混合控制全桥+LLC+谐振变换器的优化设计

中图分类号TM461 论文编号1028703 13-S138 学科分类号080804

硕士学位论文

混合控制全桥LLC谐振变换器的

优化设计

研究生姓名 潘志杰

学科、专业 电力电子与电力传动

研究方向 功率电子变换技术

指导教师 阮新波 教授

南京航空航天大学

研究生院 自动化学院

二О一三年三月

Nanjing University of Aeronautics and Astronautics

The Graduate School

College of Automation Engineering

Optimization of Hybrid Controlled

Full-Bridge LLC Resonant Converter

A Thesis in

Electrical Engineering

by

Pan Zhijie

Advised by

Professor Ruan Xinbo

Submitted in Partial Fulfillment

of the Requirements

for the Degree of

Master of Engineering

March, 2013

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南京航空航天大学硕士学位论文

摘 要

在新能源分布式发电系统中，新能源发电单元受气候和天气影响很大，输出电压范围较宽。为了给后级变换器提供稳定的直流电压母线，需要在发电单元与后级变换器之间加入一个单向DC/DC变换器。全桥LLC谐振变换器可以在全负载范围内实现开关管的零电压开关和副边整流二极管的零电流开关，是该单向DC/DC变换器的可选拓扑之一。本文研究全桥LLC谐振变换器的优化设计。

全桥LLC谐振变换器即可采用变频控制又可采用定频控制，两种控制策略各有优缺点。混合控制策略将变频和移相两种控制方式进行了有机结合，输入电压较低时采用变频控制，输入电压较高时采用移相控制，解决了单种控制方式下变换器在宽输入电压范围内效率难以优化的问题。本文首先介绍变换器在变频控制和移相控制两种模式下的工作原理，利用时域分析法分析了两种模式下的电压增益特性。为使变换器在整个输入电压范围内实现高的变换效率，本文从损耗最小化角度出发，结合基波近似简化法,分析了控制模式切换点和谐振网络参数对变换器的影响，并给出一套优化设计方案。本文给出混合控制的电路实现和设计，并利用仿真手段得到该变换器的小信号幅频和相频特性，并给出闭环补偿网络的设计方法。

最后，制作了两台3kW原理样机，分别采用混合控制和全变频控制，对不同控制方式下的变换效率进行对比。实验结果表明，在宽输入电压的应用场合，混合控制比全变频控制具有更优的效率曲线。

关键词：LLC谐振变换器，变频控制，脉宽调制，混合控制，小信号特性

I

混合控制全桥LLC谐振变换器的优化研究

ABSTRACT

In distributed power generation system, renewable energy generation units are strongly dependent on the climates and weather, and thus the output voltage of these units has a wide variation range. In order to provide a stable dc voltage for the downstream converters, a dc-dc converter is necessary to interface the renewable energy generation units and the downstream converters. The full-bridge LLC resonant converter has the advantages of achieving zero-voltage-switching for all the power switches and zero-current-switching for the output rectifier diodes in the whole load range, and it is a promosing topology for the interfaced dc-dc converter. This thesis is dedicated to optimization of the full-bridge LLC resonant converter to achieve a high efficiency over the entire wide input voltage range.

The full-bridge LLC resonant converter can be operated with either variable frequency control or fixed frequency control. Each control method has its own advantages and disadvantages. The two control methods can be integrated to form a hybrid control, where the converter is operated with variable frequency control at lower input voltage and phase-shift control at high input voltage. This the converter efficiency can be optimized in a wide input voltage range. This thesis analyzes the operation principle of the full-bridge LLC resonant converter under the two control methods, and the voltage gain characteristics of the converter are analyzed by time domain analysis method. In order to further increase the efficiency, the thesis proposes a optimization solution for the switching point of the input voltage between the variable-frequency control and phase-shifted control, and the parameters design for the resonant tank by fundamental harmonic approximation method is presented. The realization and design of the control circuit is presented. The small-signal characteristics of the converter are obtained by simulation method, and the parameter design for control loop is provided.

Two 3 kW prototypes adopting hybrid control and variable frequency control, respectively, are fabricated and tested in the lab. The measured efficiencies under the two control methods show that the hybrid control can achieve a better efficiency over the entire wide input voltage range compared to the variable frequency control.

Keywords: LLC resonant converter; Variable frequency control; Pulse-width modulation; Hybrid

control; Small-signal characteristics.

II

南京航空航天大学硕士学位论文

目 录

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