Topology and control strategy of module multiplexing power electronic transformer

Abstract

Multi-port power electronic transformer is the core equipment of AC/DC hybrid power grid and active distribution network. However, there are a large number of internal modules, including a large number of capacitors, high-frequency isolation transformers and other equipment, and the production cost is high. In response to its light weight requirement in engineering applications, this paper proposes a module multiplexing power electronic transformer (MM-PET). By dividing phase unit into upper, common and lower arms, and switching the arm multiplexing state via two arm switches, a quarter of the number of modules can be saved. The carrier phase shifted -nearest level segmented joint modulation strategy (CPS-NLM) and module capacitor voltage equalization strategy are designed to match the multiplexing topology. The simulation results based on PSCAD/EMTDC show that MM-PET can successfully complete capacitor voltage balancing and voltage conversion in the upper arm multiplexing mode and lower arm multiplexing mode respectively, effectively achieving the goal of lightweight.