Key Takeaways & Executive Findings
- •• • The PEMFC stack exhibits a voltage swing from 213 V to 323 V and output current up to 697 A at 87.965 kW rated power, necessitating a converter with wide input range and high current handling capability; the proposed three-phase parallel quasi-Z-source topology reduces per-phase current stress by a factor of three, directly mitigating switch overcurrent risk and improving system reliability. • • Traditional interleaved parallel structures degrade ripple suppression at high voltage gain, but the proposed quasi-Z-source network with three-phase interleaving achieves low input current ripple without relying solely on large electrolytic capacitors, which are prone to aging (capacitor aging cited as a key failure mode in fuel cell systems, with lifetime impacted by ripple), thereby extending fuel cell operational life. • • The two-stage architecture (DC-boost + inverter) with a parallel battery energy storage (Vbat) on the DC bus addresses the slow dynamic response (second-level) of PEMFCs, preventing overload and load shedding during grid disturbances; this hybrid configuration ensures DC bus voltage stability under complex grid conditions. • • The proposed converter achieves high voltage gain at lower duty cycles and reduced turns ratios compared to conventional boost converters, as evidenced by the quasi-Z-source network's inherent boost capability; this reduces the voltage stress on power devices and allows the use of lower-rated, cost-effective IGBTs, improving overall system economics for high-power hydrogen fuel cell grid integration.
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Abstract
Existing grid-connected converter systems for hydrogen fuel cells suffer from insufficient voltage step-up capability, weak ripple suppression, and elevated switch overcurrent risk. This paper proposes a three-phase parallel quasi-Z-source two-stage DC-boost hydrogen fuel cell grid-connected converter (TPPQZSTSDBHFC-GCC). A mathematical model of proton exchange membrane fuel cell (PEMFC) output voltage, current, and power is established to reveal the power-voltage-current relationship and response characteristics. Based on the fuel cell output characteristics, the TPPQZSTSDBHFC-GCC topology is proposed, and its operating principle and ripple suppression capability are analyzed in detail. Results demonstrate that the proposed topology achieves high voltage gain while maintaining low ripple, low overcurrent risk, and superior steady-state performance. Simulation and experimental verification confirm the correctness and effectiveness of the proposed topology. The system addresses the critical challenge of wide-range voltage fluctuations (213–323 V) and high output currents (up to 700 A) in high-power PEMFC stacks, enabling safe grid integration and extended fuel cell lifespan.
1. Introduction
Hydrogen fuel cell grid-connected power generation is a critical pathway for hydrogen energy utilization, yet high-power proton exchange membrane fuel cells (PEMFCs) exhibit highly nonlinear volt-ampere characteristics, low output voltage, high current, and significant fluctuations. These traits render direct connection to loads infeasible; dedicated DC-DC converters and inverters are required for power conditioning. Existing research has largely overlooked the operational characteristics of fuel cells, resulting in suboptimal power generation and compromised system reliability. Specifically, conventional single-stage boost converters suffer from insufficient voltage gain, weak ripple suppression, and elevated switch overcurrent risk, which are exacerbated by the wide voltage range (213–323 V) and high currents (up to 700 A) of practical PEMFC stacks.
To address these bottlenecks, this paper proposes a three-phase parallel quasi-Z-source two-stage DC-boost hydrogen fuel cell grid-connected converter (TPPQZSTSDBHFC-GCC). The topology integrates a three-phase interleaved quasi-Z-source network with a two-level inverter and LC filter, supplemented by a battery energy storage system on the DC bus to buffer the slow dynamic response of the fuel cell. By establishing a mathematical model of the PEMFC output characteristics and analyzing the operating principle of the proposed converter, this work demonstrates that the topology achieves high voltage gain, low input current ripple, and reduced switch current stress. Simulation and experimental results validate the effectiveness of the proposed solution, offering a robust technical pathway for safe and efficient hydrogen fuel cell grid integration.
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JIANG Fei, TANG Hao, MAIMAITIAILI Wufuer, HUA Dong, HE Guixiong, GAO Jiayuan (2026). Three-Phase Parallel Quasi-Z-Source Low-Ripple High-Gain Grid-Connected Converter for Hydrogen Fuel Cells. Acta Energiae Solaris Sinica. https://doi.org/10.19912/j.0254-0096.tynxb.202608_9670
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Frequently Asked Questions
What specific failure mechanisms in PEMFCs are mitigated by the proposed converter's ripple suppression?
High current ripple accelerates degradation of the PEMFC membrane and catalyst layer, leading to reduced lifespan. The proposed three-phase interleaved quasi-Z-source network reduces input current ripple without relying on bulky electrolytic capacitors, which are prone to aging (as cited in capacitor aging studies). By minimizing ripple, the converter directly addresses the primary failure mode of fuel cell systems—capacitor aging and membrane degradation—thereby extending operational life.
How does the two-stage architecture with battery storage ensure DC bus voltage stability under grid faults?
The PEMFC exhibits a slow, second-level dynamic response, making it vulnerable to grid disturbances. The parallel battery energy storage (Vbat) on the DC bus provides rapid active power support, compensating for the fuel cell's sluggish response. This hybrid configuration maintains DC bus voltage within tight limits during load transients or grid faults, preventing overload and load shedding, as demonstrated by the system's ability to handle voltage fluctuations from 213 V to 323 V.
What are the scalability bottlenecks for high-power applications beyond 87.965 kW?
Scaling to higher power requires increasing the number of parallel phases or upgrading semiconductor ratings. The proposed three-phase parallel quasi-Z-source topology is modular; additional phases can be interleaved to further reduce ripple and share current. However, at higher power, the parasitic inductance and capacitance of the interleaved layout become critical, potentially affecting ripple cancellation. Thermal management of IGBTs and diodes also becomes challenging, necessitating advanced cooling solutions. The use of wide-bandgap devices (e.g., SiC) could mitigate these issues but at increased cost.
How does the cost of the proposed converter compare to conventional boost converters for fuel cell applications?
The proposed converter uses a quasi-Z-source network with six inductors, six capacitors, and six diodes per phase, plus three IGBTs, which is more complex than a single-stage boost converter. However, the reduced voltage stress on switches allows the use of lower-voltage-rated IGBTs, which are cheaper. Additionally, the elimination of large electrolytic capacitors (required in conventional designs for ripple suppression) reduces maintenance and replacement costs. The overall system cost may be comparable or lower when considering the extended fuel cell lifespan and improved reliability.
What empirical evidence supports the claimed low overcurrent risk in the proposed topology?
The three-phase parallel configuration divides the total input current (up to 700 A) equally among three phases, reducing per-phase switch current to approximately 233 A. This significantly lowers the overcurrent stress on individual IGBTs compared to a single-phase boost converter handling the full 700 A. The quasi-Z-source network also provides inherent shoot-through immunity, preventing catastrophic overcurrent events. Simulation and experimental results confirm stable operation under rated conditions, with switch currents well within safe operating limits.
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