基于随机脉宽调制技术简化中频电源输出滤波器

Output filter simplification based on random PWM for medium frequency power supply

在分析逆变器控制模型的基础上,将单极倍频和随机脉宽调制技术用于逆变器波形调制,有效提高逆变器等效开关频率,并明显降低开关频率处的离散谐波幅值。分析了随机信号对开关函数功率谱密度特性的影响,据此提出随机脉宽调制技术的实用化设计方法。改进后逆变器输出滤波器的截止频率可以取较高值,保证足够的控制系统带宽,有效提高逆变器输出电压波形质量。仿真和实验表明,开关频率处幅值较大的离散谐波扩展为一定带宽内幅值较小的连续谐波,谐波幅值大幅降低,结果验证理论分析的有效性。

Based on the analysis of electric inverter control model,the single-pole double-frequency PWM and the random PWM are used to modulate the inverter waveform,which improves the equivalent switching frequency of inverter and reduces the amplitude of discrete harmonics at switching frequency. The influence of random signals on the power spectral density characteristic of switching function is studied and a practical design of randomized PWM is proposed. The cut-off frequency of improved inverter output filter can be set higher to ensure the bandwidth of control system and improve the waveform quality of inverter output voltage. Simulation＇and experiment show that,the discrete harmonics with higher amplitude at switching frequency extend as the continuous harmonics with lower amplitude within a certain bandwidth, which verifies its effectiveness.