Research :: Research Highlights
Distributed Control of FREEDM System, Dr. Mo-Yuen Chow
November 19, 2009
The objective of this project is to design and implement distributed controls to achieve real-time intelligent power allocation of the grid and power management for local consumers in FREEDM system. The system will be able to achieve global optimal power allocation under local constraints. Problems such as arbitrary and partial information patterns for the local controller and dynamic network topologies will be considered in this project. A prototype of FREEDM system is shown in the figure. A communication and control network will be integrated into the power grid. To accomplish the balance of supply and demand of the power grid under communication, economic and power quality constraints, the distributed control agent embedded in each SST will calculate the system state and optimal control actions based on available power generation capacities from distributed generations and dynamic power demand from the local consumers. The distributed control agents will also schedule smart loads by using Distributed Energy Storage Devices (DESD) as buffers to smooth the burst power demand. The global power supply capacity will be expanded by integrating Distributed Energy Resources (DER) and DESDs into the power grid with the distributed control algorithms.
Comprehensive Dynamic Battery Modeling and SoC, SoH and SoF Estimation for PHEV applications, Dr. Mo-Yuen Chow
November 16, 2009
The objective of this project is to develop a comprehensive battery model for PHEV applications to accurately reflect and predict a battery's performance under different dynamic loads, environmental conditions, and battery conditions. It is achieved through identifying model parameters online based on in-situ battery measurements including the effects of various factors on a battery's performance, such as aging, temperature, humidity, usage pattern, etc. Appropriate State of Charge (SoC), State of Health (SoH), and State of Function (SoF) measures for ATEC and FREEDM applications will be defined so as to enable additional control over the battery's charging/discharging process. This will reduce the risk of overcharge and undercharge, prolong the longevity of the battery, manage the battery to its optimal usage, increase its efficiency, and also enable vehicle to grid (V2G) and vehicle to home (V2H) applications fitting the future smart grid environment.
High-performance, low-cost lithium-ion batteries, Dr. Xiangwu Zhang
November 5, 2009
High-performance, low-cost lithium-ion batteries, which simultaneously have high energy density, reduced cost, and improved abuse tolerance, are being developed based on nanofiber electrodes prepared by electrospinning. The nanofiber electrode structure can allow the electrodes to withstand repeated cycles of expansion and contraction. The nanofiber structure can also provide a controlled electrode-electrolyte interface and, hence, high rate capacity and good low-temperature performance capability. The figure shows that these nanofibers have significantly higher capacities than graphite electrodes used in current lithium-ion batteries.
Generation I Solid State Transformer (SST)
October 23, 2009
The goals of this project are to develop the Silicon IGBT based Generation I Solid State Transformer (SST) designed for 20kVA with input 12kV ac single phase and dual single phase output of 120V and single output of 240V between line-line. The Gen-I SST topology chosen consists of three modular ac-dc rectifier and isolated dc-dc converter stages, with a single dc-ac inverter stage. We got 6.5kV, 25A Si-IGBT dies and 6.5kV, 50A Si-diode dies from ABB and re-package these devices (with the help from Aegis Technologies Inc.) in an H-bridge for the high-voltage ac-dc rectifier stages and high-voltage input bridge of dc-dc converter stages of the SST. The high-frequency transformer design is a challenge due to both high frequency and high-voltage isolation. The expected efficiency of the Gen-I SST is around 92% based on device losses, HF transformer losses and input and output filter losses. The center is exploring other approaches that will result in higher efficiency. In the future (Gen-II to Gen-IV), the center will use revolutionary SiC and GaN transistors to improve the efficiency.
First Generation Communication Backbone for FREEDM System
October 23, 2009
The primary objective of this project is to establish the first generation distributed, communication platform for FREEDM, based on IEC 61850 and DNP3, which are the most widely-used and most recent standards/specifications for power or utility systems. In this platform, we plan to setup 2 IEDs and 2 computers (with wired and wireless access). Many technical and engineering issues will be evaluated and identified in this project, including communication interface between an off-the-shelf computer and embedded systems like IEDs, Linux-based operating systems and drivers, underlying protocols (such as Ethernet, IEEE 802.11, ZigBee 802.15.4, etc), upper-layer communications (IEC 61850 and DNP3), sanity check of specifications and functions, and baseline performance evaluation.
Energy Management System for PHEV Municipal Parking Deck
October 23, 2009
The goal of this project is to develop a plug-in hybrid electric vehicle intelligent energy management (PHEV IEM) system to facilitate charge control of a large number of PHEVs located at a parking deck. On the vehicle-charger side, the project deals with integrating relevant battery information such as state of charge, temperature, voltage, current, and subsequent estimation of battery state of health and condition. Mathematical models of batteries (Ni-MH and Li-ion) will be used in order to design and test charging algorithms to enable optimal charging of batteries for different battery types, conditions, and levels of charging. On the utility - charger side, the project involves the design of a supervisory control and data acquisition (SCADA) system with a controller that performs real time optimization for allocation of power and resources (e.g. bandwidth) to the chargers with the multiple constraints (user preferences, level of charge, total available power, number of cars connected etc) in consideration. This project also involves the evaluation and development of communication system architecture for the charging station.
The 2010 FREEDM Annual Conference and NSF Site Visit will be held May 18-20 at Florida State University in Tallahassee, Florida!
©2009 NSF FREEDM Systems Center