适用于三电平逆变器的电流谐波最小脉宽调制策略

Current harmonic minimum pulse width modulation for three-level inverter

受限于散热条件,大功率牵引传动系统中逆变器开关频率通常很低,三电平逆变器由于在低开关频率下具有较小的输出谐波、较低的dv/dt等特点在中高压大功率领域中被广泛应用。以三电平中点钳位型逆变器为研究对象,提出一种电流谐波最小脉宽调制策略(CHMPWM),基于加权总谐波畸变最小的优化目标求解不同开关角个数下的开关角曲线,与目前应用较为广泛的特定次谐波消除脉宽调制进行谐波性能对比。该方法不会完全消除特定次数的谐波成分,但是总体电流谐波可以达到最小。针对电流谐波最小脉宽调制策略在实现过程中存在的困难,设计全速度范围基于电流谐波最小脉宽调制的多模式调制策略。仿真和实验结果表明,提出的调制策略具有良好的谐波性能,与理论分析结果一致。

Limited by the heat dissipation conditions,the switching frequency of inverters in high-power traction drive systems is usually very low.Three-level inverter topology is widely used in medium/highvoltage and high-power fields because of its small output harmonics and low dv/dt.Taking the three-level neutral-point-clamped inverter as the research object,a current harmonic minimum pulse width modulation(CHMPWM)was proposed.Based on the optimization objective of minimizing weighted total harmonic distortion,the switching angle curve under different number of switching angle were solved.The harmonic performance was compared with the selected harmonic elimination pulse width modulation,which is widely used at present.Although the modulation method proposed cannot eliminate specific harmonic,the overall current harmonic reaches the minimum.Aiming at the difficulties and problems in the implementation of CHMPWM,a multi-mode modulation strategy based on CHMPWM in full speed range was designed.Simulation and experimental results show that the proposed CHMPWM has good harmonic performance,which is consistent with the theoretical analysis results.