Kyle Merkert ECE 791/792 Senior Design Project October 2009 – May 2010 Faculty Advisor: Dr. Wayne Smith

Introduction We depend on electricity but we use a system that often involves long distance distribution rather than localized power:

Introduction Power distribution as it is today isn’t always reliable.

Problem Statement My solution is a high power inverter for producing a sine wave at 110V RMS from electricity stored in 12V batteries.

Design Goals  At least 400 Watts Output Power  Integrated Overload Protection Circuits  Sine Wave Output with < 10% THD  Smooth Switching Between Grid and Inverter  Informs User of Errors and Warnings  Able to Power Inductive Loads

Design Considerations Step up voltage before or after forming sine wave? This implementation steps up voltage first, then uses a network of transistors to create a sine wave with this high voltage input.

Design Considerations This alternate implementation creates a sine wave with the 12 volt input and then steps up the voltage with a high power transformer.

Design Considerations Sine wave production: Pulse Width Modulation (PWM) or Digital to Analog Conversion (DAC)? PWM DAC

Implementing/Testing Plan 1. Protective circuitry 2. Microprocessor programming for 60Hz sine wave output 3. Amplitude adjustment 4. Voltage step-up experimentation 5. Error reporting and increased current capabilities 6. Final user interface and load control

Budget (High Estimate)  Deep Cycle Batteries$200  High Voltage Capacitors$40  Power Transistors$50  Power Resistors$10  Misc. Parts as Needed$100  Unexpected Costs (Damaged Parts, Etc.)$100 Total Cost (High Estimate):$500

Design Goals By Month November:  Decide on PWM or DAC.  Program sine wave output of microprocessor.  Experiment with stepping up voltage and determine if sine wave should be formed before or after voltage step-up. December:  Build protection circuits.  Construct first prototype of inverter for very low load conditions.  Build amplitude regulation circuit.  Program power monitoring of grid power.  Complete progress Report

Design Goals By Month January:  Add error reporting circuits.  Increase output power capabilities.  Optimize THD of sine wave to resistive loads. February:  Maintain sine wave with inductive loads.  Determine maximum safe output power.  Program software to prevent loads from drawing too much power.

Design Goals By Month March:  Add user interface: Battery life and power usage monitoring. April:  Finish and optimize anything that does not meet design goals.  Prepare UNH-URC Poster Presentation May:  Have finished product completed  Prepare and present final report