The development and integration of renewable energy sources have gained significant attention over the past few decades. It provides a means to cope with the increasing energy consumption demand while reducing carbon emissions. Voltage-source-converter-based high voltage direct current (VSC-HVDC) transmission is a critical enabling technology in integrating hydroelectric power, wind-power plants, and photovoltaic systems into the power grid. To further reduce converter losses and converter station footprint, VSC-HVDC systems have evolved in the past twenty years from the traditional two- and three-level converters to multilevel converters. The modular multilevel converter (MMC) is well-known for its higher modularity, reduced harmonics, and improved converter efficiency, compared to the traditional two- and three-level converters. Recent advancements in VSC-HVDC have brought a new class of multilevel converter topologies, i.e., the so-called hybrid cascaded multilevel converters (HCMCs), which combine the reduced footprint of the conventional VSCs with the lower losses and reduced output harmonics of the MMC. However, simulating large-scale AC-DC networks introduced significant computational challenges in electromagnetic transient (EMT) type programs, as a large number of switching operations and massive input/output data transfer are simulated at a small time step. Thus, the large number of series-connected submodules introduce a high dimension, time-variant matrix to be solved at each time step. Therefore, the efficiency of DM is limited in the electromagnetic transient (EMT) type simulators. This thesis focuses on developing new numerically efficient models, which improve the simulation speed and maintain simulation accuracy for system-level studies simultaneously. The proposed models in this thesis present different levels of simulation details and efficiency, which offer great flexibility to accommodate the requirements of various study tasks. Different from the prior-art models, which mainly focus on the MMC topology, the numerically efficient models of hybrid multilevel converters and their real-time simulation methods are investigated in this thesis.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat
