LLC谐振变换器具有结构简单、效率高、高频化、体积小、功率密度高、便于磁集成等优点，但由于传统LLC谐振变换器增益范围窄，开关频率变化范围宽等问题，本文对全桥LLC谐振变换器的混合控制策略进行研究，具有理论意义和工程应用价值。

全桥LLC谐振变换器常见的控制方式有变频控制和移相控制，本文通过对全桥LLC谐振变换器变频与移相控制下的工作特性进行深入分析，结合变频与移相控制的特点，得出归一化增益大于1时采用变频控制，而小于1时采用移相控制的混合控制策略，可在变换器开关频率变化范围不大且保持副边整流管全负载范围内实现ZCS的情况下，拓宽LLC变换器的增益范围。同时本文依据对变频控制下的LLC谐振变换器进行详细分析，提出了改进基波近似等效法来分析变频控制下的LLC谐振变换器增益特性，通过对整流滤波网络进行重新建模，使得改进基波近似等效法相较传统基波近似等效法与实际变换器增益特性更为接近，有利于变换器的设计。依据变换器开关频率为二元谐振频率处归一化增益不受负载情况影响恒等于1的特性，选择开关频率工作在二元谐振点为两种控制方式的切换点，并通过对开关频率与二元谐振频率、输出电压与基准电压的比较得出两种控制方式的切换控制方法。

根据所提出的基于改进基波分析法的设计方法，最终研制了一台输出48V/15A的原理样机，实验表明混合控制策略可以很好的拓宽LLC谐振变换器的增益范围，实现副边整流管的全范围ZCS，验证了理论分析的正确性及设计方法的可行性。

LLC resonant converter has the advantages of simple structure, high efficiency, high frequency, small size, high power density, easy magnetic integration, etc., but due to the narrow gain range of traditional LLC resonant converter and wide switching frequency variation range, this paper studies the hybrid control strategy of full-bridge LLC resonant converter, which has theoretical significance and engineering application value.

Through an in-depth analysis of the working characteristics of the full-bridge LLC resonant converter under frequency conversion and phase shift control, combined with the characteristics of frequency conversion and phase shift control, it is concluded that the normalized gain is greater than 1, and the hybrid control strategy of phase shift control is used when the normalized gain is greater than 1, which can broaden the gain range of the LLC converter under the condition that the switching frequency change range of the converter is not large and ZCS is realized within the full load range of the secondary side rectifier. At the same time, based on the detailed analysis of the LLC resonant converter under frequency conversion control, this paper proposes an improved fundamental approximate equivalent method to analyze the gain characteristics of LLC resonant converter under frequency conversion control, and remodels the rectified filter network, so that the improved fundamental approximate equivalent method is closer to the gain characteristics of the actual converter than the traditional fundamental approximate equivalent method, which is conducive to the design of the converter. According to the characteristics that the normalized gain at the switching frequency of the converter is a binary resonant frequency that is not affected by the load condition and is always equal to 1, the switching frequency is selected to operate at the binary resonance point as the switching point of the two control modes, and the switching control method of the two control modes is obtained by comparing the switching frequency and the binary resonant frequency, output voltage and reference voltage.

According to the proposed design method based on the improved fundamental analysis method, a principle prototype with output 48V/15A was finally developped, and the experimental results show that the hybrid control strategy can well broaden the gain range of LLC resonant converter and realize the full range ZCS of the secondary rectifier, which verifies the correctness of the theoretical analysis and the feasibility of the design method.

[1] 李蕊,程诗尧,罗义钊,刘永强,柳玉銮.适用于可再生能源系统的新型高升压DC/DC变换器[J].电子器件,2022,45(05):1174-1181.

[2] 胡开元,华科,王智超,邵京伟.多端口分布式新能源输入低频电流纹波抑制[J].电力电子技术,2023,57(02):101-104.

[3] Yang B. Topology investigation for front end dc/dc power conversion for distributed power system. [D], Blacksburg, Virgina Polytechnic Institute and State University, 2003.

[4] 阮新波,严仰光.直流开关电源的软开关技术[M]. 北京: 科学出版社,2000.

[5] Severns R P. Topologies for three-element resonant converters [J]. IEEE Transactions on Power Electronics. 1992, 7(1): 89–98.

[6] Batarseh I. Resonant converter topologies with three and four energy storge elements [J]. IEEE Transactions on Power Electronics. 1994, 9(1): 64–73

[7] Steigerwald R L. A comparison of half-bridge resonant converter topologies [J]. IEEE Transactions on Power Electronics. 1988, 3(2): 174–182.

[8] 刘文霞,何向刚,吴方权,蒋泽甫,钟以林.新能源发电出力特性指标及其数据化应用[J].电网与清洁能源,2020,36(09):85-92.

[9] Pei Jinxin,Yao Jun,Liu Ruikuo,Zeng Deyin,Sun Peng,Zhang Hailin,Liu Yuan. Characteristic Analysis and Risk Assessment for Voltage–Frequency Coupled Transient Instability of Large-Scale Grid-Connected Renewable Energy Plants During LVRT [J]. IEEE Transactions on Industrial Electronics,2020,67(7).

[10] 郑重,耿华,杨耕.新能源发电系统并网逆变器的高电压穿越控制策略[J].中国电机工程学报,2015,35(06):1463-1472..

[11] 谢楠,陈卫民.基于分布式新能源发电的并网逆变器设计[J].水电能源科学,2012,30(02):203-206.

[12] Ye Guisen,Gao Feng,Fang Jingyang. A mission-driven two-step virtual machine commitment for energy saving of modern data centers through UPS and server coordinated optimizations[J]. Applied Energy,2022,322

[13] 熊宣. 基于服务器电源的新型宽输入LLC变换器研究[D].安徽工业大学,2021.

[14] 陈申,吕征宇,姚玮.LLC谐振型软开关直流变压器的研究与实现[J].电工技术学报,2012,27(10):163-169.

[15] Shen Yanfeng,Wang Huai,Al Durra Ahmed,Qin Zian,Blaabjerg Frede. A Structure-Reconfigurable Series Resonant DC–DC Converter With Wide-Input and Configurable-Output Voltages[J]. IEEE Transactions on Industry Applications,2019,55(2).

[16] X. Sun, X. Li, Y. Shen, B. Wang, and X. Guo, Dual-Bridge LLC Resonant Converter With Fixed Frequency PWM Control for Wide Input Applications[J]. IEEE Trans. Power Electronics, 2017, 32(1): 69–80.

[17] X. Sun, Y. Shen, Y. Zhu, and X. Guo, Interleaved Boost-Integrated LLC Resonant Converter With Fixed-Frequency PWM Control for Renewable Energy Generation Applications[J]. IEEE Trans. Power Electronics, 2015, 30(8): 4312–4326.

[18] Y. Gu, Z. Lu, L. Hang, Z. Qian, and G. Huang, Three-level LLC series resonant DC/DC converter[J]. IEEE Transactions on Power Electronics, 2005, 20(4): 781-789.

[19] W. Inam, K. K. Afridi, and D. J. Perreault, Variable Frequency Multiplier Technique for High Efficiency Conversion Over a Wide Operating Range[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2016, 4(2): 335–343.

[20] H. Hu, X. Fang, F. Chen, Z. J. Shen, and I. Batarseh, A Modified High-Efficiency LLC Converter With Two Transformers for Wide Input-Voltage Range Applications[J]. IEEE Trans. Power Electronics, 2013, 28(4): 1946–1960.

[21] W. Sun, Y. Xing, H. Wu, and J. Ding. Modified High-Efficiency LLC Converters With Two Split Resonant Branches for Wide Input-Voltage Range Applications[J]. IEEE Trans. on Power Electronics, 2018,33(9):7867-7879.

[22] 冯兴田,王世豪,周广睿,马文忠.基于移相控制的三相交错并联LLC谐振变换器均流控制策略[J].电力自动化设备,2021,41(12):166-171

[23] 刘松林,潘健,陈庆东,陈凤娇.宽输出LLC谐振变换器的定频PWM控制策略[J].电源学报,2023,21(01):26-34.

[24] 潘健,刘松林,石迪,宋豪杰,熊嘉鑫.宽电压应用定频LLC谐振变换器的PWM控制策略[J].电力科学与技术学报,2022,37(05):80-87

[25] 潘健,石迪,刘松林,熊嘉鑫,宋豪杰.具有混合控制策略的宽输出双全桥LLC谐振变换器[J].电源学报:1-16

[26] 邓钦瑞,何英杰,雷超,刘进军.CLLLC谐振变换器变频移相混合控制方法[J].电力自动化设备,2022,42(02):148-154

[27] 张朝阳. 基于多变量的全桥LLC谐振变换器混合控制策略研究[D].哈尔滨工业大学,2020

[28] 王念念. 宽范围LLC谐振变换器的控制策略与动态特性研究[D].北京交通大学,2021.

[29] 朱鑫彤. 宽范围谐振变换器复合调制与控制技术研究[D].电子科技大学,2022

[30] 陈一鸣. 宽范围软开关LCC谐振变换器电路及控制策略研究[D].西南交通大学,2018.

[31] 辛晓敏,荆龙,赵宇明,吴学智,牛靖凯,王鑫.变频控制LLC变换器的新型参数设计方法[J].电工电能新技术,2020,39(10):29-38.

[32] Erickson R W, Maksimovic D. Fundamentals of power electronics. 2nd Edition [M], Publisher: Kluwer Academic Publishers, 2001.

[33] Bhat A K S. Analysis and design of a fixed frequency LCL-type series resonant converter [J]. Proc. IEEE Applied Power Electronics Conference and Exposition (APEC), 1992: 253–260

[34] Raju G S N, Doradla S R. A novel LCL resonant converter with PWM control-analysis, simulation, and implementation [J]. Proc. IEEE Applied Power Electronics Conference and Exposition (APEC), 1994: 998–1004.，

[35] Bhat A K S. A fixed-frequency modified series-resonant converter: Analysis, design, and experimental results [J]. IEEE Transactions on Power Electronics, 1995, 10(6): 766–775.

[36] Lazar J F, Martinelli R. Steady-state analysis of the LLC series resonant converter [J]. Proc. IEEE Applied Power Electronics Conference and Exposition (APEC), 2001: 728–735.

[37] 冯大河. 利用Maple绘制波形图[J]. 中国科技信息. 2008, (17): 102

[38] 杜帅林. SiC MOSFET LLC 谐振变换器移相控制特性分析[D].浙江大学,2016

[39] 黄伟鹏. 宽范围输入LLC谐振变换器[D].北方工业大学,2021.

[40] 王柏樟,张卫平,张晓强.LLC谐振变换器设计中的权衡[J].电源学报,2019,17(06):50-56.

[41] Lee I O,Moon G W.The k-Q Analysis for An LLC Series Resonant Converter[J].IEEE transactions on power electronics,2014 29(1):13-16.