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Fuel Cell Converter. For Residential Application. Brian Mathis: BSEE, May 2001 Nick Schroeder: BSEE, May 2001 JasonWoodard: BSEE, May 2001. 2001 Future Energy Challenge Objectives. Input: 48-72 VDC Output: 120 VAC 60 Hz 1.5KW Supply: Chemical Fuel Cell
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Fuel Cell Converter For Residential Application Brian Mathis: BSEE, May 2001 Nick Schroeder: BSEE, May 2001 JasonWoodard: BSEE, May 2001
2001 Future Energy Challenge Objectives • Input: 48-72 VDC • Output: 120 VAC 60 Hz 1.5KW • Supply: Chemical Fuel Cell • Use: Residential back-up power at low cost
Design Goals • Sustain continuous 1.5 KW output • Operating efficiency of 90 % • Less than 5% total harmonic distortion • Modular design for a wide range of power needs • Protection against over current, over temperature, shorts, over/under Voltage and loss of power source • Easily and safely used by non-technical personnel
What is a “Fuel Cell” • Converts Hydrogen to electricity using a chemical process with no combustion. • Can be used in a variety of applications. 1) Used by NASA since the 60’s. 2) Transportation : Auto, Air, Train. 3) Industrial/Residential Use.
Advantages of Fuel Cells • Independent power supply. • Environmental friendly, low to zero emissions. • Customized to individual needs. • Can use a variety of fuels, hydrogen, diesel, biomass etc.
Power Conversion Process DC to DC DC to AC Fuel Cell 48-72VDC Battery Bank 72 VDC Transformer Residential Applications
DC to DC BOOST CIRCUIT • Takes a variable 48 to 72 volt DC input from the fuel cell. • The boost circuit raises the DC voltage from the fuel cell to that of the battery bank. • Uses adjustable duty ratio signal to control boost circuit. • The feedback controlled duty ratio maintains the output of the circuit at a steady 72+ volts DC.
Complications • Converter components capable of handling 30+ amps • PSpice simulation • Data sheets • High voltage to drive the gate • Feedback control
DC to AC INVERTER • Takes a 72+ volt DC input. • Uses Pulse Width Modulation to drive inverter circuitry. • Inverter takes a DC input and converts to a 60hz 60 volt AC output. • 1:2 transformer increases voltage to 120 volt AC for residential use.
Complications YES
Complications • Dead time - RC • MOSFET Driver overheating • Used both P and N type MOSFETS • Signal generation • Circuit output signal noisy – led to inverter malfunction
Further Improvements • Project is an ongoing success • Use voltage regulators • Isolated sources to independent gate circuits • Improved snubber circuit on MOSFET to improve efficiency • Decrease voltage ripple on DC to DC output • Voltage equalizers between batteries • Scaleable up to 10kW
Learned Lessons • Division of labor, diverse tasks • Plan ahead, always order extra parts • Always have backup schemes • Time Management • Design before building • Communication