双向LLC谐振型直流变压器的软启动及功率换向控制

Control Scheme of Bidirectional LLC Resonant DC-DC Transformer for Soft Start and Power Conversion

双向LLC谐振型直流变压器(DCT)在保持了LLC谐振变换器高效率和高功率密度等优点的同时,具备双向传输能量的能力。通过对双向LLC谐振型DCT在变频控制和移相控制下增益特性曲线的分析,提出一种基于移相控制的软启动控制策略,使得DCT无论是空载还是满载启动,都能平稳快速地建立输出电压,有效避免了谐振网络中的电流和电压冲击。针对双向LLC谐振型DCT既可为负载供电又能接收能量回馈的工作特点,采用一种基于输出电容电压滞环控制的功率换向控制策略,可准确迅速地变换DCT的工作模式,从而顺利地改变功率流动方向。所提控制策略的可行性和有效性通过仿真和样机实验得到了验证。

Bidirectional LLC resonant DC-DC transformer(DCT) has the advantages as LLC resonant converter in achieving high efficiency and high power density. A new soft start control strategy based on phase shift control is proposed by the gain curves analysis of LLC resonant DCT under variable frequency control and phase shift control, which guarantees that there will be no current and voltage stress in the resonant tank during the soft start-up process. Meanwhile, the output voltage is built up quickly and smoothly. A bidirectional power conversion control strategy base on hysteresis control of output capacitor voltage is adopted for the characteristic of not only supplying power but also receiving energy feedback, which changes the direction of power flow smoothly. The performance of the proposed control scheme is verified by simulation and experimental results.