A Novel Variable Exponential Power Sliding Mode Observer for MMC

Modular multilevel converters are widely used due to large power density, high efficiency, and strong scalability. Thousands of submodules have led to an increasing number of capacitor voltage measurement devices, making the hardware structure complex, bulky, and expensive. This article proposes a variable exponential power sliding mode observer that can observe capacitor voltage and bridge arm current without any voltage measurement equipment, eliminating the inherent sliding mode chattering of traditional sliding mode observers under sudden changes in DC side voltage. It can also ensure a high degree of observation accuracy under parameter mismatch (capacitor preburning and inductance mismatch), proving the convergence law of observation errors. And through Simulink simulation and MMC hardware prototype construction, the effectiveness of the proposed observation technique was verified by comparing it with traditional power-exponential observers.