A Novel Circulating Current Free Zero Current Switching Three-Level Resonant Composite Full Bridge Converter for New Energy Medium Voltage DC Collection System
He Xiaokun, Hu Renjie, Chen Wu
School of Electrical Engineering South East University Nanjing 210096 China
Abstract：DC converter is a key part of a medium-voltage DC (MVDC) convergence system. Its role is to convert DC power into load-required voltage or current-controllable DC power, which plays a boost, isolation, power transmission, and other functions. The research on the flow converter has always been a hot spot in domestic and foreign power electronics technology. Compared with the huge transformer in the traditional medium-voltage AC convergence scheme, the converter in the medium-voltage DC scheme can significantly reduce the size of the device due to medium and high-frequency control. With the increasing output port voltage and capacity of photovoltaic and wind power, higher requirements are placed on bridge converters with the ability to adapt to high input voltages. In order to adapt to the development trend of new energy power generation with higher and higher port voltage, this paper proposes a circulating current-free ZCS (zero-current-switching) three-level composite full-bridge converter. The converter consists of a half-bridge three-level circuit and a full-bridge circuit multiplexed with two switching tubes. The three-level circuit with a resonant capacitor will transmit 90% or more of the total power. In contrast, the auxiliary full-bridge circuit transmits the remaining power so that the voltage stress on all switching tubes is only half of the input voltage. This structure facilitates the converter to high input voltages, preserves the soft-switching characteristics of all switching tubes, and eliminates the primary-side loop current. However, since the current waveform of the converter is triangular, the peak current is high under the same transmission power, and the turnoff current of two multiplexed switch tubes is the maximum, resulting in large shutdown losses. Therefore, LC series resonance technology is introduced in the half-bridge three-level structure unit, forming LC series resonance to transmit energy to the secondary side of the transformer. With the same electrical parameters as the converter ports, the proposed converter can improve the triangular current waveform to a sinusoidal waveform. Accordingly, the peak currents of all the switching devices and the turn-off currents of auxiliary switching tubes can be reduced, which further decreases their switching losses. Through theoretical analysis, when the input voltage Vin and output voltage Vo are known, the transformer turns ratio N1 determines the power of the two transformers. Moreover, the larger N1 is, the larger the proportion of the whole power transferred by the main circuit Ptr1 is, and the smaller the power transferred by the auxiliary transformer Ptr2 is. Therefore, for the main transformer Ptr1 to transmit the majority of power, N1 should be taken large. Decreasing the blocking capacitor Cb is beneficial for reducing conduction loss but will increase its voltage peak. Therefore, the selection of Cb should be considered in a compromise. According to the requirement that the resonant frequency of the converter is greater than the switching frequency, the upper limit of the resonant capacitor value can be obtained. At the same time, the lower limit of the resonant capacitor value can be determined based on the rated power of the converter. This paper analyzes and designs the key parameters of the converter, conducts simulation verification through Plecs, and produces a 150 V/750 V/1 kW prototype for experimental verification.
何晓坤, 胡仁杰, 陈武. 一种适用于新能源中压直流汇集的无环流零电流软开关三电平谐振式复合全桥变换器[J]. 电工技术学报, 2023, 38(19): 5274-5287.
He Xiaokun, Hu Renjie, Chen Wu. A Novel Circulating Current Free Zero Current Switching Three-Level Resonant Composite Full Bridge Converter for New Energy Medium Voltage DC Collection System. Transactions of China Electrotechnical Society, 2023, 38(19): 5274-5287.
[1] 陈孝莺, 许国, 韩华, 等. 基于脉宽调制的电流断续型谐振变换器[J]. 电工技术学报, 2022, 37(24): 6252-6261. Chen Xiaoying, Xu Guo, Han Hua, et al.Dis- continuous current mode resonant converter with pulse width modulation control[J]. Transactions of China Electrotechnical Society, 2022, 37(24): 6252-6261. [2] 吴世伟, 刘文彪, 纪陵, 等. 新能源发电功率预测系统数据流容错研究[J]. 电气技术, 2018, 19(12): 107-111. Wu Shiwei, Liu Wenbiao, Ji Ling, et al.Research on data flow fault tolerance of new energy power gen- eration forecasting system[J]. Electrical Engineering, 2018, 19(12): 107-111. [3] 杨晓光, 王德鑫, 贾哲, 等. 负载和输入电压自适应零电压软开关全桥变换器[J]. 电工技术学报, 2022, 37(12): 3061-3072. Yang Xiaoguang, Wang Dexin, Jia Zhe, et al.A load and input voltage adaptive zero-voltage-switching full-bridge converter[J]. Transactions of China Elec- trotechnical Society, 2022, 37(12): 3061-3072. [4] Yin Zhijian, Chen Manxin, Li Kerui, et al.A new ZCS PWM full-bridge converter of Buck-type for applications with very high input voltage[C]//IECON 2015-41st Annual Conference of the IEEE Industrial Electronics Society, Yokohama, Japan, 2016: 1495-1500. [5] Zhang Xin, Chung H S H, Ruan Xinbo, et al. Analysis, optimized design and adaptive control of a ZCS full-bridge converter without voltage over-stress on the switches[C]//2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Expo- sition (APEC), Palm Springs, CA, USA, 2010: 1214-1221. [6] Yin Zhijian, Hu Jiefeng, Chung H S H, et al. A ZCS-PWM voltage-driven three-level converter with a secondary-side simple soft-switching snubber[J]. IEEE Transactions on Industrial Electronics, 2016, 63(12): 7542-7552. [7] Ortiz G, Leibl M G, Huber J E, et al.Design and experimental testing of a resonant DC-DC converter for solid-state transformers[J]. IEEE Transactions on Power Electronics, 2017, 32(10): 7534-7542. [8] Cao Guoen, Guo Zhicheng, Wang Yibo, et al.A DC-DC conversion system for high power HVDC- connected photovoltaic power system[C]//2017 20th International Conference on Electrical Machines and Systems (ICEMS), Sydney, NSW, Australia, 2017: 1-6. [9] 李福, 邓红雷, 张国驹, 等. 一种中间电容谐振型级联双向DC-DC变换器[J]. 电工技术学报, 2022, 37(20): 5253-5266. Li Fu, Deng Honglei, Zhang Guoju, et al.A cascaded bidirectional DC-DC converter with intermediate capacitor resonance[J]. Transactions of China Elec- trotechnical Society, 2022, 37(20): 5253-5266. [10] 王议锋, 韩富强, 杨良, 等. 一种双变压器结构的多谐振型软开关直流变换器[J]. 电工技术学报, 2019, 34(4): 738-746. Wang Yifeng, Han Fuqiang, Yang Liang, et al.A dual transformer-structured multi-resonant soft-switching DC-DC converter[J]. Transactions of China Electro- technical Society, 2019, 34(4): 738-746. [11] Suryadevara R, Parsa L.Full-bridge ZCS-converter- based high-gain modular DC-DC converter for PV integration with medium-voltage DC grids[J]. IEEE Transactions on Energy Conversion, 2019, 34(1): 302-312. [12] 朱选才, 徐德鸿, Hidetoshi Umida, 等. 应用逆阻型IGBT的移相控制电流型全桥零电流开关DC/DC变换器[J]. 中国电机工程学报, 2006, 26(12): 45-49. Zhu Xuancai, Xu Dehong, Umida H, et al.Current-fed phase shift controlled full bridge ZCS DC/DC converter with reverse block IGBT[J]. Proceedings of the CSEE, 2006, 26(12): 45-49. [13] Wang Huai, Sun Qian, Chung H S H, et al. A ZCS current-fed full-bridge PWM converter with self- adaptable soft-switching snubber energy[J]. IEEE Transactions on Power Electronics, 2009, 24(8): 1977-1991. [14] Ning Guangfu, Chen Wu, Shu Liangcai, et al.A hybrid resonant ZVZCS three-level converter for MVDC-connected offshore wind power collection systems[J]. IEEE Transactions on Power Electronics, 2018, 33(8): 6633-6645. [15] Ning Guangfu, Chen Wu.A hybrid resonant ZCS PWM converter for renewable energy sources connecting to MVDC collection system[J]. IEEE Transactions on Industrial Electronics, 2018, 65(10): 7911-7920. [16] Shu Liangcai, Chen Wu, Ning Guangfu, et al.A resonant ZVZCS DC-DC converter with two uneven transformers for an MVDC collection system of offshore wind farms[J]. IEEE Transactions on Industrial Electronics, 2017, 64(10): 7886-7895. [17] Ning Guangfu, Chen Wu, Shu Liangcai, et al.Hybrid resonant ZVZCS PWM full-bridge converter for large photovoltaic parks connecting to MVDC grids[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2017, 5(3): 1078-1090. [18] Ning Guangfu, Chen Wu, Shu Liangcai, et al.A hybrid ZVZCS dual-transformer-based full-bridge converter operating in DCM for MVDC grids[J]. IEEE Transactions on Power Electronics, 2017, 32(7): 5162-5170. [19] Chen Yu, Kang Yong, Nie Songsong, et al.The multiple-output DC-DC converter with shared ZCS lagging leg[J]. IEEE Transactions on Power Elec- tronics, 2011, 26(8): 2278-2294. [20] Chen Yu, Kang Yong.A fully regulated dual-output DC-DC converter with special-connected two trans- formers (SCTTs) cell and complementary pulse width modulation-PFM (CPWM-PFM)[J]. IEEE Transactions on Power Electronics, 2010, 25(5): 1296-1309. [21] 陈宇. 电力电子变换系统的元件复用理论与方法[D]. 武汉: 华中科技大学, 2011. [22] Pal A, Basu K.A zero-current-switched PWM full bridge DC-DC converter[C]//2019 IEEE Energy Conversion Congress and Exposition (ECCE), Baltimore, MD, USA, 2019: 6424-6429. [23] He Xiaokun, Hu Renjie, Chen Wu.A hybrid three- level ZVZCS converter for photovoltaic power con- necting to MVDC collection system[J]. Energies, 2022, 15(15): 5365.
2023, Vol. 38 
