基于预设载波的随机开关频率调制方法

现有的随机开关频率调制方法未考虑载波切换频率与载波频率间的关系,因此会使逆变器输出交流电产生一定的谐波畸变.为了克服这一不足,通过分析载波切换频率对随机载波信号的影响,得出预置载波随机切换时,前后两条载波的相位不匹配是造成逆变器输出电压产生畸变的根本原因,并提出采用随机切换预设载波的方法实现开关频率的随机化.仿真及实验结果表明,随机脉冲宽度调制(PWM,Pulse Width Modulation)方法不但可以有效抑制输出电压的高次谐波而且在波形正弦度方面优于常规随机PWM方法.

Random PWM method based on pre-determined carrier frequencies

For reported random frequency pulse width modulation(PWM) methods, harmonic distortion appears in the output waveform because the relationship between the carrier frequencies and their changing frequency is not carefully considered. To cope with the above obstacle, the effect of carrier changing frequency on the randomized carrier signals was investigated. A fact that phase mismatch of the two changing carrier signals induces the output voltage distortion was subsequently obtained. Then, a proposed approach was to select the switching frequency randomly among a few pre-determined carrier frequencies. Both simulation and experimental results verify that using the proposed PWM technique, the dominant harmonic clusters are effectively reduced while retaining good sinusoidal output waveforms, which are superior to that based on the conventional random PWM methods.