Center for Energy Systems Research

 

 

 

Aging Testbed and Sensor Development

Efficient use of disposable resources in a power system contributes to Smart operation of a grid. Condition based rather than age based use of resources such as distribution transformers requires accurate knowledge of leftover age and inclusion of appropriate sensors. Experiments have been conducted at Tennessee Tech to develop ageing guidelines for the distribution transformers based on IEEE standards. Accelerated ageing tests and optical sensors for furanic compounds (2-FAL) in the insulating oil are being pursued. Loss of life as a result of short term overloads on a distribution transformer in a smart grid could then be evaluated.

 

Electrical Substation Testbed

At the Smart Grid Laboratory, the Electrical Substation Testbed (Figure 1) allows real-time simulations of power systems with hardware in-the-loop, such as protective relays and communication devices. The Electrical Substation Testbed is based on the state-of-the-art digital signal processing technology, by non-real-time and real-time simulators. In the computer real-time simulation, the power system is carried out with digital real-time simulation of the electric power system, reproducing the voltage and current waveforms, with the desired accuracy that are representative of the behavior of the real power system being modeled.

The Electrical Substation Testbed has five rack panels with a computer real-time simulator, satellite synchronize clock, communication processor, protective relays, and relay test systems (Figure 2). Smart grid applications are explored by using protection, control, communication and measurement functions of protective relays. Protection, control and communication systems for electrical substations can be evaluated for large power systems by using the computer real-time simulator. Actually, an adaptive overcurrent protection for a microgrid based on programmable logic and math operators has been performed, by validating the selectivity, speed and reliability. In the future, we want to upgrade our Electrical Substation Testbed with a Synchrophasor and SCADA system that will be applied in power system control and monitoring activities for research and education.

 

Laboratory Research Capabilities

Presented here is a brief bullet list of research capabilities utilizing the smart grid laboratory.

• Power grid emulation
  • Study propagation of disturbances
  • Study synchrophasors on power grid testbed
  • Study intelligent means of recovering from faults, i.e. self-healing
• Solar Emulators
  • Study grid stability due to intermittency
  • Study non-inertial effects on grid behavior
  • Study synthesis of inertial effects
  • Study reactive power synthesis in inverter design
• Wind Emulators
  • Study grid stability due to intermittency
  • Study reactive power effects and synthesis
• Islanding mitigation/prevention
• Island creation
• Load shedding
• Protection
• Frequency Control
• Intelligent automatic generation control with high penetration of renewables
• Microgrids
• UAS charging/autonomous navigation/inspection

 

A series of example project will give ideas as to the types of projects that can be conducted in this laboratory.

Example Project: Cascading Failure Prevention

A power grid such as the one shown in Figure 6 was created in the laboratory. A Transmission line failure was emulated by closing a switch feeding one of the transmission lines. Figure 7 shows the resulting currents in the transmission line after the failure, a subsequent transmission line failure, and successful power redistribution due to intelligent agents which changed phase angles of generators relative to each other until no transmission lines were overloaded.

Example Project: Preventative Maintenance Facilitated by UAS Inspection

An active area of research in the smart grid laboratory is autonomous inspection of power grid assets for preventative maintenance purposes. The image on the left showing the warmth of a substation transformer under normal operating conditions with no abnormal hot spots.

• Autonomous navigation
• Self-Charging (From the power line or special docking stations along the line)
• Inspection (optical techniques, rf techniques, machine vision techniques),

Example Project: Reactive power strategy testing

A student tested a strategy for reactive power compensation utilizing wind speed as the trigger for engaging banks of capacitors. In the example the initial wind is zero and once a threshold wind is met the turbine engages. It also has a very high speed wind disengage self-protection mechanism which is evident near the end of the test run where it disengages at very high speed wind and then reengages once the wind drops below the threshold. This capacitor engagement strategy works well in the middle of the test but does nothing for the dynamic engage, disengage portions of operation. Of course an algorithm based on reactive power needs, not wind speed is clearly required.

Example Project: Load Shedding

A student using two generators and the wind turbine emulator created a scenario where the load profile was too much for the total generation available and implemented a prioritized list of loads that could be shed. It is interesting to note that the fluctuations all were in the traditional generators and that the wind power was utilized throughout the study.

Note also that the dynamics caused by the load shedding are often greater than the step changes in load giving incentive to find less aggressive solutions to power shortfalls. Perhaps the rolling brown outs in California are implemented with less severe transients.

Example Project: Testing inverter design for solar emulator to a step change in load

A student developed inverter was tested using the solar panel emulator as a power source. The AC side of the microgrid was subjected to a step change in load so that the stability of the inverter could be assessed. The GUI shows a brief spike in voltage and a step change in current as a load is turned off.

Example Project: Voluntary Customer Load Shedding through Smart Phone App

Visiting student scholars from Annamalai University in India wanted to do a small demonstration project using our laboratory. A phone app was mocked up (didn’t have time to actually write the app) whereby if a utility/customer agreement was in place, voluntary load shedding could be implemented by the utility indicating a high demand time and the consumer responding by turning off some of their loads. The smart meter can be used by the app to let the consumer know how much power they turned off and potential rewards for actively participating.