基于逆变器死区特性的永磁同步电动机系统的μ-修整变结构控制

μ-MODIFICATION VARIABLE STRUCTURE CONTROL OF PMSM SYSTEM BASED ON INVERTER DEAD-TIME

永磁同步电动机调速系统由PWM逆变器、永磁同步电动机和机械负载三部分组成,每个部分都具有非线性特性和参数的不确定性。因为PWM逆变器死区的存在,在低速以及调制频率很高时,死区特性将会导致逆变器的 输出电压包含很大的谐波分量,使得电机转矩发生很大的脉动,甚至导致系统的不稳定。有些学者采用变结构控制降低死区的影响,由于变结构控制本身具有抖振现象,这使得所设计的控制器在到达滑模平面之前很容易激起系统的未建模动态,导致系统无法克服逆变器死区的影响。该文采用具有“.修整项的自适应滑模变结构控制方法来降低抖振对永磁同步电动机系统的影响。设计两个参数,通过调节设计参数可以很容易控制抖振。该控制器对参数摄动和外部扰动具有很强的鲁棒性,控制器不但可以消除逆变器死区的影响,同时还可以使系统全局稳定并且达到准确的位置跟踪。最后利用MATLAB对整个系统进行了仿真,仿真结果证明该设计方案优于自适应变结构控制方法。

A PMSM drive system consists of a dc-ac inverter, PMSM and some mechanical load. All the three components of the system are characterized by models which are non-linear and contain unknown parameters. In the case of low speed and high regulation frequency, the dead-time characteristics of the PWM inverter may cause output voltage containing lots of harmonics, which introduces great ripples to its torque, and even make system unstable. By adaptive variable structure control method, variable structure control is applied to reduce the affects of dead-time. Due to chatting induced by variable structure control, the controller designed may cause system unmodeled dynamics before reaching the sliding surface. This paper makes use of adaptive variable structure control with μ-modification to reduce the chatting and eliminate the effects of inverter dead-time. We design two parameters to regulate the chatting introduced by variable structure control. We can control the chatting easily by regulate the designed parameters. The strategy presented in this paper possesses good robust performance to the variation of system parameters and out disturbances which not only can ensure accurate tracking performance but also achieves global stable. At last, we use MATLAB to simulate the whole system. The simulation results show that the strategy in this paper is better than the adaptive variable structure control method.