Islanding of

Large Scale Power Systems

Wenxin Liu, Sanjeev Srivastava,

Bhuvana Ramachandran,

Li Liu, Qunying Shen,

Zhiping Ding, and David Cartes

Center for Advanced Power Systems (CAPS)

Florida State University

Tallahassee, FL 32310 USA

Funded by the:

Department of Energy

Office of Naval Research

Power Systems Islanding

Power systems may become unstable during severe faults when operated close to stability limits.

Defensive islanding intentionally split an interconnected power system into islands to prevent the further

spreading of wide area blackouts.

After islanding, power system is running in a less versatile and degraded state, but catastrophic losses

can be avoided.

Existing islanding algorithms are based on simplified power system data and necessary load shedding

information can not be provided

Background

How Did We Get Into

Intelligent Defensive Islanding

Possible impacted

region

Actual island

What is the problem?

Power systems are operating closer to

stability limits. Unexpected events

(hurricanes, earthquakes, terrors, etc.),

system failures, human errors, etc. may

cause catastrophic failures.

What is the solution?

To avoid wide area blackout and minimize

losses, defensive islanding intentionally

splits power systems into islands to block

faults from spreading.

What are we doing?

We are working on intelligent control based

optimal splitting strategies of large scale

power system to get efficient solutions in

real time.

IEEE 39-bus New England System two or three islands

What is It

39

1

2

30

9

3

8

7

6

5

4

25

18

17

27

11

12

10

32

14

15

26 2938

28

1624

2336

2122

35

33

19

20

34

13

31

37

Reserve: Generation(I) / Load(I) 0

Linear Load Flow: Optimize I=YV, st. g(x)=0

Coherency

Load Generation Dispatching: C

Particle Swarm Optimization (PSO)

PSO algorithm is a relatively new collaborative computation technique first proposed by Kennedy and Eberhart in 1995

PSO is simple in concept and computationally efficient

Our Approach

1 1 2 2( ) ( )i i p i g iv w v c rand x x c rand x x

i i ix x v

sk

vk

vpbest

vgbest

sk+1

vk+1

sk

vk

vpbest

vgbest

sk+1

vk+1

AMPSO - An illustrative example

WECC 9-bus Power System

Background

2 397

5 6

1

4

8

80

170 0 100 0 95

120

0

85

Solution

Vector:

Line No.:

1 1 1 1 0 1 1 1 0

1-4 2-7 3-9 4-5 4-6 5-7 6-9 7-8 8-9

An AMPSO based islanding algorithm is proposed that improves the efficiency of the PSO and BPSO based

algorithms.

The algorithm can find the optimal solution for small scale power systems and is very computationally efficient to find

good candidate solutions for larger scale power systems.

Using reserve and seeking generation groupings using slow coherency, the algorithm can split a given power

system into desired number of stable islands quickly

efficiently.

Necessary load shedding and generation dispatching information can be provided in addition to information

about which transmission lines to open.

What We Learned We Can Do What We Learned We Can Do

But the Future Grid looks Like This

2015 and Beyond

What We Learned Is Hard

(and we still need to address) Simple islanding schemes LIKE dispatchable generation and consistent

Loads.

Hard to find economic/clean solutions, sa. reserve w/ AMPSO & slow coherency over other methods. Everything is treated like base load.

Simple islanding schemes DO NOT LIKE distributed intermittent, non-dispatchable sources.

Asynchronous generator reclosure, nuisance tripping, over voltage, back-feeding, endangering line workers.

Simple islanding schemes DO NOT LIKE Unspecified, intermittent loads:

Finite inertia issues, overvoltage , undervoltage, low power instability.

Simple islanding schemes DO NOT LIKE multiple IOUs:

Are there market solutions that can help make islanding solutions.

Consortium for

Energy Distribution Automation Research

Summary - Accomplishments

We developed:

AMPSO with Slow Coherency Island finding method.

Non-linear fault diagnostics for distributed sensor faults.

Dynamic Load shedding approach using expert system theories.

Real time PSO and it was just published in Engineering Applications of Artificial Intelligence, patent pending.

An Intelligent Auction Scheme for Smart Grid Market using a Hybrid Immune Algorithm to be published in Transactions of Industrial Electronics, patent pending.

Table Top Test Bed

Thank You

Please Remember

Jack Crow

and

Ken Lively

What would they say of CAPS today?

From Ken Lively

Focused My EMS Vision

Control development is going to distributed, fault tolerant supervisory control.

Distributed sub systems are by function, e.g. electrical, cooling, lube oil system.

Intelligence is being pushed to the lowest component levels.

Dependencies among systems and functional boundaries are being minimized.

In order to reduce cost, the technology is going from redundant systems to distributed systems. Only critical systems will have redundancy.

To improve accuracy of decision making, missing values or states of the system should be based on measurements from nearby sensors and inferred from calculations.

The focus of our research should be to put together a demonstration system of the control system for electrical system and other functional systems (weapon power, chilled water,

etc.) based on agents.