Variable-pitch control is an effective technique for ensuring the constant-power operation of wind turbines over the range of rated wind speeds.The frequent and strong action of a pitch actuator increases the mechanical fatigue load of wind turbines,affects the output quality of the generator,and reduces the service life of wind turbines.Most cur-rent switching methods switch only at a certain threshold,which causes switch oscillation.To address these issues,we propose a multi-mode soft switching variable-pitch control strategy based on Takagi-Sugeno(T-S)fuzzy weighting.In this method,intelligent and traditional controls are combined,based on the deviation of the real-time rotation speed of the generator from its rated rotation speed and the change rate of the real-time rotation speed.T-S fuzzy inference is also utilized to achieve a smooth transition in the output of the multi-mode controller by the use of fuzzy control,fuzzy ad-aptive proportional-integral-derivative control,and proportional-integral control to realize a soft switch.This method simultaneously employs the advantages of three kinds of control methods and solves the switch oscillation problem.In this study,we built a multi-mode soft-switch control model to address the variable pitch of permanent-magnet direct-drive wind turbines.The simulation results show that this method exhibits the advantages of the three control methods,overcomes switch oscillation,slows frequent action of the actuator,smooths the adjustment of the pitch angle,improves the precision of the output power,and reduces fluctuation.%变桨控制是确保风电机组在额定风速以上恒功率运行的一种有效的控制方式.变桨控制执行机构的动作频繁且幅度较大,增加了风电机组各部分的机械疲劳载荷,影响发电机的输出电能质量和机组的使用寿命;现有的切换控制方法多数只在某一阈值进行切换,导致切换振荡.针对上述问题,提出了基于T-S型模糊加权的多模软切换变桨控制策略,该方法将智能控制与传统控制相结合,根据风电机组发电机的实时转速与其额定转速的偏差及其变化率,利用T-S型模糊推理,完成基于模糊控制、模糊自适应PID控制和PI控制的多模控制器输出的平滑过渡,实现软切换,其优点是兼顾3种控制方法的优势,解决了切换振荡问题.搭建了永磁直驱风力发电机组变桨的多模软切换控制的仿真模型.仿真结果表明,此方法展现了3种控制方法的优点,克服了切换振荡,减缓了执行机构的频繁动作,使桨距角调节更加平滑,输出功率精度更高,脉动更小.
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