Ripple Reduction

Fuel cells have a maximum output current. The output current of the fuel cell should not exceed the rating due to safety and reliability concerns. Suppose there is a fuel-cell system with a 150A capability. The typical input current waveform for the Fuel-Cell with inverter load is shown in the figure below. In addition, the RMS current for the Fuel-Cell is also shown as the orange line. Notice how the RMS current is well below the 150A limit of the fuel-cell but due to the significant ripple, the RMS current cannot be increased to 150A.

We can see that when a current ripple is present, the maximum output power of the fuel cell cannot be utilized. If active current ripple cancellation is employed in the dc-dc converter system, the current ripple would look something like the green line in the figure below. As we can see, the current ripple is significantly reduced. The new RMS input current, shown in blue, is much higher than without the ripple cancellation. Therefore, almost all of the output capabilities of the fuel-cell may be utilized by the system. In addition to better utilization of system capabilities, the reduced current ripple offers better fuel cell lifetimes and fuel consumption.

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