不平衡电网下开关频率可控的双馈电机模型预测电流控制

Model Predictive Current Control of Doubly Fed Induction Generator with Controllable Switching Frequency under Unbalanced Grid

  • 摘要: 传统的有限状态集双馈电机模型预测电流控制在不同的工作点下具有变化的开关频率,不利于散热管理和滤波器设计。在模型预测电流控制的基础上,采用一个PI控制器可以实现目标函数中的权重系数自适应调节,使得开关频率可以跟踪参考值,在输出功率和转速变化时,开关频率能够保持恒定。此外在电网电压不平衡时,通过信号延迟法获取电网电压正负序分量并计算转子电流参考值的正负序分量,同时实现定子侧电流正弦对称和开关频率恒定的控制目标。在双馈电机平台开展试验并验证了所提方法的有效性,结果表明所提方法并不因开关频率的控制而牺牲稳态性能,并且开关频率能够在工作点变化以及不平衡电网下保持恒定,便于滤波器的设计。

     

    Abstract: The traditional finite-state-set model predictive current control has of doubly-fed induction generator different switching frequencies at different operating points, which is not conducive to heat dissipation management and filter design. On the basis of model predictive current control, a PI controller is adopted to adaptively adjust the weight coefficient in the objective function. So that the switching frequency can track the reference value, and the switching frequency can be kept constant when the output power and speed change. In addition, when the grid voltage is unbalanced, the positive and negative sequence components of the grid voltage are obtained by the signal delay method, and the positive and negative sequence components of the reference value of rotor current are calculated, and the control goals of sinusoidal symmetry of stator current and constant switching frequency are achieved at the same time. Experiments are carried out on the doubly-fed machine platform and the effectiveness of the proposed method is verified. The results show that the proposed method does not sacrifice the steady-state performance because of the control of switching frequency, and the switching frequency can be kept constant under the change of operating point and unbalanced power grid which is convenient for filter design.

     

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