考虑异质器件混用与输出电平倍增的混合型MMC及其调控方法

Hybrid Modular Multilevel Converter Considering Heterogeneous Device Mixing and Output Level Doubling and Its Regulation Method

首先,为提高模块化多电平换流器(MMC)输出波形质量、降低装置运行损耗,提出一种基于Si和SiC器件组合应用的混合型模块化多电平变换器(HMMC)拓扑结构。该拓扑每个桥臂包含N个Si绝缘栅双极晶体管(IGBT)器件的半桥子模块,每相交流侧串联一个直流侧电压为半桥子模块一半的SiC金属-氧化物半导体场效应晶体管(MOSFET)全桥子模块,整体经济性较好。其次,提出一种面向输出电平数倍增的HMMC高、低频混合调制策略,并充分发挥SiC MOSFET开关损耗低的优势,在减小HMMC输出谐波的同时降低整体运行损耗。此外,分析混合调制策略下HMMC异质子模块直流侧能量的波动规律,提出一种高、低频模块直流侧电压稳定控制策略。最后,仿真和实验验证了所提HMMC拓扑结构和调制策略的可行性,并将所提HMMC、基于单一器件MMC和现有HMMC在损耗和成本方面进行综合对比,证明了该方案在降低损耗和减小成本方面优势显著。

First,in order to improve the output waveform quality of modular multilevel converter(MMC) and reduce the operation loss of the device,this paper proposes a hybrid modular multilevel converter(HMMC) topology based on the combined application of Si and SiC devices.Each bridge arm of the topology contains N half-bridge sub-modules based on Si insulate-gate bipolar transistor(IGBT) devices.And a full-bridge sub-module based on SiC metal-oxide-semiconductor field-effect transistor(MOSFET) whose DC-side voltage is half that of the half-bridge sub-module is connected in series on the AC side of each phase.The overall economy is good.Then,a high-frequency and low-frequency hybrid modulation strategy of HMMC for output level doubling is proposed,and the advantage of low switching loss of SiC MOSFET is fully utilized,which reduces the output harmonics of HMMC and reduces the overall operation loss.In addition,the fluctuation rule of the DC-side energy of the HMMC heterogeneous sub-module under the hybrid modulation strategy is analyzed,and a DC-side voltage stability control strategy for high-frequency and low-frequency modules is proposed.Finally,the feasibility of the proposed HMMC topology and modulation strategy is verified by simulation and experiment.The proposed HMMC,the MMC based on a single device and the existing HMMC are comprehensively compared in terms of loss and cost,which proves that the strategy has significant advantages in reducing loss and cost.