基于二阶滑模控制的双馈风机低电压穿越研究

Second-Order Sliding Mode Control for the Low Voltage Ride-Through of DFIG-Based Wind Turbines

二阶滑模控制方法最主要的特点是其对外部干扰,尤其是电网故障和无抖振行为(不给风机传动链施加额外的机械外力),具有很强的鲁棒性,因此当风速低于额定风速时,采用二阶滑模控制对双馈风力发电机的低电压穿越(low voltage ride-through,LVRT)问题进行了研究,改进了传统滑模控制的抖振问题。首先,根据双馈电机模型和转子电压/电流的控制目标,利用super-twisting算法设计双馈电机的二阶滑模控制器。然后,根据Super-twisting算法的收敛条件给出保证该控制器收敛的增益范围。最后,通过MATLAB/Simulink仿真和对比验证1.5 MW风机在所设计的二阶滑模控制器作用下的低电压穿越性能。

The main and attractive feature of second-order sliding modes are robustness against external disturbances, the grids faults and chattering-free behavior（no extra mechanical stress on the wind turbine drive train）in particular. This paper deals with the low voltage ride through capability assessment of a doubly fed induction generator-based wind turbine using a second-order sliding mode control. In this context, this paper proposes a second-order sliding mode as an improved solution which handles the classical sliding mode chattering problem when wind speed is lower than the rated wind speed. Firstly,according to the DFIG model and the control aim of the rotor voltage/current,a second sliding mode controller is designed based on the Super-twisting algorithm. Secondly,to ensure the sliding mainfolds convergence to zero in finite times,the variation ranges of the gains are given. Finally, simulations on a 1.5 MW wind turbine are carried out to assess low voltage ride-through performance of the proposed second-order sliding mode control strategy in case of unbalanced voltage sags.