混合型MMC器件损耗分布与电容纹波电压综合优化方法

Comprehensive optimal method of device loss distribution and capacitor voltage ripple for hybrid modular multi-level converter

针对现有全桥-半桥混合型模块化多电平换流器(MMC)控制难以兼顾逆变工况下半桥子模块下部绝缘栅双极晶体管(简称半桥子模块中T2管)损耗降低与电容纹波电压抑制的问题,提出半桥子模块中T2管损耗降低及电容纹波电压抑制的综合优化方法。分析电容电荷对半桥子模块中T2管损耗及电容纹波电压的影响路径,指出半桥子模块中T2管通态损耗降低与电容纹波电压抑制间的矛盾。计及2倍频环流注入,分析模组解耦与主动旁路控制间的相互作用。考虑主动旁路控制降低半桥子模块中T2管损耗的优势及模组解耦控制抑制电容纹波电压的能力,提出模组平均开关函数及主动旁路半桥子模块个数的设计原则,并给出整体控制框图。在MATLAB/Simulink及PLECS中建立仿真模型,仿真结果表明:在调制比取0.827及单位功率因数下,相比主动旁路控制,所提方法可使半桥子模块中T2管损耗与电容纹波电压分别降低约20%和28%。

Conventional control strategies for hybrid modular multi-level converter(MMC)containing of halfbridge submodules(HBSMs)and full-bridge submodules(FBSMs)cannot achieve the loss reduction of the lower IGBT in HBSMs(i.e.,T2)under the inversion condition and capacitor voltage ripple suppression simultaneously.A comprehensive optimal method for reducing the loss of T2 in HBSMs and suppressing the capacitor voltage ripple is proposed.The effect path of the capacitor charge on the loss distribution of T2 in HBSMs and capacitor voltage ripple is analyzed.The contradiction between the conduction loss reduction of T2 and the voltage ripple suppression of capacitor in HBSM is elaborated.Based on the second harmonic circulating current injection,the interaction between module decoupling control and active bypass control is analyzed.Considering the advantages of active bypass control to reduce the loss of T2 in HBSM and the ability of module decoupling control to suppress capacitor voltage ripple,the design principle of module average switching function and actively bypassed HBSM number is proposed,together with the overall control block diagram.The simulation model is built in MATLAB/Simulink and PLECS,and the simulative results show that when the modulation index is 0.827 and unity power factor is adopted,compared with the active bypass control,the proposed method can reduce total loss of T2 in HBSMs and capacitor voltage ripple voltage by about 20%and 28%respectively.