因為石油能源逐漸枯竭、環保意識抬頭及科技的進步下，近年來雙向直流-直流轉換器應用在能量儲存系統上-例如：電動車內的電池、大容值電容等越來越受到重視，而能量儲存系統根據不同的應用有許多的種類，基於電壓範圍可分為兩種：高壓能量儲存系統及低壓能量儲存系統，因此雙向直流-直流轉換器專注於這兩種系統的應用。雙向直流-直流轉換器主要分為兩種：隔離式雙向直流-直流轉換器及非隔離式雙向直流-直流轉換器，本論文提出新型控制法及新型架構的隔離式直流-直流轉換器及非隔離式直流-直流轉換器，此轉換器可應用於高壓及低壓能量儲存系統。
新型控制方案的隔離型雙向橋式直流-直流轉換器被提出以實現全功率範圍零電壓切換（ZVS）用於全混合 (full hybrid) 插電式 (plug-in) 或電動車輛等高電壓水平下的儲能系統 (ESS). 這種控制法由於減少了開關損耗所以顯著提升效率。此外，相比於傳統控制法需要根據功率範圍在每個操作模式下進行大量運算導致系統在動態負載下的不穩定性和不可靠性，新型控制法需要較少的計算和操作模式。在一些特定的應用中，儲能系統 (ESS) 需要非隔離的雙向直流-直流轉換器來提高功率密度和降低成本。所以採用了具有新穎控制方案的非隔離式雙向升/降壓轉換器，以控制佔空比和相移的方式實現全開關的零電壓切換 (ZVS) 並優化電感電流的漣波. 因此，與傳統拓撲相比有非常高的效率。
由於低壓的電源儲能系統通常被運用在電動車或汽車，因此提出將雙向直流/直流轉換器做低壓的應用。基於高功率密度以及穩定度的考量，選用架構為三相雙向電路。然而，如何達到零電壓切換仍然是個很大的問題，例如：一般的DAB架構，在輕載時無法達成零電壓切換。因此，本論文將會針對在三相雙向電路的零電壓切換條件進行探討，透過在高壓側加入一個諧振槽去保證在非常輕載的情況下也能達成零電壓切換。除此之外，利用相移控制以及頻率控制去達成在低壓電池端開關的零電壓切換，以及拓展在非常輕載的零電壓切換範圍。此外，將Y型接法運用在高壓側以減少一次側變壓器的電壓應力；將△型接法運用在低壓電池側去降低電流應力，使在變壓器上的干擾與損耗有明顯的下降。在中低壓的應用，提出具有高電壓增益、低開關電壓應力以及可擴大可能性的新非隔離式雙向電路。在論文中，會提到兩相雙向電路的分析與特性。順向與逆向的工作原理都跟降壓轉換器與升壓轉換器十分相近，因此電路可以根據電感的設計，操作在CCM、DCM或TCM。另外，控制器使用類似傳統式轉換器所運用的。結果顯示，在兩相電路比起一般的轉換器，每一個開關的電壓應力會下降兩倍。同時，為了證明論文架構的優點，將會探討一些衍生的電路。

The bidirectional DC-DC converters for the energy storage systems (ESSs) such as batteries or ultra-capacitors in the electric vehicle or automotive systems have been paid more attention in recent years due to the developing of the technology and the exhaustion of the fossil fuel energy and their environmental concerns. There are numerous types of the ESSs depended on the specific applications. However, the ESSs is basically categorized into two main groups based on the voltage level: high voltage ESSs and low voltage ESSs. Therefore, the bidirectional DC-DC converters have been focused on these two voltage level applications. There are two main particular types of the bidirectional converters: isolated and non-isolated bidirectional DC-DC converters. In this dissertation, the new control algorithm and the new topology of the non-isolated and isolated bidirectional DC-DC converter for the high and low voltage level of the ESSs are proposed.
At high voltage level of the ESSs such as full hybrid/ plug-in or electric vehicle, the isolated dual-active-bridge DC-DC converter is proposed with the novel control scheme to achieve the zero-voltage switching (ZVS) in the whole power range. With this controller, the efficiency is improved significantly due to the reduction of the switching losses. Moreover, the controller requires less calculation and operating modes since the conventional control scheme needs a lot of calculations in every operating mode depending on the power range, results in the instability and unreliability of the system in the dynamic load. In some specific applications, the ESSs require the non-isolated bidirectional DC-DC converter to improve the power density and cost. Therefore, the non-isolated bidirectional buck/boost converter with the novel control scheme is employed. The duty ratio and the phase shift are controllable to achieve the ZVS for all switches while optimizing the ripple of the inductor current. Therefore, the efficiency is extremely high compared to the conventional topology.
Since the low voltage ESSs were employed for the electric vehicle or automotive applications, the low voltage applications of the bidirectional DC-DC converter was proposed. The three-phase bidirectional converter has been employed because of its advantages such as high power density and stability. However, the ZVS achievement is still a big problem. Therefore, this dissertation focused on the ZVS condition for the three-phase converter. A resonant tank was applied at the high side to assure the ZVS even at very light load condition. Moreover, the combination of phase shift control algorithm and frequency modulation was proposed to achieve ZVS at low side battery and extend the ZVS range even at very light load condition. Furthermore, the wye connection was employed at the high side to reduce the voltage stress of the primary transformer and the delta connection was introduced at low side batteries to reduce the current stress. Then the noises and losses of the transformer are reduced significantly. In the low and medium application, the new bidirectional non-isolated converter with high voltage gain, low switches voltage stress, and expandable possibility is proposed. In this dissertation, the analysis and performance of the two-phase bidirectional converter are presented. The operating principle of the forward or reverse mode is similar to that of the conventional buck or boost converter. Therefore, the proposed converter can be operated in the continuous conduction mode, discontinuous conduction mode, depending on the design of the inductors. Moreover, the simple controller is similar to that used in the traditional converter. Results show that the voltage stress on every switch is reduced two times in the two-phase converter compared with the conventional converter. Additionally, the derivate converters are discussed to demonstrate the advantage of the proposed topology.

[1] M. Kebriaei, A. H. Niasar, B. Asaei, “Hybrid Electric Vehicles: An Overview”, International Conference on Connected Vehicles and Expo (ICCVE), Oct. 2015.
[2] D. D. C. Lu and V. G. Agelidis, “Photovoltaic-Battery-Powered DC Bus System for Common Portable Electronic Devices,” IEEE Trans. Power Electrons., vol. 24, no. 3, pp. 849-855, Mar. 2009.
[3] M. Yilmaz, P. T. Krein, “Review of Charging Power Levels and Infrastructure for Plug-In Electric and Hybrid Vehicles and Commentary on Unidirectional Charging,” 2012 IEE Intranational Electrical Vehicle Conference (IEVC 2012), Mar. 2012.
[4] R. M. Schupbach and J. C. Balda, “Comparing DC–DC Converters for Power Management in Hybrid Electric Vehicles,” in Proc. IEMDC, Jun. 2003, vol. 3, pp. 1369–1374.
[5] P. F. Ribeiro, B. K. Johnson, M. L. Crow, A. Arsoy, Y. Liu, “Energy Storage Systems for Advanced Power Applications,” Proceedings of the IEEE, vol. 89, no. 12, pp. 1744-1756, Dec. 2001.
[6] Y. Tsuruta and A. Kawamura, “QRAS and SAZZ Chopper for HEV Drive Application,” in Proc. PCC, Nagoya, Japan, Apr. 2007, pp. 1260–1267.
[7] M. Anun, M. Ordonez, I. Galiano and G. Oggier, “Bidirectional Power Flow with Constant Power Load in Electric Vehicles: A Non-linear Strategy for Buck+Boost Cascade Converters,” in Proc. IEEE Appl. Power Electron. Conf. Expo., 2014, pp. 1697–1703.
[8] K. Chong-Eun, H. Sang-Kyoo, Y. Kang-Hyun, L. Woo-Jin, and M. Gun-Woo, “A New High Efficiency ZVZCS Bi-Directional DC/DC Converter for 42V Power System of HEVs,” in Proc. IEEE PESC, Recife, Brazil, Sep. 2005, pp. 792–797.
[9] V. V. S. K Bhajana, S. R. Reddy, “A Novel ZVS-ZCS Bidirectional DC-DC Converter for Fuel Cell and Battery Application,” on IEEE PEDS 2009, pp. 12-17.
[10] F. Z. Peng, Li Hui, Su Gui-Jia, J. S. Lawler, “A New ZVS Bidirectional DC-DC Converter for Fuel Cell and Battery Application,” Trans. Power Electronics, vol. 19, pp. 54-65, 2004.
[11] F. Caricchi, F. Crescimbiri, and A. Di Napoli, “20 kW Water-Cooled Prototype of a Buck–Boost Bidirectional DC–DC Converter Topology for Electrical Vehicle Motor Drives,” in Proc. IEEE APEC, Mar. 1995, vol. 2, pp. 887–892
[12] D. H. Kim and B. K. Lee, “An Enhanced Control Algorithm for Improving the Light-Load Efficiency of Non-inverting Synchronous Buck-Boost Converters,” IEEE Trans. Power Electrons., vol. 31, no. 5, May 2016.
[13] Y.J. Lee, A. Khaligh, A. Chakraborty, A. Emadi, “Digital Combination of Buck and Boost Converters to Control a Positive Buck-Boost Converter and Improve the Output Transients,” Trans. Power Electronics, vol. 24, pp. 1267-1279, 2009.
[14] L. Solero, D. Boroyevich, Y. P. Li, and F. C. Lee, “Design of Resonant Circuit for Zero-Current-Transition Techniques in 100-kW PEBB Applications,” IEEE Trans. Ind. Appl., vol. 39, no. 6, pp. 1783–1794, Nov. 2003.
[15] C. M. Young, Y. S. Cheng, B. R. Peng, S. H. Chi and Z. Z. Yang, “Design and Implementation of a High-Efficiency Bidirectional DC-DC Converter,”Future Energy Electronics Conference (IFEEC) 2015 IEEE 2nd International, pp. 1-5, 2015.
[16] Y. E. Wu, K. C. Huang, M. X. Li, “A Bidirectional DC/DC Converter Charge/Discharge Controller for Solar Energy Illumination System Integrating Synchronous Rectification SEPIC Converter and Active Clamp Flyback Converter, ” International Journal of Circuit Theory and Applications, vol. 44, no.2, pp. 305-327, Apr. 2015.
[17] S. Waffler, J.W. Kolar, “A Novel Low-Loss Modulation Strategy for High-Power Bidirectional Buck+Boost Converters,” IEEE Trans. Power Electrons., vol. 24, no. 6, June 2009.
[18] Zhao Biao, Song Qiang, Liu Wenhua, and Sun Yangdong, ‘Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System’, IEEE Trans. Power Electron., pp. 4091 - 4106 Vol. 29, Issue: 8, Aug. 2014.
[19] Alonso, A. R., Sebastian, J., Lamar, D. G., Hernando, M. M., and Vazquez, A., ‘An overall study of a dual active bridge for bidirectional dc/dc conversion’, Proc. ECCE, pp.1129 -1135, 2010.
[20] Harrye Yasen, A. and Ahmed, K. H. ‘Reactive Power Minimization of Dual Active Bridge DC/DC Converter with Triple Phase Shift Control using Neural Network’, International Conference on Renewable Energy Research and Applications, pp. 566-571.
[21] Kuiyuan, W., De Silva, C. W., and Dunford, W. G., ‘Stability Analysis of Isolated Bidirectional Dual Active Full-Bridge DC-DC Converter with Triple Phase-Shift Control’, IEEE Trans. Power Electron., vol. 27, pp. 2007-2017, 2012.
[22] Shi, H. C., Wen, H. Q., Chen, J., Hu, Y. H., Jiang, L., Chen, G. P., ‘Minimum Reactive Power Scheme of Dual Active Bridge DC-DC Converter with Three-Level Modulated Phase-Shift Control’, IEEE. Trans. Industry Applications, vol. 53, pp. 5573-5586, 2017.
[23] Zhao Biao,Yu Qingguang and Sun Weixin, ‘Bi-directional Full-bridge DC-DC Converters with Dual-phase-shifting Control and Its Backflow Power Characteristic Analysis’, Proceedings of the CSEE, 2012. 32(012):43-50.
[24] Choi, W., Rho, K. M., and Cho, B. H., ‘Fundamental Duty Modulation of Dual-Active-Bridge Converter for Wide-Range Operation’, IEEE Trans. Power Electron., vol. 31, no. 6, pp. 4048-4064, 2016.
[25] Higa, H., Itoh, J. I., ‘Extension of Zero-Voltage Switching Range in Dual Active Bridge Converter by Switched Auxilary Inductance’, IEEE Energy Conversion Congress and Exposition, pp. 5324- 5331, 2017.
[26] Krismer, F. and Kolar, J. W. ‘Efficiency-optimized high current dual active bridge converter for automotive applications’, IEEE Trans. Ind. Electron., 2011.
[27] Ortiz, G., Biela, J., Bortis, D., and Kolar, J. W., ‘1 Megawatt, 20 kHz, isolated, bidirectional 12kV to 1.2kV dc-dc converter for renewable energy applications’, International Power Electronics Conference (IPEC), 2010, pp. 3212-3219, Jun. 2010.
[28] Hua Bai, C. Mi, "Eliminate Reactive Power and Increase System Efficiency of Isolated Bidirectional Dual-Active-Bridge DC-DC Converters Using Novel Dual-Phase-Shift Control," IEEE Trans. Power Electron., vol.23, no.6, pp.2905-2914, Nov. 2008.
[29] Zhiyu Shen, Burgos, R., Boroyevich, D., and Wang, F., ‘Soft-switching capability analysis of a dual active bridge dc-dc converter’, Electric Ship Technologies Symposium, 2009. ESTS 2009. IEEE, vol., no., pp.334-339, 20-22 April 2009.
[30] Zhou Haihua, A.M. Khambadkone, "Hybrid Modulation for Dual Active Bridge Bi-Directional Converter with Extended Power Range for Ultra-capacitor Application," Industry Applications Society Annual Meeting, 2008. IAS '08. IEEE, pp.1-8, 5-9 Oct. 2008.
[31] K. Tytelmaier, O. Husev, O. Veligorskyi, R. Yershov, "A review of non-isolated bidirectional DC-DC converters for energy storage systems", Int. Young Scientists Forum on Applied Physics and Engineering (YSF), pp. 22-28, 2016.
[32] M. A. Sofla, L. Wang, "Control of dc-dc bidirectional converters for interfacing batteries in microgrids", Proc. of IEEE Power Systems Conf. and Exposition, March 20–23, 2011.
[33] M. Godoy Simões, C.L. Lute, A.N. Alsaleem, D.I. Brandao, J. A. Pomilio, "Bidirectional floating interleaved buck-boost DC-DC converter applied to residential PV power systems", Proc. of IEEE Power Systems Conference, Mar. 10–13, 2015.
[34] J. Zhang, J.-S. Lai, R.-Y. Kim, W. Yu, "High-power density design of a soft-switching high-power bidirectional DC- DC converter", IEEE Transactions on Power Electronics, vol. 22, no. 4, pp. 1145-1153, July 2007.
[35] Il-Oun Lee, Shin-young Cho, Gun-Woo Moon, "Interleaved Buck Converter having low switching losses and improved step-down conversion ratio", IEEE 8th International Power Electronics-ECCE Asia, The Shilla Jeju, Korea, pp. 2136-2143, Jun. 2011.
[36] Ratil H. Ashique, Zainal Salam, Mohd Junaidi Abdul Aziz, "A high gain soft switching non-isolated bidirectional DC-DC converter", Power and Energy (PECon) 2016 IEEE International Conference on, pp. 417-422, 2016.
[37] J. Feng, Y. Hu, W. Chen, and C. C. Wen, “ZVS Analysis of Asymmetrical Half-Bridge Converter,” IEEE PESC, vol. 1 pp.147-234, 2001.
[38] M. Ahmadi, K. Shenai, “New, Efficient, Low-Stress Buck/Boost Bidirectional DC- DC Converter,” Energy Tech 2012 IEEE, pp. 1-6, 2012.
[39] F. C. Lee, “High-Frequency Quasi-Resonant and Multi-Resonant Converter Technologies,” IEEE IECON, pp. 509-521, 1988.
[40] P. Thumalla, Z. Zhang, M. A. E. Andersen, “High Voltage Bi-directional Flyback Converter for Capacitive Actuator,” 15th European Conference on Power Electronics and Applications (EPE), pp. 1-10, 2013.
[41] D. M. Divan, L. Malesani, P. Tenti, and V. Toigo, “A Synchronized Resonant DC Link Converter for Soft-Switched PWM,” IEEE Trans. Ind. Appl., vol. 29, no. 2, pp. 940–948, Sep. 1993.
[42] R. Gurunathan and A. K. S. Bhat, “Zero-Voltage Switching DC Link Single Phase Pulse Width-Modulated Voltage Source Inverter,” IEEE Trans. Power Electron., vol. 22, no. 5, pp. 1610–1618, Sep. 2007.
[43] R. W. De Doncker, D. M. Divian, M. H. Kheraluwala, “A Three Phase Soft- Switched High Power Density DC/DC Converter for High Power Applications,” in Conf. Rec. IEEE IAS Annu. Meeting, Pittsburgh, PA, Oct. 2-7, 1998, pp. 796-805.
[44] Y. Li and F. C. Lee, “A Comparative Study of a Family of Zero-Current Transition Schemes for Three-Phase Inverter Applications,” in Proc. IEEE APEC, Mar. 2001, vol. 2, pp. 1158–1164.
[45] D. D. Nguyen, D. T. Nguyen and G. Fujita, “Dual Active Bridge Series Resonant Converter: A New Control Strategy Using Phase-Shifting Combined Frequency Modulation,” IEEE Trans. Power Electron., pp.1215-1222, 2015.
[46] Z. Wang and H. Li, “Three-Phase Bidirectional DC-DC Converter with Enhanced Current Sharing Capability,” IEEE ECCE, pp.1116-1122, 2010.
[47] Z. Wang and H. Li, “A Soft Switching Three-Phase Current-Fed Bidirectional DC-DC Converter with High Efficiency Over a Wide Input Voltage Range,” IEEE Trans. Power Electron., pp.669-684, 2012.
[48] A. Mohammadpour, T. Li and L. Parsa, “Three-Phase Current-Fed Zero Current Switching Phase-Shift PWM DC-DC Converter,” IEEE Trans. Power Electron., 2014.
[49] Y. K. Lo, J. Y. Lin, C. Y. Lin, “Analysis and Design of a Half-Bridge LLC Series Resonant Converter Employing two Transformers,” International Journal of Circuit Theory and Applications, pp. 985-998, 2011.
[50] Y. K. Lo, J. Y. Lin, "Active-Clamping ZVS Flyback Converter Employing Two Transformers", IEEE Trans. on Power Electron., vol. 22, no. 6, pp. 2416-2423, Nov. 2007.
[51] H. M. O. Filho, D. S. Oliveira Jr. and P. P. Praca, “Steady-State Analysis of a ZVS Bidirectional Isolated Three-Phase DC-DC Converter Using Dual-Phase-Shift Control with Variable Duty Cycle,” IEEE Trans. Power Electron. , pp.1863-1872, 2016.
[52] D. V. Ghodke, K. Chatterjee, and B. G. Fernandes, “Three-Phase Three-Level, Soft Switched, Phase Shifted PWM DC-DC Converter for High Power Applications,” IEEE Trans. Power Electron., pp.1214-1227, 2008.
[53] H. Hoek, M. Neubert and R. W. De Doncker, “Enhanced Modulation Strategy for a Three-Phase Dual Active Bridge Boosting Efficiency of an Electric Vehicle Converter,” IEEE Trans. Power Electron., pp.5499-5507, 2013.
[54] H. M. O. Filho, D. S. Oliveira Jr. and C. E. Silva, “ZVS Bidirectional Isolated Three-Phase DC-DC Converter with Dual Phase-Shift and Variable Duty Cycle,”IEEE IAS, pp.1-8, 2012.
[55] J. Huang, Y. Wang, Z. Li, Y. Jiang and W. Lei, “Simultaneous PWM Control to Operate the Three-Phase Dual Active Bridge Converter Under Soft Switching in the Whole Load Range,” IEEE APEC, pp.2885-2891, 2015.
[56] R. Mirzahosseini and F. Tahami, “A Phase-Shift Three-Phase Bidirectional Series Resonant DC-DC Converter,” IECON, pp.1137-1143, 2011.
[57] M. Rakesh, P. S. Satya, A. Pramond, “Design and Implementation of Three-Phase Resonant DC-DC Converter for Low-Voltage High-Current Applications,” Journal of Electric Power Components and Systems, vol. 42, pp. 1249-1265, 2014.
[58] M. B. E. Kattel, R. Mayer, S. V. G. Oliveira, “A Three Phase Flyback Current-Fed Push-Pull Bidirectional DC-DC Converter for DC Microgrid Application,” IEEE International Conf. Industry Applications, Mar. 2016.