14pesgm2488 - IEEE Power and Energy Society

1
Issues Affecting Anti-Islanding Detection
in Power Systems with High Wind
Penetrations and Low Inertia
Dr Robert Best
EPIC Research Cluster, Queen’s University Belfast
[email protected]
energy, power
& intelligent control
2
Introduction
• Irish Experience
• Loss-of-Mains Detection and Power System Inertia
• Phasor Measurement Units for Loss-of-Mains
3
Ireland
• Synchronously isolated, 6.5 GW peak
• 2.5 GW installed wind (June 2014)
• 40% renewable target (2020)
• 2 HVDC links to Great Britain
• 16.5% of energy from wind in 2013
4
5
6
25-27 January 2014
Wind Gen MW
System Demand MW
5000
4000
Power, MW
3000
2000
1000
0
00:00
-1000
12:00
00:00
12:00
00:00
12:00
00:00
7
25-27 January 2014
Wind Gen MW
System Demand MW
Wind Penetration %
5000
60
50
Power, MW
3000
40
2000
30
1000
0
00:00
-1000
20
12:00
00:00
12:00
00:00
12:00
10
00:00
0
Wind Penetration %
4000
8
25-27 January 2014
Wind Gen MW
System Demand MW
E-W Interconnector
Wind Penetration %
5000
60
50
Power, MW
3000
40
2000
30
1000
0
00:00
-1000
20
12:00
00:00
12:00
00:00
12:00
10
00:00
0
Wind Penetration %
4000
9
Major Operational Issues
• Less Power System Inertia
– 50% non-synchronous limit (Wind + HVDC)
– A future 70%-80% non-synchronous limit
• Loss-of-Mains Detection
– Current rate-of-change-of-frequency (ROCOF) setting:
0.5 to 0.6 Hz/s
– Future ROCOF 1.0 to 2.0 Hz/s
• Small-signal stability
• Reactive power provision
• Ramp rates
10
Power Systems with Different Inertia
DC Interconnector between Ireland and Great Britain trips
resulting in 500 MW imbalance.
11
FSIG Wind Farm – Inertial Response
Inertial response of 26 MW wind farm
Inertia constant = 4.4 s
8.2
Power
8
50
7.8
49.9
7.6
49.8
7.4
7.2
49.7
7
49.6
6.8
25
30
35
40
45
Time (seconds)
50
55
60
Frequency (Hz)
Power (MW)
Frequency
12
DFIG Wind Farm - No Inertial Response
15.8
50
Power
49.9
Frequency
Power (MW)
15.4
15.2
49.8
15
49.7
14.8
49.6
14.6
14.4
49.5
0
5
10
15
20
Time (seconds)
28.5 MW DFIG wind farm
Inertial constant ≈ 0 s
25
30
35
Frequency (Hz)
15.6
13
Power System Inertia
Solutions:
Curtail wind and keep the synchronous machines on.
14
Curtailment
1600
Wind Production (MW)
1400
1200
1000
800
600
400
Actual Wind Output
200
0
24/12
Forecast Output
25/12
26/12
27/12
Date
28/12
29/12
30/12
15
Power System Inertia
Solutions:
Curtail wind and keep the synchronous machines on.
Emulated inertia from wind turbines, battery
storage, etc.
Load response techniques.
Even so, there will still be an increase in maximum ROCOF:
Can plant cope with these dynamics?
Islanding detection will be desensitised – will it
work?
16
Loss-of-Mains Detection (ROCOF and Vector Shift)
G59/3 – distributed generation connection in UK
“ROCOF, knock-off” (Nuisance tripping)
17
Islanding Caused by ROCOF
Major disturbance observed in GB on September 30th 2012
50.1
Flotta (Red) has
islanded from the main
system (Blue) for
approximately 10
minutes
50.05
50
49.95
49.9
49.85
49.8
49.75
49.7
49.65
49.6
5.38
5.4
5.42 5.44 5.46 5.48
5.5
5.52 5.54 5.56 5.58
4
x 10
18
Loss-of-Mains Detection (ROCOF and Vector Shift)
G59/3 – distributed generation connection in UK
“ROCOF, knock-off” (Nuisance tripping)
– With high system ROCOF no acceptable balance between
nuisance tripping and non-detection can be achieved.
Vector Shift
–
Debatable as a suitable islanding detection method.
– Given the choice DG owners tend to choose vector shift
in high ROCOF systems.
Communications based solutions using PMU are a possible
solution.
19
Phasor Measurement Units
OpenPMU and Commercial units installed.
20
Islanding Detection using PMU
21
Methods
NO TRIP
TRIP
Freq / Hz
Differential ROCOF
Reference
Local
Time / s
Maximum
Probability, %
Phase Difference
-8
-6
-4
-2
0
2
Phase Angle, degrees
4
6
8
22
Islanding Detection using PMU
The phase difference based method:
–
Eliminates nuisance tripping.
– Effectively has a non-detection zone of zero, at least in
terms of avoiding out-of-phase reclose.
Latency of internet communications within suitable range (<100 ms).
Communications based loss-of-mains requires contingency.
Phase variation is site specific.
23
Summary
High wind penetrations tend to reduce power system inertia.
This is already a concern in Ireland, and many other power
systems will follow suit.
Island detection may no longer be viable by conventional
methods.
Synchrophasors offer a solution to loss-of-mains detection.
24
Questions?
Dr Robert Best
EPIC Research Cluster, Queen’s University Belfast
[email protected]
energy, power
& intelligent control

Download Report