Jian Liu - Flying Capacitor Hybrid Mod Multilevel Converter

Title: Flying Capacitor Hybrid Modular Multilevel Converter with Reduced Number of Submodules and Power Losses

Presenter: Jian Liu was selected as the best presenter in the Test Bay area during the Lab Dialogue Session at the 2023 CPES Annual Conference.

Major Professor: Dong Dong

Abstract: This project introduces a new type of converter, called the flying capacitor hybrid modular multilevel converter (FC-HMMC), which offers an innovative alternative to traditional modular multilevel converters (MMC) for medium voltage (MV) applications. By combining the high voltage line frequency switches with the low voltage high frequency submodule (SM) based chain-link, the proposed hybrid solution can balance the benefits of conventional multilevel converters and MMCs. Compared to the HB-MMC, the FC-HMMC can save up to 50% of SMs, 25% of devices, 37% of capacitors, and 20% of conduction losses, resulting in significant improvements in power density and efficiency. Additionally, this topology allows for a decoupling of the DC and AC sides, which means that the modulation index is not fixed. Furthermore, the high voltage switch operates in soft-switching naturally at any modulation index or power factor, thereby reducing power losses. Finally, we validate the feasibility of the proposed topology through both simulations and experiments.