基于逆变器死区特性的永磁同步电动机系统的自适应变结构控制

ADAPTIVE 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 ;同时PWM逆变器因死区的存在 ,在低速以及调制频率很高时 ,死区特性将会导致逆变器输出电压含有很大的谐波分量 ,使转矩发生很大的脉动 ,甚至可能导致系统不稳定。采用自适应变结构控制策略消除逆变死区的影响。首先详细分析逆变器死区的特性 ,建立死区的数学模型和整个系统的非线性模型 ,在死区模型中 ,给出变化和影响系统性能的参数 ;根据模型的特点 ,采用自适应滑模变结构控制算法 ,实现死区补偿和非线性控制 ,这种方法不需要测量死区的参数 ,具有较强的鲁棒性 ,可使系统全局稳定并且达到准确的位置跟踪。对所提出自适应律和滑模控制方法 ,利用Lyapunov稳定性理论 ,证明了系统的稳定性和收敛性。利用MATLAB进行了系统仿真 。

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 makes the system unstable. The paper applies the adaptive variable structure control strategy to eliminate the effects of the dead time of the PWM inverter. In this paper, the characteristics of the dead time of the PWM inverter are analyzed, and its mathematic model and the nonlinear model of the whole system are established. In the model of the dead time of the PWM inverter, the parameters which varies and affects the performance of the system are presented. Then based on the characteristics of the models, this paper makes use of adaptive variable structure control to realize the dead time compensation and the nonlinear control. The strategy presented in this paper possesses good performance in robustness while doesn't require the parameters of the dead time. It not only ensure accurate tracking performance but also achieves global stable. Furthermore, for the adaptive law and the sliding mode control strategy presented in this paper, this paper also proves the stability and convergence of the system applying Lyapunov theory of stability. At last, the system is simulated using MATLAB and the simulation results prove the effectiveness and feasibility of the strategy presented.