In high power traction drive system, traction motor usually operates under square wave mode in the field-weakening area. The traditional vector control under the square wave mode is limited by the single control freedom degree. Meanwhile, accurate field orientation is affected by the rotor time constant. Therefore, the accurate field-oriented control under the square wave mode is the key to the high performance control of the traction motor in the field-weakening area. This paper proposes a single current loop control strategy for the square wave mode. Q-axis voltage is calculated from the d-axis voltage and the maximum output voltage of inverter. The influence of the motor parameters on the output torque, flux linkage, current and voltage of the square wave mode is deduced by the motor equation, and then the parameter robustness of the proposed control strategy is analyzed. The simulation and experimental results show that the proposed method can realize the fast and precise control of the motor current, and accurate field orientation can be achieved to ensure that the motor outputs the desired torque.%在轨道牵引传动系统中,电机在弱磁区通常采用方波控制.方波下传统矢量控制算法受限于电压角度这一单自由度而失效.同时,电机控制中磁场定向的准确与否受电机参数变化的影响.因此,方波下准确的磁场定向控制是牵引电机在弱磁区高性能控制的关键.该文针对方波特殊工况,提出一种单电流闭环弱磁控制策略,方波下电机q轴电压指令通过d轴电压指令和逆变器可输出最大电压得到.利用电机方程推导得到方波下电机参数变化对电机输出转矩、磁链、电流和电压的影响,进而分析了所提方波控制策略的参数鲁棒性.仿真和实验结果表明,该方法可实现对电机电流快速精准地控制,能够对因电机参数变化引起的磁场定向不准进行校正,保证电机输出期望转矩.
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