【作者】 杨瑞；

【导师】 丁洪发；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2014， 博士

【摘要】 高频化运行是电力电子变换器实现高功率密度和高集成度的重要途径。谐振变换器具有良好的软开关优势,可以借助自身电路环境实现器件的零电压开关或零电流开关,有利于降低变换器的损耗。而LCC谐振变换器兼顾了二元件谐振变换器各自的优点,具有抵抗负载开路和短路、兼容变压器寄生参数的能力,是一种常见的用来实现高压直流电源的电路结构。本文分析比较了当前建模方法应对变换器非线性特性的不足和精确建模所需要解决的关键性问题,提出了利用状态空间法迭代求解实现变换器不同电流模式下精确建模及开关特性分析的思路,为变换器的设计和控制提供了较精确的模型基础,主要工作如下：针对LCC谐振变换器在不同频率下的响应特点,分析给出了以逆变桥和整流桥导通方向为依据的谐振变换器拓扑等效的一般性步骤,推导在不同拓扑下系统的状态方程和状态变量的表达式,分析了逆变桥不同结构和谐振元件初始储能对状态变量响应轨迹的影响；分析了开关周期内能量传递的过程,并在稳态电压恒定的基础上提出了谐振回路与负载侧能量平衡的数学描述。针对较低开关频率下的零电流开关运行,研究了LCC谐振变换器在断续电流模式下的工作过程及数学描述：提出了根据输出电压范围判断变换器等效拓扑交替序列的依据。在等效拓扑的状态空间方程基础上,利用迭代法推导了谐振电流、谐振电压及负载侧整流电流与输出电压间的解析表达式。根据该表达式分别推导了谐振电流正负半波持续时间及总响应时长,并提出了满足零电流开关的最优驱动脉宽概念及相应的配置原则；建立了负载与开关频率对输出电压的共同作用关系,分析了串并联电容比对输出电压增益的影响。通过数字仿真和实验的方式验证了解析模型的正确性。针对较高开关频率下的零电压开关运行,研究了LCC谐振变换器在连续电流模式下的工作过程及数学描述：通过驱动信号闭锁时刻与负载整流器导通时刻的相互关系,确定了变换器等效拓扑的交替序列,推导了不同序列下谐振电流和谐振电压的相互作用关系；针对稳定感性运行两种特解情况,求得了开关频率、负载、输出电压增益三者的映射关系,将特解推广到一般情况分别得到了不同交替顺序下变换器的约束方程,给出了以虚拟角度定义域分析为基础的方程求解过程；分析指出了变换器出现连续电流容性运行的原因及条件,提出了严格意义上满足变换器连续电流感性运行的开关频率和负载变化范围；总结归纳了连续电流模式变换器稳态求解的一般性过程,得到了变换器在连续电流模式不同序列下的精确电压增益曲线,分析了开关频率和负载品质因数对增益的影响趋势,验证了所得数学模型具有较高精确度的特点；提出了满足开关器件零电压开关的驱动信号占空比范围,分析了开关频率和负载电阻变化对功率因数的影响。更多还原

【Abstract】 High frequency operation is an important method to achieve high power density and high integration in power electronic converters. Resonant converter possesses a good soft switching characteristic of utilizing inductor and capacitor to realize zero voltage switching or zero current switching. The LCC type series parallel resonant converter is a widely used high voltage DC power supply for acquiring the respective advantages of two elements resonant converter, be compatible with parasitic capacitance of high frequency step up transformer, and the ability to resist open load or short load.This dissertation study the analysis and model of LCC resonant converter in different current response condition, especially concentrate on the non-linearity resulting from the parallel capacitor behavior in one switching period. An analytical model based on the successive state space solving has been proposed, for obtaining mathematic relation among the various parameters of converter.The research will start with the general topology equivalent procedure. The state equations involved each variable in resonant tank have been deduced. Since the inverter can be realized by different structures, the response trajectory has been discussed within or without initial energy storage. In order to establish the interaction relationship between the load and the resonant tank, the energy transfer process is analyzed, and then a detailed expression of energy balance is given.Considering the series parallel characteristic in high power resonant charging application, the converter operated in discontinuous current mode (DCM) is analyzed. For a better understanding of voltage gain and soft switching environment, a sequence distinguishing method of equivalent topologies alternating has been proposed according to the different ranges of output voltage. Because the load impact on resonant tank is not direct, we can conveniently work out the analytical expressions of inductor current, capacitor voltage, and the rectifier current. By the response time of current in each sequence, an optimal driving signal width satisfying zero current switching is proposed. Accurate voltage gain with switching frequency and load has been given. An excellent agreement is obtained when comparing numerical values calculated by the proposed model to the simulation and to the experimental results.To achieve a high precision model of converter operated in continuous current mode (CCM), a pure analytical solving process is presented. Since the CCM response is more complicated than DCM, the sequence of equivalent topologies alternating is firstly distinguished by relation between turn off time and rectifier turn on time. Moreover, the analytical expressions of inductor current, capacitor voltage, and the rectifier current are deduced. The mapping relation about switching frequency, load, and output voltage in two particular situations is analyzed. Analytic constraint equations in general condition is proposed by the extending of particular situations. The study explains why the converter will show capacitive waves under lower switching frequency. The strict range of output voltage and load that makes converter in inductive operation is proposed. The steady state solving procedure of converter in CCM is generalized. The dissertation analyses the load and switching frequency influence on voltage gain, and acquires an analytical model of the three variables. The power factor performance is also discussed.更多还原