Sensorless Control of a Bidirectional Boost Converter for a Fuel Cell Energy Management System

Abstract

Fuel cells have the potential to provide clean power for a variety of uses including stand-alone residential power. But to increase the acceptance of fuel cells for off-grid generation, the cost of the energy management system must be greatly reduced. Of the many ways to accomplish this, this paper looks at reducing cost through topology changes and elimination of current sensors. A dual 2.5kW non-isolated bidirectional boost converter is designed and analyzed. The various bidirectional boost topologies are compared on cost and ability to meet the specifications. A sensorless average current mode is designed, implemented and verified through testing in a low-cost fixed-point DSP. Both boost and buck modes are accurately modeled and voltage and current controllers are designed for good closed-loop response. The accuracy of the sensorless average current measurement is investigated in both modes of operation. A classical dual-loop controller is implemented in boost mode with the sensorless average current and in buck mode, a dual controller operating in either current or voltage mode is implemented. The design is verified through testing in boost and buck mode and it is shown that the results are acceptable.