三电平PWM策略谐波性能的二重傅里叶分析

Double Fourier analysis of the three-level PWM harmonic performance

针对传统获取PWM环节输出谐波方法易受仿真步长、噪声、精度等影响,提出一种基于二重傅里叶积分的精确解析法,深入分析了三电平PWM的输出谐波性能.首先建立三电平变换器输出相桥臂电压的二重傅里叶方程;然后根据不同采样方式,引入对应的积分界限,解析分析其谐波成分.研究结果表明:不对称规则采样方式与对称规则采样相比,具有更好的谐波输出性能;三角载波调制时总谐波畸变率降低8.86%,空间矢量调制时能降低26.71%.理论推导与仿真结果对比分析表明,与常规FFT工具箱获取谐波畸变率相比,所提精确解析法能有效避免仿真误差、噪声等影响,具有更高的准确性.

In order to avoid the influence of simulation step size, noise and accuracy problems in the traditional approaches in＇getting the output harmonic performance of pulse width modula- tion （PWM）, using the double fourier integral proposed a novel analytic method to deeply ana- lyze the harmonic output performance of the three-level PWM strategy. After the double fou- rier equations of phase bridge voltage are established, this study introduced the different inte- gral boundaries in terms of the sampling mode. The results show that： the asymmetric sam- piing mode has better harmonic output performance in contrast with the symmetric one; when adopting the triangular carrier PWM, the THD of asymmetric regular sampled PWM reduces 8.86% compared with the symmetric one, and 26. 71% reduction when using space vector PWM. The theoretical derivation and simulation results indicate that, the proposed analytic so- lution can avoid the effect of simulation errors and noise, and obtain a better accuracy in com- parison with the method using FFT toolbox.