A Robust Control for D-STATCOM Under Variations of DC-Link Capacitance

DC-link capacitors are among the most sensitive components in the power electronic converters since they are vulnerable to abrupt failures and capacitance variations. These variations stem from aging, cell failure, and fuse failure in the parts of the capacitor bank. Such changes decline the performance of control loops and prompt to increase the harmonics at point of common coupling and ripples in the dc-link voltage. This article models all variations as uncertainties in the converter model and proposes a sliding-mode method to control the system. To examine the efficiency of the proposed controller for power electronic converters, a D-STATCOM, as a sensitive converter to its dc-link capacitance, is designed and constructed and tested under different reactive power compensating scenarios. Simulations and experimental results show that the proposed SMC-based controller properly controls the system under dc-link capacitance variations and improve the system reliability and the stability margin, while the performance of the conventional controllers influentially degrades in the presence of these uncertainties.