Reduction of low-frequency current ripples in fuel cell power conditioning systems using proportional-resonant control

The control methods used to reduce low-frequency current ripples in fuel cell power conditioning systems are discussed. The concept of minimized impedance design for the flow of harmonic currents in the energy storage branch is proposed since it can help improve the system dynamic response and harmonic absorption. The effects of different control strategies (including single voltage loop, single current loop and outer-voltage inner-current control loop) on the output impedance are evaluated and compared. Furthermore, proportional-resonant controllers are introduced to generate extremely low impedance for harmonic currents at specific frequencies. The theoretical analysis and control strategies are verified by simulation results.