Advanced modulation, control and application for multilevel inverters.

摘要

The purpose of the research has been to develop advanced modulation, control and application for multilevel inverters. A new series of modulations has been proposed to achieve minimal THD (Total Harmonic Distortion) for multilevel inverters. The first minimal THD modulation is a real-time algorithm used to calculate optimal values of switching angles for given DC voltages and a modulation index. The second one is an algorithm used to calculate optimal values of DC voltages and switching angles for a given modulation index. The third one used an algorithm to calculate optimal values of DC voltages, switching angles and a modulation index. Another new optimal combination modulation strategy has been proposed for the 10 MVA 5-level cascade multilevel inverter based STATCOM (Static Synchronous Compensator) system. In this thesis, I also proposed several advanced controls for cascade multilevel inverters to be used in STATCOM applications. A new feedback control strategy for balancing individual DC capacitor voltages is proposed. The key part of the control strategy is a compensator used to cancel the variable parts in the model. I have also proposed the solutions for enhancing ride-through capability of the STATCOM during faults conditions.