中点箝位型三电平变换器SHEPWM方法研究

Research on SHEPWM of Neutral-Point Clamped Three-Level Inverter

简单介绍了中点箝位型三电平变换器SHEPWM的原理,基于M ATLAB的FSOLVE函数解SHEPWM超越方程的方法,绘出了当超越方程个数N=11时的解轨迹曲线,从曲线上分析SHEPWM方法最大调制比可以达到1.15。为了验证上述解轨迹曲线的正确性和研究中点箝位型三电平变换器SHEPWM方法在不同调制比下的实际消谐波效果和相线电压谐波畸变,用M ATLAB的S IMUL INK图形化工具GU I仿真了各调制比下N=11时候相线电压的谐波畸变,并绘出了相线电压的消谐波效果和输出的相线电压和调制比关系曲线,得知随着调制比增大,实际的消谐波效果越来越好、输出相线电压的谐波畸变率THD也呈快速下降趋势。最后建立了三电平变换器的实验模型,用实验室开发的电力电子数控开发平台控制异步电动机的变频调速。实验结果与仿真结果一致,证实了FSOLVE函数求解的正确性和DSP数控系统控制电机调速的方便性。

Firstly, this paper introduces the principle of SHEWPWM technique for neutral-point clamped three-level inverter, and then a scheme using the function FSOLVE of Matlab is presented to solve the nonlinear equations of SHEPWM, the curve of the solution when N= 11 is obtained simultaneously. According to the curve, it is indicated that the maximal modulation ratio of SHEPWM technique can reach as high as 1.15. The THD of both phase voltage and line voltage with various modulation ratios when N=11 is obtained by Matlab/Simulink, which is used to verify the correctness of the curve and analyze the harmonic elimination effect of SHEPWM for neutral-point clamped three-level inverter. The relationship of phase/llne voltage THD and modulation ratio shows that the effect of harmonic elimination improves and the THD of output voltage declines with the modulation ratio increasing. At last, experiments as well as simulation are performed respectively and intercompared, and the results prove the correctness of the scheme.