返回
类型 综合研究 预答辩日期 2018-01-10
开始(开题)日期 2014-10-14 论文结束日期 2017-10-16
地点 逸夫科技馆北四楼403室 论文选题来源 国家自然科学基金项目     论文字数 7.5 (万字)
题目 双向全桥直流变换器的分析模型与关键技术的研究
主题词 简化零电压开关算法,调制算法,直流偏置补偿,模型
摘要 随着新能源产业的快速发展,电池储能系统成为新能源电力系统的重要组成部分,双向直流变换器是该系统的核心,其性能优劣直接影响了新能源电力系统的变换效率与系统可靠。由于储能电池在充放电过程中因内阻变化而产生较大的输出电压变化,同时电池本身因充电或放电同样产生输出电压的变化,从而使得目前的双向直流变换器无法实现宽电压变化范围内的高效率和高可靠变换。 目前大多数双向变换器由单向变换器演变而来,结构上不对称,反向变换特性远逊于正向变换特性,整体性能不佳。双向全桥直流变换器则属于双向直流变换器中结构较为简洁的一种变换器,该变换器在结构上完全对称,功率传输方向可以实现无缝切换。相比于其它双向变换器等结构,其正向工作和反向工作都有非常好的升降压能力,成本低,可以实现高效的能量传输。但是这种变换器在电压传输比偏离变压器匝比时输入输出环流增大、软开关丢失,从而电流应力变高,整体性能恶化。除此之外,该变换器还存在重载环路响应慢、调制算法复杂、存在直流偏置等问题。 针对双向全桥变换器所存在的上述问题,本文着重研究双向全桥变换器在宽电压变化范围内的特性,通过研究其变换效率模型和小信号模型、开关算法及直流偏置补偿方法等,从而提高变换整体效率等性能指标。论文主要研究内容和创新点总结如下: (1)提出了双向全桥直流变换器的效率模型。传统的双向全桥变换器效率计算依赖于仿真软件,通过使用P-spice中厂商提供的器件模型和变压器模型可以对双向全桥变换器的效率进行计算分析。但是P-spice单次仿真时间过长且容易出现不收敛的情况,并且在重载时无法考虑温度的反向影响,对于调制算法的优化与系统的设计极为不利。所提出的效率模型采用等效寄生电阻的概念计算变换器关键电流/电压波形,在计算出电流/电压波形基础上,进一步通过微积分方法计算磁芯损耗和开关损耗,并且考虑了温度环对于损耗的反向作用。该模型在保证计算精度在20%到100%负载下达到96%以上的同时其计算时间减小为P-spice计算时间的1/100。通过该效率模型可以在设计初期指导关键器件的选型,算法的选择与优化,从而缩短开发周期。 (2)提出了基于一种行为类比方式的双向全桥变换器功率级等效小信号模型。传统的双向全桥变换器的小信号模型在建立状态方程后通过采用谐波分解的方式来获得,其计算结果依赖于所保留的谐波次数。这样的方式在计算精度和复杂度上难以折中,并且建模过程复杂。所提出的模型采用行为类比的方式建立了在行为上与双向全桥直流变换器功率级一致的等效数学模型,该数学模型完整地描述了双向全桥直流变换器的动态特性。基于此等效数学模型,本文进一步得出了双向全桥变换器小信号模型。与实测对比,该小信号模型在1/2开关频率以下误差在3%以内。该小信号模型适用于所有双向全桥变换器的调制算法,为双向全桥直流变换器的环路设计与控制算法选择提供了理论支持。 (3)基于零电压开关模型优化了调制算法。传统的调制算法中,基波占空比调制算法展现出最为优异的综合性能。该算法ZVS区域宽、电流环流小、功率传输范围大。但是由于该算法的推导采用了基波近似的方法,其导出结果包含多次反三角函数计算。复杂的反三角函数计算导致该算法计算周期过长而必须使用查表计算,而查表计算消耗大量内存使得成本无法降低。所提出的优化零电压开关算法在保证效率特性与基波占空比算法基本持平的同时,将单次计算的计算量从394个时钟周期减小到了47个时钟周期,降低了对于控制芯片资源的使用。 (4)提出了基于占空比数学模型的直流偏置补偿的方法。以往的研究仅给出了采用环路控制消除直流偏置的概念。本文进一步通过对双向全桥变换器直流偏置产生的机理进行分析建模,得出了双向全桥直流变换器功率级中占空比对于直流偏置影响的数学模型,基于该模型提出了直流电流偏置补偿的方法。实测结果表明采用该直流偏置补偿后的系统提升了1~2%的整体效率。 (5)提出了一种最小磁芯选择和励磁线选型的变压器磁集成设计方法。本文首先对两种不同绕制方式的变压器漏感进行了数学建模,通过该数学模型与变压器励磁电感的数学模型结合,得出了双向全桥直流变换器中最小磁芯选择的数学方法。其次将Dowell给出的涡流损耗计算公式进行修正并且应用于李兹线的损耗计算中,给出了双向全桥直流变换器中变压器李兹线的选型方法。最终得出了双向全桥直流变换器中变压器磁集成的整体设计方法,使得双向全桥变换器磁集成的正向设计得以实现。
英文题目 Study on the analysis model and key technology of the bidirectional full bridge DC-DC converter
英文主题词 Zero voltage switching, Simplified zero voltage switching modulation algorithm, Circulating current, Modulation method, DC bias compensation, Model
英文摘要 Due to the development of new energy, the battery energy storage system (BESS) has been an indispensible part of the power electronics system. In the BESS, the bidirectional DC-DC converter is the most important part. Its performance will affect the efficiency and robustness of the new energy power electronics system. Because of the existence of the battery’s parasite resistance and the variation of the battery’s intrinsic voltage in different state of charge (SOC), the DC-DC converter must be efficient and realiable when transferring enery in the wide voltage variation range condition. Nowdays, most of the bidirectional DC-DC converters are transformed from the unidirectional DC-DC converter, and the performance of the backward operation is much worse than the forward operation due to their asymmetry in structure. However, the bidirectional full bridge converter has a very simple and symmetrical structure, and the switching of the power flow direction is very smooth. These characteristics makes it excellent in disposing the buck and boost bidirectional operation with high efficieny and low cost. Although there are many advantages, the bidirectional full bridge DC-DC converters will suffer big circulating current and loss of zero voltage switching (ZVS) which make a high current stress, and finally deteriorate the over performance when the voltage transfer ratio deviates from the transformer’s turn ratio. Besides, the problems like slow dynamic response, complex modulation algorithms and existence of DC bias current also makes this converter hard to be implemented in real application. For the purpose of solving these problems, this thsis focuses on the study of the characteristics of the bidirectional full bridge DC-DC converter in the wide voltage variation range condition. By studying the converter’s efficiency model, small signal model, modulation algorithm and DC bias compensation method, the performance like overall efficiency and so on are improved. The main research contents and inovations of this thsis are concluded as: (1) An overall efficiency model is proposed. Traditional efficiency calculation strongly relies on the simulation softwares. By using the P-spice model of the semiconductor device and magnetics provided by the suppliers, the efficiency of the bidirectional full bridge DC-DC converter can be estimated previously. However, there are always convergence problems during the simulation, and the simulation is time consuming. Besides, the backward effect of the temperature rise is too complicated to be implemented in the simulation. So when using the simulation method, the modulation method optimization and system design will be very inconvenient. The proposed model uses the concepts of equivalent parasote resistance to calculate the key waveforms of the bidirectional full bridge DC-DC converter. Based on these calculated waveforms, the core losses and switching losses are calculated out with consideration of the backward effect of the temperature rise. This model reduces the calculation time to 1/100 times of calculation time in P-spice simulation. By using this model, the selection of switch device, the selection and optimization of the modulation algorithm can be accomplished conveniently, and finally the development time can be reduced. (2) A small signal model based on the behavior analogy is proposed. Conventional small signal model of the bidirectional full bridge DC-DC converter is derived by using the harmonic analysis method and the state space method; The accuracy relies on how many harmonics are used. This method is hard to get a trade off between the accuracy and the complexity, and the modeling process is complicated. The proposed model is an equivalent mathematic model that derived based on the behavaior analogy of the bidirectional full bridge DC-DC converter. This model can describe the steady state and dynamic behaviors perfectly. Based on this equivalent mathematic model, the small signal model in frequency domain is derived. When compared to the test result, the error of this small signal model is less than 3% below half of the switching frequency. The proposed model can be used in any modulation method, and it can guide the design of the control loop and the selection of modulation method. (3) A modulation method is optimized based on the ZVS model. The fundamental duty modulation is proved to be the best one in the existing modulation methods. It shows a wide ZVS region, small circulating current and wide power transfer range. However, this modulation is derived based on the fundamental harmonic method. So the algorithm has many inverse trigonometric functions which will comsume a long time to calculate. The best way to reduce the calculation time is to use look-up table. But the look-up table will consume many memory resources. All in all, the cost is hard to be reduced. The proposed modulation method reduces the complexity of the algorithm while the performance is almost the same with the fundamental duty modulation. The calculation time is reduced from 347 clock cycles to 47 clock cycles. (4) A DC bias compensation method based on the duty cycle mathematic model is proposed. The previous researchs only give the concept of eliminating the DC bias by using control loop. Through further analyzing and modelling the mechanism of the DC bias’ formation, this thsis derives the mathematic model of the interrelationship between the duty cycle and the DC current bias. Then, a DC bias compensation method based on this model is proposed. The test result shows that it can improve the overall efficiency for about 1%~2%. (5) A magnetic integration method which can guide the selections of smallest magnetic core and Litz wire is proposed. The leakage inductance mathematic models of two typical transformer structures are given. Based on the combination of the leakage inductance model and the magnetizing inductance model, the size of the smallest magnetic core of the transformer can be derived. Besides, the eddy current loss model derived by Dowell is modified to be used in the Litz wire condition, and then the selection method of the Litz wire can be drived. These two contributions figure out the overall magnetic integration design method, and make the top down design of the magnetic integration in bidirectional full bridge DC-DC converter come ture.
学术讨论
主办单位时间地点报告人报告主题
苏州三星 2013年4月15日 苏州三星电子1号会议室 姚云鹏 多相Buck变换器环路小信号建模
东南大学ASIC工程中心 2013年8月13日 逸夫科技馆北三楼会议室 姚云鹏 高频变压器设计
东南大学ASIC工程中心 2014年11月3日 逸夫科技馆北三楼会议室 姚云鹏 功率MOSFET热设计
东南大学ASIC中心 2016年10月23日 逸夫科技馆401 白春风 Design of High Linearity PGAs
东南大学 2017年6月3日 东南大学四牌楼校区大礼堂 丁肇中 国际空间站上AMS实验的最新成果
东南大学ASIC工程中心 2012年6月10日 逸夫科技馆北三楼会议室 姚云鹏 快速响应Buck变换器环路设计方法
2017电力电子与变频电源新技术学术年会 2017年6月30日至7月2日 深圳汇川技术股份有限公司 赵争鸣 功率半导体开关器件多时间尺度瞬态建模
东南大学 2017年10月11日 九龙湖校区李文正图书馆润良报告厅 童文 5G和B5G关键技术挑战
     
学术会议
会议名称时间地点本人报告本人报告题目
South Asia Institute of Science and Engineering 2015年9月10日至12日 Kitakyushu, Japan Closed-Form Second-order Power Transmission Characteristic Model of the Isolated Dual Active Bridge Converter
Institute of Doctors Engineers and Scientists 2015年8月1日至2日 Bangalore,India Current Mode Buck Converter Using Sample and Hold Current Feedback Loop
     
代表作
论文名称
Zero-steady-state-error compensation method in application of peak current mode buck converter with
A Novel Compensator for Eliminating DC Magnetizing Current Bias in Hybrid Modulated Dual Active Brid
Hybrid modulation scheme for dual active bridge converter that employs the triangular modulation and
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
郭宇锋 正高 教授 博导 南京邮电大学
蔡跃明 正高 教授 博导 解放军理工大学
吴建辉 正高 教授 博导 东南大学
孙伟锋 正高 教授 博导 东南大学
秦明 正高 教授 博导 东南大学
李红 其他 其他 东南大学 秘书
      
答辩秘书信息
姓名职称工作单位备注
李红 其他 讲师 东南大学