Power system security with high Power system security with high ...

Power system system security security with with high
high
penetrations of DG
Impact of the Smart Grid on Bulk System
Reliability Assessments Workshop
Image reproduced from Renewable Energy Information Office
Andrew Keane, Paul Cuffe
Electricity Research Centre
University College Dublin
8 h th December 2011

Distribution Transmission Interface
• Key y boundary y point p
– Physical
– Organisational
• Physics of the system have no respect for
organisational boundaries
• High penetrations of DG mean conventional plant
g p p
will be decommitted
– Instantaneous DG penetrations of 25% hit in Ireland

Synchronous Machine Capability
Actiive
Power (MWW)
50
40
30
20
10
0
‐35 ‐15 5 25 45
Reactive power (MVAr)
Sync
Machine

Wind Turbine Reactive Power
1
0.8
0.6
0.4
Active
Power (pu)
0
-0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5
Reactive Power (pu)
0.2

Distribution/Transmission Interface
Active Power
(MW)
50
40
30
20
10
Raw (P,Q)
99% Reliability
0
‐35 3 ‐25 2 ‐15 ‐5 5 15 225
Reactive Power (MVAr)
Cuffe, P., Smith, P. And Keane A., “Effect of Energy Harvesting Network Reactive Support on Transmission System Voltage Performance”,
CIRED, Frankfurt, June 2011

P‐Q Measurements at 110 kV Bus
1
08 0.8
0.6
04 0.4
Active
Power (pu)
0
-0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5
Reactive Power (pu)
0.2

Summary Points
• AVR capability of synchronous machines needs to
be replaced
– Detailed requirements yet to be determined
• Wind turbines have capability, but if distributed,
network impedance present limitations
• PQ capability can increase hosting capacity of
distribution networks networks or reduce losses or or….
• How can these conflicting objectives be
reconciled?

Challenges
• Enable cost effective, low loss connections for
DG
– While also providing p greactive power p where and
when it is required on transmission system
• What are the transmission requirements?
– Controlled voltages?
– Supply of reactive power?
– Fault ride through at DG level?
• Reconciliation of TSO and DSO objectives

Potential Solutions
• Increased control of distribution voltages
• New distribution and transmission planning
methods
– Reactive power margin, DG output
• Tools for operation
– Who controls P & Q?