基于定子磁链轨迹跟踪的优化PWM高性能闭环控制

High performance close-loop control of optimal PWM based on stator flux trajectory tracking

在低开关频率下采用优化脉冲宽度调制(pulse width modulation,PWM)可获得较小的谐波畸变,但将其直接应用于高性能闭环控制系统时会引起PWM波形紊乱和系统过流.给出了一组离线求解得到的特定谐波消除脉宽调制(selected harmonic eliminated pulse width modulation,SHEPWM)开关角,分析了将优化PWM应用于高性能闭环控制系统会造成系统过流的原因.深入研究了基于定子磁链轨迹跟踪的优化PWM闭环控制方案,给出了一种结合SHEPWM特点的脉冲实时修正策略,实现了采用优化PWM的磁链轨迹跟踪高性能控制.通过三电平逆变器异步电机驱动系统的仿真实验验证了该策略的有效性.结果表明,驱动系统在200～300 Hz的低开关频率下获得了较小的电流谐波畸变,同时具有快速动态响应能力.

Lower harmonic distortion at low switching frequency requires optimal pulse patterns. But it cannot be directly used in high performance systems. A stator flux tra- jectory tracking control （FTTC） system is studied, and a pulse width modulation （PWM） correction method is proposed. Based on this method, dynamic modulation errors and high overcurrents as the operating conditions change are discussed. Furthermore, high perfor- mance closed-loop control of optimal PWM based on FTTC with a self-controlled machine model can be realized. Simulation results show that both fast dynamic response and low harmonics characteristic can be achieved at a low switching frequency of 200-300 Hz. Its harmonic characteristic is more outstanding than that of model predictive direct control methods.