Generalized Bidirectional Multilevel DC-DC Converter

In this paper, a novel generalized bidirectional multilevel DC-DC converter is introduced. The proposed converter is capable of high power conversion between low voltage (LV) and medium voltage (MV) levels by using uniform low-voltage half bridge IGBT module. Single source is applied at low voltage side and both single and multiple sources in series can be applied at high voltage side. The operating rules for bidirectional operation are introduced and switching states and sequences are analyzed. Simulation and experimental results of a 4-level hardware prototype is used as an example to validate the proposal. Importantly, the unbalancing issue is investigated. Small signal model and closed-loop control are developed to balance capacitor voltages. Simulation results is presented finally to testify the necessity and practicability of the proposed closed- loop control.