Overshoot Dynamics in Parallel Connectivity Enabled Multilevel Converters: Generalized Analytic Expression and Impact Analysis
Multilevel converters are indispensable in power transmission and motor drivetrains, offering enhanced scalability and flexibility through parallel connectivity. This advancement offers beneficial features like sensorless voltage balancing and reduced impedance. However, parallel connectivity also poses challenges related to overshoot dynamics during the energy balancing process. Previous studies primarily examined energy loss, assuming paralleling intervals do not interfere with balancing processes. This research challenges this assumption, especially when paralleling intervals approach the energy exchange time constant. We present a generalized analytical model, accommodating scenarios where parallelization either does or does not interfere with energy exchange among paralleled submodules. Validation on an experimental prototype replicates both scenarios. Our analysis reveals varying thermal stress based on transistor type, with GaN HEMT experiencing over four times higher junction temperature fluctuations than Si and SiC MOSFET. Moreover, there is a heightened risk of voltage stress, with measured voltage overshoot 71.6% higher due to paralleling dynamics. These findings enable design of multilevel converters for robust performance in diverse applications.
