caused by the traditional LVRT strategy applying crowbar, the control method for transient rotor current is analyzed. Based on the forced excitation strategy, the transient stator direct current (DC) flux linkage is compensated and the sine wave of the stator current during LVRT is effectively achieved. Due to the DC flux linkage compensation, the current of power frequency component is produced in the dq rotating coordinate system. The gain control of multi-components using parallel proportional resonant controller is proposed. Through the analysis of the closed loop transfer function of the proposed controller and the parameter tuning, the zero steady-state error control of the mixed DC and power frequency current is achieved. Simulation and experimental results validate the theoretical analysis, which provides a high performance control strategy for controlling LVRT of the doubly-fed wind power system.