基于特定谐波消除的多电平变换器最优基频调制

The selective harmonic elimination based optimal fundamental frequency modulation for multilevel converter

本文研究多开关模式下多电平变换器基频调制的优化问题。针对传统阶梯波调制只在部分调制比区间有解的局限,将阶梯波开关模式扩展为一般开关模式,利用Groebner基方法在全调制比范围内对各开关模式的消谐方程组进行求解,给出每种开关模式所能实现的调制比范围及开关角度的完全解;通过评价THD的大小,得到全调制比范围内的最优开关模式及相应的开关角度。实验结果验证了求解结果的正确性。

The selective harmonic elimination(SHE) based staircase modulation is a commonly used fundamental frequency modulation strategy for multilevel converters. However,the solutions to the staircase SHE equations cannot cover the full range of modulation index,which limits the applications of this modulation method. In order to solve this problem,this paper extends the staircase switching pattern to the general switching patterns,in which,the Groebner bases method is used to solve the SHE equations,and the achievable range of modulation index and the complete solutions for each switching patterns are obtained. By evaluating the total harmonic distortion,the optimal switching pattern and the corresponding optimal switching angles can be identified for the modulation indices in full range. Experiment results verify the correctness of the proposed method.