三相软开关逆变器的PWM实现方法

该文详细阐述了采用三角载波和锯齿载波对本逆变器实现(ZVS)软开关动作的影响。使用三角载波实现软开关动作时，由于开关动作时刻不固定，使得谐振时刻难于控制，并且谐振次数多，使直流母线电压得不到充分利用。采用正斜率锯齿载波虽然能解决上述问题，但是会造成在锯齿波垂直沿前后处于零矢量状态，电机的能量与谐振电路不发生交换，不能满足软开关谐振条件。指出要实现本电路的软开关动作模式，载波必须采用正负斜率交替的锯齿波，并根据电机电流极性来切换锯齿波的斜率，这是逆变器开关元件实现软开关动作的必要条件。实验证明了采用本控制方式，逆变器的输出电流波形具有良好的正弦度。

A PWM REALIZATION METHOD FOR THREE-PHASE SOFT-SWITCHING INVERTER

The influence of triangular and saw-tooth carrier waves on the action of the soft-switching inverter is described. When the triangular carrier wave is used in the soft-switching action, not only the resonance-trigger time is difficultly controlled due to the unfixed switching time, but also the DC voltage utilization is insufficient due to many resonance times. Although the positive slope saw-tooth carrier can avoid these problems above mentioned, it brings zero vector states around the vertical edges where the energy cannot be exchanged between the motor and the resonance circuit and thus the condition of soft-switching resonance cannot be satisfied. The saw-tooth carrier wave, with alternate slopes (positive or negative) according to the motor current polarities to complete the action of the soft-switching PWM inverter is proposed. The results of experiments indicate that this control method can obtain near-sinusoidal output line current waveforms in the inverter.