半桥-全桥子模块混合型MMC的换流阀损耗分析方法

Converter Valve Loss Analysis Based on Half Bridge-full Bridge Sub-module Hybrid MMC

随着架空线路在直流输电工程中的应用和多端直流电网的逐步建设,半桥-全桥子模块混合型模块化多电平换流器(modular multilevel converters,MMC)具有广阔的应用前景,其损耗计算也具有重要的工程意义。针对控制环节中加入二次环流抑制和三倍频电压注入的半桥-全桥子模块混合型MMC,对其工作原理和调制策略进行了阐述,对换流阀的损耗进行了分类并给出了计算方法:根据桥臂电流方向对通态损耗进行分段计算;根据桥臂电流方向和桥臂电压变化情况对开关损耗进行分段计算。在PSCAD/EMTDC中进行仿真,验证了采用的半桥-全桥子模块混合型MMC损耗分析方法的正确性。计算和仿真结果表明,半桥-全桥子模块混合型MMC的阀损耗和全桥子模块比例正相关,且受到功率因数角和调制比的影响,在允许范围内功率因数角越接近零损耗越低,调制比越高损耗越低。

With the application of overhead lines in DC transmission engineering and the gradual construction of multi-terminal DC power grids,the half bridge-full bridge sub-module hybrid modular multilevel converter(MMC)has a broad application prospect,with its loss calculation having great engineering significance.For the half bridge-full bridge sub-module hybrid MMC to be added into the control unit with the secondary circulation current suppression and the triple frequency voltage injection,its working principle and modulation strategies are described,and the loss of the converter valve is classified and the calculation method is given:the on-state loss is calculated in sections according to the current direction of the bridge arm;the switching loss is calculated in sections according to the current direction and the voltage variation of the bridge arm.The simulation in PSCAD/EMTDC verifies the correctness of the half bridge-full bridge sub-module hybrid MMC valve loss analysis.The calculation and simulation results show that the valve loss of the half bridge-full bridge sub-module hybrid MMC is positively correlated with the proportion of the full-bridge sub-modules,and is affected by the power factor Angle and the modulation ratio.That is,within the allowable range,the closer the power factor Angle is to zero,the lower the loss is;and the higher the modulation ratio,the lower the loss.