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 trajectory 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 performance 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.
[1] Geyer T, Papafotiou G, Morari M. Model predictive direct torque control—part I: concept, algorithm and analysis [J]. IEEE Transactions on Industrial Electronics, 2009, 56(6): 1894-1905.
[2] Geyer T. Model predictive direct current control: formulation of the stator current bounds and the concept of the switching horizon [J]. IEEE Industry Applications Magazine, 2012, 18(2): 47-59.
[3] Holtz J, Oikonomou N. Synchronous optimal pulsewidth modulation and stator flux trajectory control for medium-voltage drives [J]. IEEE Transactions on Industry Applications, 2007, 43(2): 600-608.
[4] Oikonomou N, Holtz J. Closed-loop control of medium-voltage drives operated with synchronous optimal pulsewidth modulation [J]. IEEE Transactions on Industry Applications, 2008, 44(1): 115-123.
[5] Holtz J, Oikonomou N. Fast dynamic control of medium voltage drives operating at very low switching frequency—an overview [J]. IEEE Transactions on Industrial Electronics, 2008, 55(3): 1005-1013.
[6] Holtz J, Qi X. Optimal control of medium-voltage drives—an overview [J]. IEEE Transactions on Industrial Electronics, 2013, 60(12): 5472-5481.
[7] Geyer T. A comparison of control and modulation schemes for medium-voltage drives: emerging predictive control concepts versus PWM-based schemes [J]. IEEE Transactions on
Industry Applications, 2011, 47(3): 1380-1389.
[8] 孙大南. 地铁车辆牵引电驱动系统控制关键技术研究[D]. 北京: 北京交通大学, 2012.
[9] Holtz J, Beyer B. The trajectory tracking approach—a new method for minimum distortion PWM in dynamic high-power drives [J]. IEEE Transactions on Industry Applications, 1994, 30(4): 1048-1057.
[10] Holtz J, Beyer B. Fast current trajectory tracking control based on synchronous optimal pulsewidth modulation [J]. IEEE Transactions on Industry Applications, 1995, 31(5): 1110-
1120.
[11] 马小亮. 概述低开关频率PWM变频的问题及解决办法[J]. 电气传动, 2009, 39(5): 3-9.
[12] 马小亮. 低开关频率中压传动的定子磁链轨迹跟踪控制综述[J]. 变频器世界, 2009, 12: 45-51.
[13] 符晓. 电励磁同步电机低开关频率控制技术研究[D]. 徐州: 中国矿业大学, 2011.
[14] 费万民, 张艳莉, 阮新波, 等. 三电平逆变器SHEPWM 非线性方程组的求解[J]. 中国电机工程学报, 2008, 28(6): 62-68.
[15] Holtz J, Oikonomou N. Estimation of the fundamental current in low-switching-frequency high dynamic medium-voltage drives [J]. IEEE Transactions on Industry Applications, 2008, 44(5): 1597-1605.
