Design of a high efficiency converter for fuel cell

applications

Vaal University of Technology

Energy Postgraduate Conference 2013

Christian Kuyula

Outline

• Introduction• Fuel cell converter• Converter design process• Hardware tests • Performance results• Summary

[1] Source: The fuel cell review industry 2012

Fuel cell powered mine locomotive prototype launched by Anglo American Platinum in partnership with Ballard (May 2012) [1]

“South Africa is in a unique position to reap significant benefits from a local fuel cell market… Fuel cell demonstration projects are under way around the country and it has the necessary manufacturing and engineering expertise. The window of opportunity to make it happen is now.” — Cynthia Carrol, former CEO of Anglo American.

Introduction

Fuel cell converter

DC-DC converter purpose:

●The converter is aimed to handle a wide range of input voltages and efficiently convert the unstable electrical voltage generated by a fuel cell into usable power for equipment operating on DC.

●The converter is key to prolong the a fuel cell’s life and improve its reliability.

Voltage and current characteristic of a fuel cell [2]

[2] S. Ang & A. Oliva, Power-Switching Converters, 3rd ed. Boca Raton: CRC Press. 2011

Interleaved synchronous buck converter

Additional Switch Q2 in case of Synchronous Buck Converter

Control

VIN

Switch NodeLOUT

COUT

VOUT

D1Q2

Q1

Conventional Buck Converter

Control

Non-synchronous vs. synchronous buck converter

2 phase interleaved synchronous buck converter

Converter design process

SpecificationsSpecifications

Webench® Designer

Webench® Designer

CircuitSimulation

CircuitSimulation

ConverterconstructionConverter

construction

PrototypecompletionPrototypecompletion

Hardwaretesting

Hardwaretesting

SpecificationsInput voltage: 22-46

VOutput voltage: 13.8

VOutput power: 100 W

High Efficiency > 85%

Hardware tests Oscilloscope

DC source

PIC microcontroller

DC-DC converter

(DUT)

MOSFET and resistors mounted on a bread board

Step load transient

response test

Turn-on input voltage test

Performance results

Vin Iin Pin Vout Iout Pout Efficiency

22 0.935 20.57 13.7 1.4 19.18 9322 1.852 40.744 13.59 2.8 38.052 9322 2.744 60.368 13.51 4.2 56.742 9422 3.669 80.718 13.47 5.6 75.432 9322 4.595 101.09 13.4 7 93.8 93

Vin Iin Pin Vout Iout PoutEfficienc

y46 0.46 21.16 13.7 1.4 19.18 9146 0.89 40.94 13.65 2.8 38.22 9346 1.35 62.1 13.6 4.2 57.12 9246 1.78 81.702 13.5 5.6 75.6 9346 2.2 100.98 13.48 7 94.36 93

Summary• Since the fuel cell market in South Africa as well as the technical expertise on

fuel cell ancillary technologies are currently gaining momentum, this research addresses the need for an efficient fuel cell converter providing usable DC current.

• An interleaved synchronous buck converter was used for the project. Design process steps, hardware tests and performance results were presented. The converter module enables regulation of a single high-current voltage (13.8 V @ 7 A) directly from a wide input voltage ranging from 22 to 46 V. The efficiency of the module was found to be superior to 90%.

• Much is needed to educate and prepare the general public for this established technology option.

Thank you!