This dissertation proposes three new high-voltage-gain and high input voltage DC-to-DC converters for integration of renewable energy sources in 400 V DC distribution systems. The firstly topology named novel high-voltage-gain boost converter based on a coupled-inductors circuit featuring the proposed topology has the potential to lower the conduction loss due to smaller rms current and lower conduction resistance on switching devices. Therefore, the boost converter with coupled-inductor topology can be improved high gain even higher efficiency. Even at this high step-up ratio. The secondly high voltage-gain converter is based on an active-clamped forward/ flyback DC-to-DC converter with a voltage doubler. The proposed converter isolated DC-to-DC converter with a primary parallel and secondary series configuration for high-current input and high-voltage output applications to achieve high-step-up voltage-gains and low device stresses. The active-clamped technique is used to reduce the voltage spike and achieved the zero-voltage-switching (ZVS) turn-on of all power switches and zero-current-switching (ZCS) turn off mechanism for output rectifier diode. Low voltage-rating MOSFETs with low Rds(on) can be used to improve the high efficiency. Number thirdly, the multi-level SRC converter for high-input voltage applications is presented, four power switches are series connected in the proposed converter to reduced voltage stresses of the primary power switches. In addition to having ZVS turn on technique on the primary power-switches and ZCS turned off technique on the output-rectifier diodes to reduce the voltage stress on each switch without any clamp circuit. Moreover, it can effectively reduce the input-current-ripple resulting in reducing di/dt noise. Hence, the total power density performance can be further improved by using smaller electromagnetic interference (EMI) filter component.
This fascinating feature makes this topology suitable for renewable energy-related applications, such as PV grid or fuel-cell conditioning converters. In addition to operating principle theoretical analysis and design consideration, three hardware circuits, a novel high voltage-gain boost converter with coupled-inductors and the high voltage gain converter is based on an active-clamped forward/flyback DC-to-DC converter with a voltage doubler and multi-level SRC converter as the example described in Chapter 2, Chapter 3 and Chapter 4 respectively.

[1] A. M. S. S. Andrade, L. Schuch and M. L. da Silva Martins, "High step-up PV module integrated converter for PV energyh in FREEDM systems," in IEEE Transactions on Industry Applications, vol. 53, no. 2, pp. 1138-1148, March-April 2017
[2] C. L. Shen and P. C. Chiu, "Buck-boost-flyback integrated converter with single switch to achieve high voltage gain for PV or fuel-cell applications," in IET Power Electronics, vol. 9, no. 6, pp. 1228-1237, 5 18 2016.
[3] N. Subramanian, P. Prasanth, R. Srinivasan, R. R. Subesh and R. Seyezhai, "A comparative study of conventional, coupled inductor and RCN based interleaved boost converter for photo-voltaic applications," IET Chennai Fourth International Conference on Sustainable Energy and Intelligent Systems (SEISCON 2013), Chennai, 2013,
[4] Rong-Jong Wai and Rou-Yong Duan, "High step-up converter with coupled-inductor," in IEEE Transactions on Power Electronics, vol. 20, no. 5, pp. 1025-1035, Sept. 2005.
[5] F. L. Luo and H. Ye, "Positive output cascade boost converters," in IEE Proceedings - Electric Power Applications, vol. 151, no. 5, pp. 590-606, 9 Sept. 2004.
[6] C. Yan, P. J. Tseng, Y. K. Lo and H. J. Chiu, "Circuit component parameters design for dual-switch flyback converter," 2014 International Conference on Intelligent Green Building and Smart Grid (IGBSG), Taipei, 2014.
[7] N. Vázquez, F. Medina, C. Hernández, J. Arau and E. Vázquez, "Double tapped-inductor boost converter," in IET Power Electronics, vol. 8, no. 5, pp. 831-840, 5 2015.
[8] H. Moradi Sizkoohi, J. Milimonfared, M. Taheri and S. Salehi, "High step-up soft-switched dual-boost coupled-inductor-based converter integrating multipurpose coupled inductors with capacitor-diode stages," in IET Power Electronics, vol. 8, no. 9, pp. 1786-1797, 9 2015.
[9] K. C. Tseng, C. C. Huang and W. Y. Shih, "A high step-up converter with a voltage multiplier module for a photovoltaic system," in IEEE Transactions on Power Electronics, vol. 28, no. 6, pp. 3047-3057, June 2013.
[10] V. Balasubramanian, V. S. Nayagam and J. Pradeep, "Alleviate the voltage gain of high step-up dc to dc converter using quasi active switched inductor structure for renewable energy," 2017 International Conference on Computation of Power, Energy Information and Commuincation (ICCPEIC), Melmaruvathur, 2017, pp. 835-841.
[11] H. Moradi Sizkoohi, J. Milimonfared, M. Taheri and S. Salehi, "High step-up soft-switched dual-boost coupled-inductor-based converter integrating multipurpose coupled inductors with capacitor-diode stages," in IET Power Electronics, vol. 8, no. 9, pp. 1786-1797, 9 2015.
[12] L. Xue and J. Zhang, "Highly efficient secondary-resonant active clamp flyback converter," in IEEE Transactions on Industrial Electronics, vol. 65, no. 2, pp. 1235-1243, Feb. 2018.
[13] I. Zeltser, "Analysis of a low power, high voltage and high gain capacitor charger with output sourcing behavior," 2017 IEEE Applied Power Electronics Conference and Exposition (APEC), Tampa, FL, 2017.
[14] A. B. Shitole, S. Sathyan, H. M. Suryawanshi, G. G. Talapur and P. Chaturvedi, "Soft-switched high voltage gain boost-integrated flyback converter interfaced single-phase grid-tied inverter for SPV integration," in IEEE Transactions on Industry Applications, vol. 54, no. 1, pp. 482-493, Jan.-Feb. 2018.
[15] N. T. Quang, H. J. Chiu, Y. K. Lo and M. M. Alam, "Zero-voltage switching current-fed flyback converter for power factor correction application," in IET Power Electronics, vol. 6, no. 9, pp. 1971-1978, November 2013.
[16] N. Quentin, R. Perrin, C. Martin, C. Joubert, B. Lacombe and C. Buttay, "GaN active-clamp flyback converter with resonant operation over a wide input voltage range," PCIM Europe 2016; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Nuremberg, Germany, 2016.
[17] H. Fan and H. Li, "High-frequency transformer isolated bidirectional dc-dc converter modules with high efficiency over wide load range for 20 kVA solid-state transformer," in IEEE Transactions on Power Electronics, vol. 26, no. 12, pp. 3599-3608, Dec. 2011.
[18] Fan and H. Li, "High frequency high efficiency bidirectional dc-dc converter module design for 10 kVA solid state transformer," 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Palm Springs, CA, 2010, pp. 210-215.
[19] Zhang hang, Xiao Huafeng and S. Xie, "A zcs current-fed half-bridge converter with asymmetrical pwm operation," 2008 IEEE Power Electronics Specialists Conference, Rhodes, 2008, pp. 3437-3443.
[20] H. Fan and H. Li, "High-frequency transformer isolated bidirectional dc–dc converter modules with high efficiency over wide load range for 20 kVA solid-state transformer," in IEEE Transactions on Power Electronics, vol. 26, no. 12, pp. 3599-3608, Dec. 2011.
[21] C. S. Leu and Q. T. Nha, "A half-bridge converter with input current ripple reduction for dc distribution systems," in IEEE Transactions on Power Electronics, vol. 28, no. 4, pp. 1756-1763, April 2013.
[22] C. S. Leu and M. H. Chen, "Asymmetrical half-bridge converter with input current ripple reduction," 2014 International Conference on Intelligent Green Building and Smart Grid (IGBSG), Taipei, 2014.
[23] C. Marxgut, F. Krismer, D. Bortis and J. W. Kolar, "Ultraflat interleaved triangular current mode (TCM) single-phase PFC rectifier," in IEEE Transactions on Power Electronics, vol. 29, no. 2, pp. 873-882, Feb. 2014.
[24] B. R. Lin and Chia-Hung Chao, "Interleaved ZVS dc/dc converter with high input voltage," 2012 IEEE International Symposium on Industrial Electronics, Hangzhou, 2012, pp. 360-365.
[25] W. Meesrisuk, N. Sarasiri and A. Jangwanitlert, "Ripple current reduction using interleaving technique for three-level ZVZCS dc-dc converter," 2016 IEEE Region 10 Conference (TENCON), Singapore, 2016.
[26] Rong-Jong Wai and Rou-Yong Duan, "High step-up converter with coupled-inductor," in IEEE Transactions on Power Electronics, vol. 20, no. 5, pp. 1025-1035, Sept. 2005.
[27] T. J. Liang, S. M. Chen, L. S. Yang, J. F. Chen and A. Ioinovici, "Ultra-large gain step-up switched-capacitor dc-dc converter with coupled inductor for alternative sources of energy," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 59, no. 4, pp. 864-874, April 2012.