Three-Phase Parallel Quasi-Z-Source Low-Ripple High-Gain Grid-Connected Converter for Hydrogen Fuel Cells

• • 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.