Testbed for Generator Torque Oscillations
|Duration||Fall 2019 - Spring 2020|
|Faculty Advisor||Dr. Brian Johnson
Brian Johnson, Ph.D., P.E.
|Clients||Matchyaraju Alla / SEL
|Team Members||Zuhao Zhou
Disturbance on power systems such a faults, large variations in power generation or power consumption can cause oscillations in phase angle, frequency, voltage magnitude, which in turn combine to result in oscillations in real and reactive power generation. The response of synchronous generators can be characterized using the solution to the swing equation for most cases, which represents the angle variation for very small changes in frequency:
This is driven by the transient mismatch between mechanical input power and electrical output power and the resulting response of the electromechanical system.
- 1 Project Definition
- 2 Background
- 3 Project Obejective
- 4 Data Acqucisition System designed by 2018-2019 Senior Design Team
- 5 Hardware Devices
- 6 Testbed Design
- 7 Deliverables
- 8 Usability Test
- 9 Future Work
- 10 Team Members
- 11 Additional Documentation
Conventional wisdom is that the generator will slip a pole if the system swings any further. However, recent field data has demonstrated that the some machines have been not done so and their excitation control has pulled them back to stability.
A typical response for a stable swing would exhibit damped oscillations:
Or if we plot power versus angle:
If the system is loaded more heavily or the protection and control response is slower, the response is more severe, and the generator may near its transient stability limit:
The angle swings almost to the stability limit
Building on the data acquisition system designed by a 2018-2019 senior design team design a test bed and test plan for testing generator performance during power swings, especially those near boundary of pole slipping
(1) Learn to use the present data acquisition system, and in light of the project needs propose, design and implement modifications as needed
(2) Develop, test and implement test procedure for safely operating the generator in the appropriate operating conditions.
(3) Integrate data from all measurement devices used in a time stamped and synchronized format for post processing
Data Acqucisition System designed by 2018-2019 Senior Design Team
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We choose 18AWG cable which fusing current is 81A.This value meets our experimental requirements. Here is the link of American wire gauge.
Standard Banana Plug
We use the same brand banana plugs as those in the lab. Thus,it is more convenient when customers use or modify test beds.
Female Banana Plug
We use female banana plug to attach the plug-in signal.
The terminals easily can be re-used in the field, allowing for the replacement of wires or equipment, generally with standard hand tools. Screw terminals usually avoid the requirement for a specialized mating connector to be applied to the ends of wires.
Thank Mr.Magine (ME Workshop) for helping us make this brass adapter. It solves the trouble caused by connecting PT, but its surface is not covered by insulators, and the safety is not very high.
We use fork connectors to let hard device reach the terminal strip.
We use alligator clips to replace the mini grabber. When it is connected to a shunt resistor, the hardware can better fit the panel of the test bed.
We use a cart as a base. We put testbed, DAQ, Monitor, Desktop and CT on this cart.
We hide all the cables behind the front panel. Circuits are shown in the picture. All hard devices are designed for easy removal and installation. Thus, there will be only female banana plug on the front panel.When we use this test bed, we just need to simply use a plug cable to connect the channels to the female banana plug on the panel.
We tested DC circuit and CT shunt resistances. (Details and data is in the file below）
The DC power supply was connected between R_1 and R_3. Then, according to the testbed, a multimeter was connected to the corresponding channel interface on the front panel of the testbed to read the voltage across the resistor R_2. V_R2 represents the terminal voltage. The DC V/I circuit is connected to the DAQ device. Therefore, the DAQ device is limiting the range of the V/I circuit. The DAQ should not exceed 11V. So, we should set 10V is our max. Afterward, Wahab set a ratio to display the exact value of the terminal voltage of the synchronous machine, which is 21. We need to calculate the ratio by each test and get the average value of it. Conclusion: The value of the average ratio is 20.88 close to 21. This means the DC circuit part has the usability.
CT Shunt Resistances
The CT shunt resistance was paralleled with current transformer. Its power value does not allow us to test is with high current and high voltage. We simply use the law of resistance to measure the value, then compare the value shown by the power supply machine and the value displayed by the multimeter. Conclusion: The value of CT2 and CT3 has changed for unknown reasons. The ratio of voltage to current is an exponential function, not a proportional relationship. CT1 has usability.
1) Test the usability of I_R3 and three PTs
2) Check the continuity of the wiring(soldering part)
3) Change the heat sink which more suitable for resistances
4) Integrate data from all measuring devices in timestamp and synchronized format for post-processing