一种改进的异步电机模型预测直接转矩控制方法

Improved model predictive direct torque control for asynchronous machine

提出一种改进的模型预测直接转矩控制方法,通过磁链和转矩方程设计出一种优化矢量选择器,能够根据转矩和定子磁链的给定值得到给定的电压矢量.该方法只需对给定电压矢量所在扇区的3个电压矢量进行价值函数评估,使得在线优化计算量得到有效降低.针对由控制延时导致的定子电流在参考值附近振荡并增加电流纹波和转矩脉动,采用延时补偿提高了控制系统的性能.通过在模型预测直接转矩控制的价值函数中加入开关切换次数约束,能够在兼顾转矩和磁链偏差的同时进一步降低逆变器开关频率.最后,通过仿真和实验验证了所提出方法的有效性和可行性.

This paper proposes an improved model predictive direct torque control(MPDTC)method.An optimal voltage vector selector is obtained by analyzing relationship between stator flux and torque,which can be used to calculate the desired voltage vector based on the stator flux and torque reference.The method only needs to evaluate three voltage vectors in a sector of the desired voltage vector.As a result,the computational burden of conventional MPDTC is reduced effectively.Time delay introduced in computation can cause the stator current to oscillate around its reference and increase current and torque ripples.To solve the problem,a delay compensation method is used.Furthermore,switching frequency of the inverter is reduced significantly by introducing a constraint of power semiconductors switching number to the cost function of MPDTC.Both simulation and experimental results are presented to verify validity and feasibility of the proposed method.