模块化多电平变换器与级联H桥变换器在中高压变频器应用中的对比研究

级联H桥型变换器CHB(cascaded H-Bridge)由于其笨重、复杂的多绕组移相变压器,限制了其向更高电压/功率等级电机驱动中应用。而模块化多电平变换器MMC(modular multilevel converter)的拓扑结构相比CHB可省去其笨重、复杂的移相变压器,因而更希望能够采用MMC来实现更紧凑、更灵活的电机驱动解决方案。但需要指出,MMC与CHB实际上存在很多不同之处,至今还没有文献对这两种拓扑各方面性能进行过系统的比较。为此,文中首次详细对比了MMC与CHB在电路结构、工作原理、元件数量、PWM调制方法、谐波性能等方面的优缺点,并探讨了MMC在电机驱动应用中需要面对的电容电压平衡问题、环流问题、启动预充电问题、以及低频运行时的电容电压波动等问题,并给出了相应的解决方法与一些基本的实验验证,旨在为模块化多电平换流器在电机驱动应用中的推广提供一点抛砖引玉的作用。

Comparative Study About Application of Modular Multilevel Converter and Cascaded H-bridge in Medium-high Voltage Converter

Cascaded H-bridge converter (Cascaded H-Bridge, CHB) due to its bulky, complex multi-phase-shifting transformer winding, limiting its application to a higher voltage and power level motor drives. The modular multilevel converter (Modular Multilevel Converter, MMC) eliminates the need for the complex phase-shifting transformer, so people began to want to use MMC to achieve a more compact, more flexible motor drive solution. It is necessary to emphasize that there are many differences of MMC and CHB, yet no one has made systematic comparison about them. This paper will firstly detail the merit and demerit of MMC and CHB in circuit structure, operating principles, quantity of components, PWM modulating methods, harmonic characteristics etc. Also, this paper will discuss the problem of voltage balance of the capacitor, the circulation, precharge, the voltage fluctuation when operating under low frequency etc.In the end, we will put forward our solutions against these problem with proper verification in order to draw more attention to the popularize of MMC in the field of motor drive.