混合级联多电平变换器SHEPWM方法的仿真

研究了混合级联多电平变换器的特定谐波消除脉宽调制(SHEPWM)技术，针对1／4周期对称的混合级联多电平SHEPWM问题，提出了一种使用具有均匀电平的通用多电平SHEPWM方法求取预期的输出电压波形，然后采用混合级联多电平电路来实现所需电压和功率输出的解决办法。以两级混合级联多电平电路为例，对混合级联多电平逆变器的SHEPWM方法进行了仿真研究，结果证明：混合级联多电平SHEPWM非线性方程组形式和求解过程与通用的均匀电平多电平变换器一样简单，易于收敛；适用于通用均匀电平多电平变换器的SHEPWM非线性方程组求解问题的结论，完全适用于混合级联多电平变换器；直流母线电压利用率很高，电压调制比可以达到1．158；SHEPWM法的谐波消除效果非常理想，输出电压波形质量高，是混合级联多电平变换器的一种非常有效的控制策略。

RESEARCH OF SHEPWM TECHNIQUE FOR HYBRID CASCADE MULTILEVEL CONVERTERS

Selected harmonic elimination PWM (SHEPWM) technique applicable to hybrid cascade multilevel converter is studied. A solution is proposed by using generalized SHEPWM methods adopted in multilevel converter with equal input voltage-levels for establishing, solving nonlinear SHEPWM equations and using hybrid cascade multilevel topology to realize the anticipant output voltage waveform. Taking the example of two stage hybrid cascade multilevel converter, simulations of SHEPWM technique applicable to hybrid cascade multilevel voltage converter using POWERSIM 4.0 are carried out. The results demonstrate that conclusions reached from establishing and resolving of nonlinear SHEPWM equations applicable to multilevel converters with equal input voltage-levels are also applicable to hybrid cascade multilevel converters. The SHEPWM based method could make full use of DC-link voltage and provide high quality output. SHEPWM based method is a very effective control strategy applicable to hybrid cascade multilevel converters.