Floating voltage fuel cell drive system

Fuel cell technology, with its advantages of high energy density, fast refuel, and possibility to produce from renewable energy, becomes a promising solution for electric vehicles. However, the output voltage of fuel cells is variable (up to 30%) with the load current. Thus, a conventional fuel cell drive system requires a two-stage converter topology with a ‘constant voltage’ DC bus in between.  The first-stage is a DC-DC converter to regulate the output of the fuel cells to the constant DC voltage. The second-stage is a 3-phase DC/AC drive inverter to generate AC power for the motor. The DC voltage is usually maintained by Li-ion batteries. The capacity of the batteries depends on the power matching of the fuel cells and the motor.

The technical challenges to be addressed in the project include: (1) how to maintain the required power output of the motor with the floating DC voltage; and (2) how to dimension the energy storage for given fuel cell power and motor power.



Yujing Liu (contact)

Professor vid Chalmers, Electrical Engineering, Electric Power Engineering

Qian Xun

Doktorand vid Chalmers, Electrical Engineering, Electric Power Engineering



Gothenburg, Sweden

Volvo Cars

Göteborg, Sweden


Swedish Energy Agency

Funding Chalmers participation during 2018 with 499,850.00 SEK

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Project Web Page at Chalmers


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