复合Buck三电平直流变换器拓扑合成及其极低电压增益运行控制

Topology Synthesis of Hybrid Buck Three-Level Converter and Its Operation Control with Extreme Low Voltage-Gain

针对舰船直流区域配电系统的大比例降压需求,基于传统的单相二极管钳位型三电平逆变器拓扑,推导出两种准Buck三电平直流变换器。以两种准Buck三电平拓扑的"输入端并联—输出端串联"的合成方式,提出一种复合Buck三电平直流变换器。采用双调制波PWM控制方法,实现变换器无需变压器或耦合电感的极低电压增益运行,同时避免功率开关的极端占空比状态。根据电压增益和占空比所允许的范围,构建双调制度的约束函数,实现变换器功率开关的非极端占空比与电感电流波动幅度的协调控制。最后,通过两组典型的实验,表明了所提拓扑和控制方法的可行性和有效性。

In order to satisfy the high step-down conversion demand of the DC zonal electric distribution system on the ship, two quasi Buck three-level DC-DC converters are deduced based on the traditional single-phase diode-clamped three-level inverter. Then a novel hybrid Buck three-level converter is synthesized by the mode of the ＂input sides in parallel--output sides in series＂ of the two quasi converters. The double-wave PWM control method is adopted, and it can not only operate with transformerless extreme low Voltage-gain, but also avoid extreme duty cycles of the power switches. The restricted functions of the double-wave indexes are established by means of the given ranges of the voltage gains and duty cycles, then the harmonic control method for the non-extreme duty cycles and the fluctuating amplitude of the inductor current can be obtained. Finally, the feasibility and validity of the proposed topology and control method are verified by two groups of typical experiments.