一种零矢量-变延时随机PWM方法

A Method of Zero Vector and Variable Delay Randomized PWM

随机开关频率脉宽调制方法在较宽频率范围可以获得均匀的频谱特性,但是由于数字化实现中采样周期同步随机变化,使得滤波器设计复杂,而且控制器的增益和调节器的设计需要随着采样频率的变化而变化,使得工程化实现困难。文中提出了一种新颖的双随机调制策略,将采样频率固定,采用变延时技术在一个采样周期内计算下一个脉冲输出的延时时间,两个输出脉冲之间的周期为随机开关周期。同时随机化零矢量,通过约束保证平均开关频率等于采样频率。分析和试验结果表明该方法仅仅通过软件实现,不用改变硬件设计和散热设计,通用性强、频谱特性好。

The uniform spectral characteristics are achieved in the whole frequency interval for the randomized switching frequency PWM method. However, the synchronous change of sample frequency and switching frequency makes the filter design complex, meanwhile the digital realization of engineering becomes difficult as the gain of controller and modulator vary with the sample frequency A novel strategy of dual randomized modulation is presented by which the sample frequency could keep unchanged. The delay time of next pulse output is calculated in current sampling interval with variable delay technique. The randomized switching period is formed with the interval of two output pulses. Zero vectors are randomized with the sample frequency and the average switching frequency equals to sample frequency with some constraint. Analysis and experiment indicate that the method has intensive commonality and good spectral characteristic, which can be realized only by software without modifying the hardware and radiating design,