基于电流谐波优化的混合脉宽调制策略

受轨道车辆牵引功率大、开关频率低的限制,牵引传动系统多采用低频区异步调制,基频以上单脉冲调制的脉宽调制方式,且在中频过渡区通常需采用优化同步调制以达到改善变流器输出特性的目的。电流谐波最小脉宽调制技术(CHMPWM)是优化同步调制的一种,它以电机电流谐波整体最优为目标进行调制,有助于高性能电流闭环控制的实现,近年来受到广泛关注。对基于电流谐波优化的混合脉宽调制策略展开研究,首先分析CHMPWM的开关角求解方法及不同开关角分布方式对其性能的影响,并从电流谐波、转矩脉动等方面与特定谐波消除脉宽调制技术(SHEPWM)进行对比;然后完成基于现场可编程门阵列(FPGA)构架的混合脉宽调制技术,并实现不同调制模式间的平滑过渡。最后对所提方法进行仿真和实验验证。

Hybrid Pulse Width Modulation Strategy Based on Current Harmonic Minimum Technique

In traction driving system, asynchronous modulation and single pulse modulation are often used in low and high frequency regions, while in medium region, in order to improve the quality of the output waveform, optimal synchronous modulation is necessary. Current harmonic minimum PWM (CHMPWM) is one of the optimal synchronous modulation methods. Because of its excellent harmonic performance of output current, CHMPWM is considered in special. In this paper, a hybrid pulse width modulation strategy on the basis of current harmonic optimization is proposed, by considering the solution of CHMPWM angles and the influence of different angle distributions on its performance. A comparison between CHMPWM and SHEPWM is carried out by considering current harmonics and torque pulsation. By use of FPGA design, the hybrid PWM modulation strategy is implemented. As a result, a smooth transition between different modulation methods is achieved, and the harmonics features of motor current in medium and high frequency regions are improved. Simulation and experimental results confirm the effectiveness and validity of the proposed scheme.