2020 ASEE Virtual Annual Conference Content Access

At the UXX we have experienced increased student interest in alternate and renewable energy topics in Electrical and Computer Engineering over the past 5 years. This has presented a challenge, as we currently only offer a single “Electromagnetic Energy Conversion” course, which is in a lecture format with a required associated laboratory section. To address this challenge, we have been systematically phasing out older topics, i.e., D.C. motors, and adding course content relevant to photovoltaics and wind energy production. This has necessitated a redesign of some of our laboratory experiences and required us to reconsider the most efficient way to transmit a breadth of understanding while giving students the opportunity to explore selected topics in greater detail.
A fundamental building block of all photovoltaic and wind-based energy systems is the switching voltage regulator. This device enables changing system D.C. voltage levels with exceptionally high efficiencies, in many cases comparable to transformers for A.C. systems. This basic building block also appears in D.C. to A.C. conversion techniques for grid-connected devices. As a first step in updating our laboratory sequence, we elected to include material and experiments related to switching regulator design.
We have examined, and employed in past classes, commercially available switching regulator evaluation boards, and while they are quite functional, they provide limited opportunity to explore the various parameters that determine the overall design, and how controlling each parameter individually may affect the overall performance of the system. To address these limitations, this BYOE paper describes an experimental apparatus that we designed that includes the two most common building blocks: the buck regulator, and the boost regulator.
In our design, we incorporate inexpensive Hall-effect current sensors in all circuit branches, including the critical inductor and switch nodes. We also provide observability of the related node voltages. All of our signals are generated by an embedded computing device that drives a graphical user interface. This approach allows us to address several parameters that are typically not visible in commercial units. For example, the switching frequency is easily variable, allowing students to observe how this relates to concepts such as peak inductor current, peak switch current, ripple, and efficiency, all in real-time. We also allow the students to run the system in open loop mode to observe relationships between output voltage and duty cycle. A useful feature is the ability to use closed loop control, and to modify the feedback parameters in real time to study the effect on settling time and stability.
In this paper, we describe our device, and give complete design information. We also show how it may be used in various classroom and laboratory settings and adapted to different levels of course material. We also include simulation information and show how the simulations may be compared with the experimental observations. All materials are open-source and the authors will supply complete design packets.