【作者】 王涛；

【导师】 陈阿莲；

【作者基本信息】 山东大学 ， 电力电子与电力传动， 2020， 硕士

【摘要】 在能源互联网和新能源汽车等领域,需要通过DC-DC变换器实现能量的双向变换。双有源桥(Dual Active Bridge,DAB)变换器因具有功率密度高和允许能量双向传输的特点,适合作为新一代的电力接口设备,受到越来越多的关注。针对高电压和大功率场景,采用三电平结构的DAB变换器能有效满足耐压需求,降低系统成本并方便控制器设计,具有重要的开发意义。然而有关三电平DAB控制策略,尤其是对于提升传输效率、降低开关损耗和优化电流应力等方面的研究亟待完善。为解决上述问题,本文设计了相应的优化控制策略,主要工作如下。首先,对于三电平DAB的各类拓扑形式进行了分析总结,得出拓扑演变规律,目前全桥结构的DAB变换器应用电压等级最高,适用场合最广,且其调制策略可推广应用于其他三电平DAB。因此本文确定以全桥结构的三电平双有源桥式DC-DC隔离变换器为研究对象。然后,针对高频工作条件下开关损耗大和传输效率低的问题,本文从软开关和最低回流功率两项指标入手,基于双重移相调制策略,设计了三电平全桥式DAB变换器的软开关条件,使所有开关管工作在软开关状态;在保证软开关的同时,进一步设计了控制算法,实现DAB回流功率最低。另外,还通过分析DAB中的数学关系,提出了一种工作在移相调制方式下的优化控制策略,使DAB能根据目标功率与环境母线电压实时调节变量以达到最优运行工况。其次,基于三电平全桥式DAB的三重调制方式优化DAB谐波含量和提升电磁兼容性能。对该调制策略的工作原理进行了详细的说明,并在这种调制方式下进行了软开关和最低电流应力的双重优化设计。为了保证所有开关管的软开关特性,本文对所有可能的工作模态进行了划分,并建立了各模态的数学模型,计算得出了所有开关管软开通的实现条件。此外,为了优化电路中的电流应力,本文还对各模态工作下的电流应力进行了分析,并通过迭代算法在各模态内寻求最优的控制变量,使得DAB能以最小电流应力状态运行。最后,本文基于Simulink平台,对提出的控制策略进行了仿真验证,还搭建了一台三电平全桥式DAB原型机以供后续研究使用。更多还原

【Abstract】 In the Energy Internet and electric vehicle areas,DC-DC converters play a more and more important role.Dual active bridge(DAB)converter has the characteristics of high power density,bidirectional transmission capacity,and other advantages,which make it suitable for the new generation of power interface equipment.For high voltage and high power scenarios,the DAB with the three-level structure can effectively meet the voltage demand,reduce the system cost,and facilitate the controller design,which has great development significance.At present,the control strategy about the three-level DAB still needs to be improved,especially in the fields of improving transmission efficiency,reducing switching loss,and optimizing current stress.To solve these problems,an optimal control strategy is designed in this paper.The main arrangements of this dissertation are as follows.Firstly,all kinds of the topology of three-level DAB are summarized,and the principles of topology evolution are obtained.At present,the application voltage of the full-bridge DAB structure is the highest,and this type of DAB is most widely used.Besides,its modulation strategy can be extended and applied to other three-level DAB converters.As a result,the three-level dual-active bridge DC-DC isolated converter with a full-bridge structure is the main research target.To solve the switching loss and low-efficiency problems when DAB switching frequency is high,this paper designs a boundary condition that can ensure all the switches of three-level DAB to operate at soft-switching states.This paper also designs a control algorithm which can both ensure the soft-switching and minimum of the DAB backflow power.Besides,by analyzing the equation of DAB states variables,a phase-shift based optimized control strategy is proposed,which makes DAB can adjust two modulation variables in real-time according to the ratio of DAB input and output voltages.Then,to further optimize the DAB harmonic content and enhance the EMC performance by using the triple modulation mode,the working principle of this modulation strategy is explained in detail in this paper.On this basis,the theoretical implementation of its zero voltage switching state is also analyzed on the mathematical model and the working modes are divided,when the bilateral soft switching realization conditions are obtained.To optimize the current stress in the circuit under this modulation strategy and further depress the demand for the device’s current index,the optimization design for the current stress is also unified into the strategy optimization.According to the ratio of actual port voltages,the expected modulation variables are calculated and the soft switching realization is judged.Then a set of control variables with minimum transfer current stress are selected out.This paper mainly verifies the research target through Simulink,and a three-level DAB prototype is built as the research platform.更多还原