The 8th Annual

NC State University

Undergraduate Summer Research Symposium

 

NSF FREEDM Systems Center REU abstracts


Abstracts are listed in alphabetical order by the last name of the corresponding author.

 

 

 

 

 

 

 

Student Author(s): 

Crumpler, Matthew T.

Home Institution:

Western Kentucky University

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

NSF FREEDM Systems Center

Research Mentor(s): 

Subhashish Bhattacharya/Electrical and Computer Engineering

Anand Ramamurthy/Electrical and Computer Engineering

Title of Presentation:

A Graphical User Interface to Control MPPTs for Scalable Photovoltaic Power Systems

 

From houses and hybrid vehicles, to satellites and Martian rovers, photovoltaic power systems and infrastructure are growing to be an increasingly vital resource for today’s technology. Due to variations in light, temperature, and other factors, solar power systems can experience fluctuations in output power that can greatly affect non-intelligent storage devices.  To combat this issue, one can integrate more intelligent and controllable equipment, such as maximum power point trackers.  A maximum power point tracker (MPPT), is a highly efficient DC to DC converter,  programmed with algorithms, using various programming languages ,to determine the optimum output power, and raising or lowering output voltage(V) and/ or current (I) accordingly to a load best for a specific system. Since some systems may need to be expanded or decremented, a MPPT must be able to adapt and account for the change in input wattage and/ or the addition or subtraction of final storage devices. To simplify the programming process, one can develop a graphical user interface to communicate between the MPPT and the user. A graphical user interface (GUI) uses images and graphics rather than text commands or code to allow people to interact with electronic devices, with little to no programming knowledge needed for the final user. This way, a user can easily change variables such as output voltage or current, without the use of complicated code, making the system conveniently scalable. Meaning that, solar panels and/or batteries can be added or removed, without the need to reprogram the system’s power point tracker. This therefore allows systems to adapt to expanding projects and their requirements.  

 
 
 
 
 
 






 

 

Student Author(s): 

Emly, Alexandra C.

Home Institution:

University of Florida

Program:

NSF FREEDM Systems Center REU

College:

Textiles

Department(s):

Textile Engineering

Research Mentor(s): 

Xiangwu Zhang/Textile Engineering

Shuli Li/Textile Engineering

Title of Presentation:

Anode Materials for Lithium-Ion Batteries

 

 

 

As the world continues its efforts to “go green” transportation still remains one of the biggest obstacles to overcome in reducing carbon emissions.  Research on lithium-ion batteries is incredibly promising for the use in hybrid vehicles.  Lithium-ion batteries have excellent capacity, are lightweight, and store energy efficiently.    Electrospinning is a technique that produces nanofibers that can be used as electrodes in batteries.  An aluminum collector and a polymer-based solution contained within a syringe act as either side of a potential, and when a high voltage is applied, the solution is drawn out of the syringe and collected onto the aluminum.  This creates nanofibers which work well for energy applications because of high surface areas.  Graphite is one of the most commonly used anode materials for lithium-ion batteries; however, for technology to advance, new, better materials must be developed with higher energy storage capabilities.  Tin oxide is promising as an anode material because of its high theoretical specific capacity (781 mAhg-1) as opposed to graphite (372 mAhg-1).  A higher theoretical capacity means better energy storage, higher capacities, and higher energy density.  However, tin-based materials do undergo volume expansion and contraction during the lithium intercalation and de-intercalation.  By using nanofibers, this volume change is minimized because of the porous nature of the nanofibers.  After synthesizing three different polymer solutions with varying percentages of tin (IV) acetate, the material is electrospun and then heat treated first in an oxygen (air) environment to stabilize the material, and then in an argon environment to carbonize.  This final material can then be used as an anode material for batteries. 

 

 

 

 

Student Author(s): 

Fregosi, Daniel J.

Home Institution:

NCSU 

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

Future Renewable Electric Energy Delivery and Management Systems Center 

Research Mentor(s): 

Subhashish Bhattacharya/Electrical Engineering

Xiaohu Zhou/Electrical Engineering 

Title of Presentation:

Controlling the Inverter Stage of the Solid State Transformer 

 

 

With the increasing affordability and demand for renewable energy sources it is apparent that they have the potential to supply a significant portion of the US's energy needs.  In the meantime, while gasoline prices fluctuate, plug-in electric vehicles are becoming a clear option for the future of transportation.  The question arises: how can these distributed sources and storage devices be optimally interfaced with the electric grid?  This question is the focus of the Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center.  A cornerstone for the FREEDM Center's solution is the Solid State Transformer.  The SST is designed to replace the existing 60 Hz transformers.  The advantages of using the SST over the existing transformers are that: the power flow from a house to the grid is controllable with the SST, the power quality is close to perfect with the SST, and the transformer is much smaller with the SST because of its high frequency switching.  The SST consists of three stages: an active rectifier to convert 12kV ac to a high voltage dc bus, a dual active bridge to step down the dc voltage across an isolation transformer, and a 2-phase voltage source inverter to create the 120V and 240V, 60 Hz voltages that are commonly used in homes.  The portion of the project that I investigated this summer is the controller for the inverter.  By researching past work and running simulations in Matlab Simulink, a controller was developed.  The goal for the controller is to be able to regulate the output voltage and resist disturbances at high frequencies.  As the bandwidth of the controller is increased, the switching frequency on the inverter may be increased while component sizes may be decreased.  These changes will result in a better power quality and a higher efficiency for the inverter.  

 

 

 

 

Student Author(s): 

Hill, Lamar R.O.

Home Institution:

NCSU 

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

Computer Engineering

Research Mentor(s): 

Alex Q. Huang/Electrical and Computer Engineering

Zhigang Liang/Electrical Engineering

Title of Presentation:

Direct Current Circuit Breakers for Protection of SST Bus

 

 

The power distribution system is being revolutionized by the aimed use of Solid State Transformers (SST).  These portable transformers are smaller and lighter than the transformers currently used in the power grid, possess the capacity to regulate a variety of input voltages, and are plug-and-play integrated.  Of heightened importance is the protection of the low voltage DC bus within the SST from excessive currents.  When there is a fault in the SST Bus, the capacitor’s discharge current is extremely high and can cause system damage.  This can happen when there is a short circuit in the DC delivery cable.  Mechanical Direct Current Circuit Breakers were proposed for protecting the system from this excessive discharge current.  A simulation was constructed to study the fault current rising rate of a 2 millifarad (mF) capacitor in the 400-volt DC bus.  The SST Bus was set up as an LC Circuit to model a 5 foot wire.  The capacitor discharges current into the circuit, causing system error, 40 times faster than the DC Circuit Breaker can trip and seal off the discharge current.  Thus, while highly capable of halting excessive currents, the mechanical direct current circuit breaker is not fast enough to provide protection for the SST Bus.  Unless instantaneous direct current circuit breakers are designed, it will be necessary to use solid-state devices to protect the SST Bus from over-current.  Solid-state devices, while more expensive, provide faster fault interrupting and fault current limiting.  They are also more reliable, capable of prolonged use and intelligent power control.

 

 
 
 
 
 






 
 
 
 

 

Student Author(s): 

Radovanovic-Rivas, Ines M.

Home Institution:

Florida International University

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

Electrical and Computer Engineering

Research Mentor(s): 

Subhashish Bhattacharya/Electrical and Computer Engineering

Babak Parkhideh/Electrical and Computer Engineering

Sercan Teleke/Electrical and Computer Engineering

Hesam Mirzaee/Electrical and Computer Engineering

Title of Presentation:

Comparing Battery and Supercacitor Storage Systems to Solve the Problem of Renewable Sources of Energy

 

 

 

Energy storage systems have been in existence for a long time in many forms and applications. But now, due to an ongoing paradigm shift in power system structure and the transportation industry, they are becoming much more important. Renewable sources of energy like wind, solar, and tidal wave are penetrating into power system at a faster pace due to soaring oil prices and growing environmental concerns. The major drawback of the former is that renewable energies are not dispatchable due to their inherent intermittency and unreliability. Therefore, if proper measures are not taken, their output power will be cyclic, fluctuating and non-sustainable. The problem with the latter, i.e., Electric and Hybrid Electric Vehicles, is that if the energy/power is not coming from the fossil fuel, then it should come from another sustainable source for the time period needed. As a viable solution to the aforementioned problems, energy storage systems alongside power electronic converters are used to either make up for lapses of power/energy or assist in providing power/energy. In this study, the basics of power electronics are understand through modeling and experimentation. Along with the combined focus in comparing battery and supercapacitor types of storage systems based on their latest electrical characteristic and performance. The batteries studied includes: Lead-Acid (PbA), Nickel Metal Hydride (NiMH), Nickel Cadmium (NiCd), Sodium Nickel Chloride (ZEBRA Ni-NaCl2), and Lithium-Ion (Li-ion). Batteries from different manufacturers together with the latest supercapacitor technology in the market are evaluated based on their capacity, sustainability in power/energy, impact on environment and recycle capacity, life-cycle, and price. The information obtained will demonstrate which type of battery will be suitable for which type of generation profile such as wind, solar or tidal. Ultimately we can conclude that the solution is an integration of a battery along with a supercapacitor.  

 

 

 
 
 
 






 
 
 
 
 

Student Author(s): 

Watterson, Jason E.

Home Institution:

NCSU

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

Future Renewable Electric Energy Delivery and Management 

Research Mentor(s): 

Srdjan Lukic/Electrical and Computer Engineering

Arvind Govindaraj/Electrical and Computer Engineering

Title of Presentation:

Improving Motor Drive Efficiency in PHEVs

 

 

 

With the prices of fossil fuels rising and reserves depleting, a renewable, affordable, and practical solution must be reached.  The increasing demand for such an option has spurred tremendous growth in hybrid and plug-in hybrid electric vehicles (PHEVs).  One such aspect of this growth is research into the motor drive controller that controls regenerative braking and the transfer of that stored energy back into the vehicle’s drivetrain.  In an effort to better improve efficiency in future motor drives, a specialized test setup was built using two motors, one as the source and one as the load, with a motor drive controller for each motor.  The power generated by the load motor is fed back into the source motor, via a DC-DC converter, reducing power consumption.  As the device is running, each motor can be fine tuned to a desired speed, allowing complete control.  This controllability enables numerous tests that will provide feedback on information such as instantaneous efficiency and total power consumption.  This information can be used to derive ways in which motors can be more efficiently used in PHEVs.

 

 

 
 
 
 






 
 
 
 
 

Student Author(s): 

White, Felicia N. 

Home Institution:

Philander Smith College 

Program:

NSF FREEDM Systems Center REU

College:

Engineering and Technology

Department(s):

Future Renewable Electric Energy Delivery and Management 

Research Mentor(s): 

Srdjan Lukic/Electrical and Computer Engineering 

Title of Presentation:

Modeling Electric Vehicles 

 

 

Electric vehicles are the future of automobile production and consumption in the United States and throughout the world. Although electric vehicles (EVs) benefit the environment by not releasing any gasoline emissions, considerations such as high initial costs, limited battery capabilities, and limited driving ranges prevent many consumers from purchasing them. For this reason, researchers are continuously making an effort to develop new ways to improve the vehicles in order to reduce production costs and increase operation efficiency which will make the EV even more appealing to potential consumers. Creating a model in SimDriveline, an application of Simulink in MATLAB, allows various fast and easy evaluation of the performance of various vehicle designs and configurations while saving the time and money it would cost for physical experimentation. In this research I have produced a simulation of an electric vehicle by replacing the gasoline engine with an electric motor and battery in order to find which battery type worked best in the vehicle model.  

 

 

 

 

 

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Last modified July 2009 by Sharon E. Hunt