多电平PWM逆变电路谐波分析与输出滤波器设计

在中压大容量变频驱动装置中，为解决电力电子器件耐压问题，基于PWM控制的多电平逆变技术得到广泛应用。这种中压变频器输出电压为多电平PWM脉冲波形，目前对其谐波还没有完善的理论分析。为避免高次谐波对电机的影响，有些用户要求为变频器设置输出滤波器。由于中压变频器容量较大，为滤波器设计带来一些新的问题。该文在大量仿真数据的基础上，总结出多电平PWM波形的谐波特点，为滤波器设计提供了理论依据。以此为基础，综合考虑基波压降、有功损耗、电流谐波和谐振等问题，推导出适合于中压大功率变频器输出5滤波器参数选取的简化公式，并通过实验予以验证。

HARMONIC ANALYSIS AND OUTPUT FILTER DESIGN FOR MULTILEVEL PWM INVERTERS

In order to resolve the voltage sustaining capability problem of power electronic devices, multilevel inversion techniques based on PWM control are widely spread in medium-voltage and large-capability Adjustable-Speed Drives (ASDs). Output voltage of this type ASD is multilevel PWM waveform, and by now there is not perfect theoretical analysis for its harmonics. To avoid the influence of high-order harmonics on motors, some users require output filter for medium-voltage ASDs. Due to the large capability of medium-voltage ASD, some new problems have to be considered. The frequency spectrum characters of multilevel PWM waves are concluded through lots of simulation results. It offers some academic fundamentals for the filter design. On this basis and considering some problems synthetically such as fundamental voltage loss, active power loss, current harmonics and resonance, this paper presents the parameter choice formulae that can be applied to medium-voltage and large-capability ASDs output filter design. The filter design in this way has been validated by experiments.