1. IEEE Chapter Symposium
Possible Applications of PMUs for Detecting Angle Instability in Power Systems
Nima Farkhondeh Jahromi Zongyu Liu
March 28, 2017

2. Angle Stability Classification First Proposed PMU-Based Algorithm
Outline
Problem Formulation
Angle Stability Classification
First Proposed PMU-Based Algorithm
Second Proposed PMU-Based Algorithm
Conclusion and Remarks
March 28, 2017

3. Contradictory combination
Problem Formulation
Centralized Power plants
Small number of large scale gen. units
Traditional generator design/const.
Not so high efficiency
Popularity of renewable energy
Large number of small scale gen. units
Newer Technology in generator design
Higher efficiency
Power networks (due to power transfer capacity) get closer to their stability margin
Less tolerance
Regulated electricity market
Deregulated electricity market
Various power flow directions
More congestions
Contradictory combination
Stability control (instability detection) is (will be) the key challenge
March 28, 2017

4. [Real-time] small disturbance angle stability assessment
Angle Stability Classification [Real-time] Angle Stability Assessment in future Power Systems
Axis 1
[Real-time] large disturbance angle stability (transient stability) assessment
Axis 2:
[Real-time] small disturbance angle stability assessment
March 28, 2017

5. 1st Proposed PMU-based Algorithm
Detection of transient instability based on the real-time COA
Concept of Centre Of Angles (COA)
Difficult to directly measure
Difficult to access in real time. Number of units being dispatched can vary
March 28, 2017

6. 1st Proposed PMU-based Algorithm (1)
Substitution of the internal angle with the phase angle of the high side bus voltage
Substitution of the inertia time constant with the high side active power injection G T
Phase Measurement Unit (PMU)
Approximation! (could be a source of error)
March 28, 2017

7. 1st Proposed PMU-based Algorithm (2)
Illustration of substitution of the inertia time constant with the high side active power injection
March 28, 2017

8. 1st Proposed PMU-based Algorithm (3)
Real-time Centre of Inertia for area i
Real-time Centre of Inertia for the whole system
March 28, 2017

9. 1st Proposed PMU-based Algorithm (4)
Taking the appropriate remedial action(s) based on the value of
If > “pre-specified benchmark” (continuously)
1) Area i (in a detailed analysis each gen. can be an area) is speeding up
2) Suitable remedial action is to trip some generators
If < “pre-specified benchmark” (continuously)
1) Area i (in a detailed analysis each gen. can be an area) is slowing down
2) Suitable remedial action is load shedding
March 28, 2017

10. 1st Proposed PMU-based Algorithm (5)
Alarm mode based on comparing the real-time signals
A real-time signal for area i
A signal to be used as a reference: Critically-stable response
March 28, 2017

11. 1st Proposed PMU-based Algorithm (6)
Rescue-time definition
Permanent decline
March 28, 2017

12. 1st Proposed PMU-based Algorithm (7)
The method (the reference signal) is fault-location (and also fault-type) dependent.
The method is dependent on the inertia time constant of the generators (Perhaps in future; lighter machines have higher output)
March 28, 2017

13. 2nd Proposed PMU-based Algorithm
Principal idea is to have a real-time energy function (by means of PMUs) for a system divided into two clusters.
The main question: Based on the real-time energy function, will the system split to more clusters or not?
Area 1 M1 ω1
Area 2 M2 ω2
New [temporary] steady-state
March 28, 2017

14. 2nd Proposed PMU-based Algorithm (2)
March 28, 2017

15. Conclusion and Remarks
It might be possible to perform an on-line transient instability detection and mitigation for a multi-area power systems
By improving (generalizing) the proposed algorithm, it might be possible to avoid some blackouts happen due to islanding
Designing the appropriate remedial action, is very much dependent on the system capabilities and is difficult to be generalized
March 28, 2017

16. Discussions Suggestions Questions Criticisms Ideas Compliments
March 28, 2017