Power converter suitable for very high-power applications

提出了一种新型的三相多电平电压变换器。该变换器工作在低开关频率下，产生18阶电压，总谐波失真（T.H.D.）为10.7%。该变换器由一个中性点箝位（NPC）三相变换器和一个附加的单相NPC变换器组成。主三相变流器工作在一个电力线频率，即50赫兹或60赫兹，和附加的单相变流器工作在三倍的电力线频率，即150赫兹或180赫兹。使用所提出的转换器的双转换器系统产生36步电压，t.h.d.为5.1%，四倍转换器系统产生72步电压，t.h.d.为2.6%。提出了一种简化的双变换器系统，其中两个主变换器共用一个额外的单相变换器，即省略一个单相变换器。理论和实验结果表明，所提出的变换器具有优良的性能，适用于非常大功率的应用。

A novel three-phase multilevel voltage converter has been proposed. The converter operates at low switching frequencies and produces 18-step voltages with the total harmonic distortion (T.H.D.) of 10.7%. The converter consists of a neutral-point-clamped (NPC) three-phase converter and an additional single-phase NPC converter. The main three-phase converter operates at a power line frequency, i.e.50 Hz or 60 Hz, and the additional Single-phase converter operates at three times the power line frequency, i.e.150 Hz or 180 Hz. A double converter system using the proposed converters generates 36-step voltages with T.H.D.of 5.1% and a quadruple system generates 72-step voltages with T.H.D.of 2.6%.A simplified double converter system has been proposed, in which the two main converters share with one additional single-phase converter, i.e.one single-phase converter is omitted.The theoretical and experimental results showed that the proposed converters have excellent performance and are suitable for very high-power applocations.