Development of very power converters for electric utility applications

对于大功率变换器系统，研究了双多电平电压变换器与谐波对消电抗器的耦合。双三电平变流器控制。特定谐波对消PWM技术可以在较低的开关频率下控制电压，产生更好的波形。纹波电压注入法。在直流链路中注入频率为电源线频率6倍的纹波电压，可以得到36步或48步的极低失真波形。一种新型六相电压源逆变器。纹波电压注入方法可以成功地应用于不使用单相变压器的六相逆变器，并且可以产生60步的近正弦波形。未来的问题。纹波电压注入电路中变压器的漏电感会对电压波形产生不利影响。因此，我们应该实现三相系统的无变压器注入电路。

For very high power converter systems, double multilevel voltage-source converters coupled with harmonic canceling reactors have been investigated.1.Control of double three-level converters.The specific harmonics canceling PWM technique can control the voltages at lower switching frequencies and can generate much better waveforms.2.Ripple voltage injection method.The injection of ripple voltages with a frequency of six-times that of power lines into the dc link has been proposed and it is shown that very low distortion waveforms with 36- or 48-step can be obtained.3.A novel six-phase voltage-source inverter.The ripple voltage injection method can successfully apply to a six-phase inverter without using a single-phase transformer and can produce nearly sinusoidal waveforms with 60-step.4.Future problems.The leakage inductances of the transformers in the ripple voltage injection circuit will cause an adverse effect on the voltage waveforms. Therefore, we should realize a transformerless injection circuit for three-phase systems.