Transactions of China Electrotechnical Society  2024, Vol. 39 Issue (18): 5755-5767    DOI: 10.19595/j.cnki.1000-6753.tces.231074
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High-Conversion-Ratio Low-Ripple Isolated DC-DC Hydrogen Converter Based on Stacked Filter Structure
Liu Haijun1,2, Zhang Li3, Zhang Qiaogen1, Han Minxiao3
1. School of Electrical Engineering Xi’an Jiaotong University Xi’an 710049 China;
2. State Key Laboratory of Advanced Power Transmission Technology State Grid Smart Grid Research Institute Co. Ltd Beijing 102209 China;
3. School of Electrical and Electric Engineering North China Electric Power University Beijing 102206 China

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Abstract  

Hydrogen energy is an important energy storage method in the future renewable energy power system, and the hydrogen converter is a key device connecting the power system and electrolyzer. The primary task of the hydrogen converter is to provide high current, low voltage DC power to facilitate hydrogen production in the electrolyzer. However, the continuous impact of the output current ripple from the hydrogen converter on the internal components of the electrolyzer leads to a shortened lifespan and reduced efficiency in hydrogen production. Consequently, design requirements for hydrogen converters in these applications typically encompass low current ripple, cost-effectiveness, high efficiency, and high voltage conversion ratio.
This paper proposes a novel high-conversion-ratio low-ripple isolated DC-DC hydrogen converter, utilizing a stacked filter structure. The Stacked Filter Structure Circuit (SFSC) is implemented in parallel with the output side of the converter to actively compensate for output current ripple, enabling zero-current ripple output regardless of the filter inductance, switching frequency, and duty cycle. The SFSC, a simple soft-switching circuit, exhibits low power consumption characteristics. To enhance the output current capability, an interleaved parallel Buck circuit is employed on the output side of the converter. This circuit employs a half-wave conduction control method, effectively improving the voltage conversion ratio of the converter without requiring additional components.
The proposed hydrogen converter topology utilizes an isolated transformer T1 with a center tap. The primary side of the transformer is connected to a full bridge circuit, converting the DC voltage Vin into an AC voltage. The duty cycle of the full bridge circuit is 0.5, and the switching frequency is fH. The secondary side of the transformer consists of a two-phase interleaved Buck circuit and a parallel circuit with SFSC. The two-phase interleaved Buck circuit serves to further reduce the voltage and increase the output current level. The two-phase interleaved circuit adopts half-wave conduction control, meaning that SP1 is only turned on during the conduction period of S1, and SP2 is only turned on during the non-conduction period of S1. The PWM signals of SP1 and SP2 have the same duty cycle DP and switching period TP. In order to maintain current symmetry in the two-phase parallel circuit, the switching frequency fP of SP1 and SP2 needs to be set as an even multiple of fH. The SFSC is connected in parallel with the output side of the two-phase interleaved Buck circuit, which consists of only AC current with no DC component. In this circuit, CS、SC1、SC2, and LC form a loadless Boost circuit, wherein the switching transistor SC1 replaces the traditional freewheeling diode in the circuit. By utilizing the switching action of SC1 and the conduction of its anti-parallel diode, capacitor CS can achieve charging and discharging, overcoming the issue of conventional Boost circuits being unable to operate under loadless conditions.


This paper provides a detailed theoretical analysis of the proposed hydrogen converter topology, control method, parameter selection, and performance. The analysis is supported by simulations and experimental prototypes. The results show that the SFSC accounts for less than 2% of the total power loss and significantly reduces the output current ripple of the hydrogen converter. By using half-wave conduction control, the voltage conversion ratio of the hydrogen converter can be increased by a factor of 4N compared to traditional full bridge converters. In future research, further modular design of the proposed hydrogen topology can be explored, aiming to build high-power multi-port hydrogen converters. Additionally, improvements can be made to the stacked filtering circuit structure and control strategies to suit modular design requirements better.
Key words： Hydrogen converter      stacked filter structure      isolated DC-DC      low output current ripple      high voltage conversion ratio     
Received: 09 July 2023     
PACS: TM46  
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Liu Haijun
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Cite this article:   
Liu Haijun,Zhang Li,Zhang Qiaogen等. High-Conversion-Ratio Low-Ripple Isolated DC-DC Hydrogen Converter Based on Stacked Filter Structure[J]. Transactions of China Electrotechnical Society, 2024, 39(18): 5755-5767.
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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.231074     OR     https://dgjsxb.ces-transaction.com/EN/Y2024/V39/I18/5755
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