Date of Award

6-2012

Degree Name

MS in Electrical Engineering

Department

Electrical Engineering

Advisor

David B. Braun

Abstract

Cal Poly’s ongoing Energy Harvesting from Exercise Machines (EHFEM) project is a very convenient and cost-effective way for generating DC power from physical exercise and sending it back to the electrical grid as AC power, providing a renewable energy source for the future. The EHFEM project consists of numerous subprojects involving converting different types of exercise machines for power generation. This project is a continuation of one of the previous subprojects, specifically involving an elliptical machine, and focuses on improving system functionality at different machine settings without altering the elliptical user’s experience by selecting a new DC-DC converter design, while keeping the other system components intact. The new proposed DC-DC converter design is based on a non-isolated, PWM-switching single-ended primary inductor converter (SEPIC) topology, as opposed to the resonant zero-current switching/zero-voltage switching (ZCS/ZVS) topology-based off-the-shelf DC-DC converter that the previous project utilized, which had poor system functionality at high physical input levels (greater than 30V input) from the elliptical trainer. This project proves that a PWM-switching SEPIC topology provides a functional DC-DC converter design for DC power generation and inverter interfacing from a dynamic input voltage generator because of its wide input voltage range, high power driving capability and inherent voltage step-up and step-down functions. The proposed DC-DC converter supplies up to 288 watts of power and outputs 36 volts, and simultaneously takes 5-65 volts from its input depending on the elliptical user’s physical input level. This project details the new DC-DC converter’s design and construction processes, compares its topology to other existing DC-DC converter topologies and analyzes unfeasible designs as well as the overall system’s performance when converting the generated DC power to AC power, and documents any potential problems when used for this specific application.