基于龙伯格观测器的MMC子模块故障检测方法

模块化多电平换流器(modular multilevel converter, MMC)由大量子模块(submodule, SM)串联构成，是高压大功率领域最有发展潜力的变换器之一。SM功率开关开路故障和短路故障严重影响了MMC的可靠性，给MMC稳定运行带了巨大挑战。因此，为了快速地检测出故障SM,文中提出一种基于龙伯格观测器的SM功率开关故障检测方法。首先，分析SM故障特性，根据SM电容电压变化的数学关系，建立龙伯格观测器模型；然后，通过龙伯格观测器计算SM电容电压估计值，比较电容电压估计值与测量值，实现SM功率开关故障检测；最后，在PSCAD/EMTDC中搭建MMC系统仿真平台，并在实验室搭建MMC实验平台进行验证。仿真和实验结果表明，龙伯格观测器能够准确有效地检测出SM开路故障和短路故障，验证了该故障检测方法的可行性与有效性，但要对每个SM进行监测。

Fault detection method for modular multilevel converters based on Luenberger observer

Modular multilevel converter (MMC),which is composed of a large number of submodules (SM) connected in series, is one of the most promising converters in high voltage field. The open-circuit fault and short-circuit fault of the SM''s power switch seriously affect the reliability of the MMC,and it brings great challenges to the stable operation of the MMC. Therefore,in order to quickly detect the faulty SM,a fault detection method of the SM''s power switch in the MMC based on Luenberger observer is proposed. Firstly,the fault characteristic of the SM is analyzed,and the model of Luenberger observer is established according to the mathematical relation of the SM capacitor voltage change. Then,the estimated capacitor voltage is calculated by Luenberger observer,and the detection of the power switch fault is realized by comparing the estimated capacitor voltage and the measured capacitor voltage. Finally,the simulation model of the MMC system based on the PSCAD/EMTDC and the experiment platform in the laboratory are respectively built. The simulation and experiment results show that the open-circuit and short-circuit fault of the SM can be detected correctly and effectively,which verifies the validity and feasibility of the proposed method,but each SM needs to be monitored.