级联无刷双馈电机低压穿越分析和改进

LOW VOLTAGE RIDE THROUGH ANALYSIS AND IMPROVEMENT OF CASCADE BRUSHLESS DOUBLY-FED MACHINE

针对级联无刷双馈电机组机侧控制器，在任意mt坐标系的数学模型下，推导功率电机有功功率和无功功率方程，由此提出一种基于功率电机定子电压定向的直接功率控制方法。电网电压对称跌落下，分析控制电机定子电流和控制电机定子反电动势的暂态响应，应用比例积分谐振控制器来降低控制电机定子暂态电流脉动，提高系统的稳定性和机组低压穿越能力。仿真结果证明理论分析的正确性和改进方法的有效性。

As the increasing of the proportion of wind power capacity, a higher request is brought forward for the ability to operate without taking off the grid when the voltage drop occurs at the grid interconnection. Compared with the brush double-fed motor, the brushless doubly-fed machine cancels the slip rings and brushes that significantly reduces the maintenance cost and improves the reliability, showing broad prospect in wind turbine generation system. This paper deduces the active power and reactive power equation of cascade brushless doubly-fed machine （CBDFM） in arbitrary reference frame and then a stator-voltage-oriented direct power control scheme is proposed. During the symmetrical grid voltage dip, we analyze the transient response of control machine stator current and control machine stator electromotive force. According to the expression, proportion integral resonance control is presented to accelerate the damping rate of the transient control machine stator current, improving the stability of control system and guaranteeing the ability of low voltage ride though of CBDFM. Simulation results validate the accuracy of theoretical analysis and the effectiveness of the proposed control algorithm.