More Related Content Similar to lakshitha weerasinghe Similar to lakshitha weerasinghe (20) 1. Emerging Scenario with Renewable Energy in Sri Lanka.
Meeting the Challenges in Power System
Operations & Economic Consequences.
Lakshitha Weerasinghe
Ceylon Electricity Board
2. ∗Basics of Power System Operations in
the Sri Lankan context.
∗Understanding the problem!
∗Solutions!
Contents
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
3. Basics of Power System Operations
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
4. Time Line of activitiesGenerationPlanning
Constructionof
GeneratingAssets
Constructionof
Transmission
Infrastructure
UnitCommitment
Freq.Control
Transmission
Planning
EconomicDispatch
Supply-Demand
Balancing
SecondsMinutesHrs./ Days
GovernorAction
Years
OperationsPlanning
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
5. Time Line of activities
UnitCommitment
Freq.Control
EconomicDispatch
Supply-Demand
Balancing
SecondsMinutes
Hrs./ Days
GovernorAction
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
9. Frequency (Hz)
Power (MW)
50Hz
100 MW
49.5Hz
110 MW
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
Supply-Demand
Balancing
Seconds
GovernorAction
MinutesHrs./ Days
10. Freq. Error
Without Governor Control
With Governor Control
Frequency
50 Hz Time
Disturbance (Generator Trips!)
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
Supply-Demand
Balancing
Governor
Action
12. Frequency
50 Hz
Freq. Error
With Frequency Control
Time
Disturbance (Generator Trips!)
With Governor Control
(Primary ALFC)
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
13. Bringing Frequency back to 50Hz.
Hydro*
Thermal
CEB 1361 MW
•CEB 1164 MW
•IPP 771 MW
*Note :- Mini Hydro and wind not included
14. Understanding the Frequency Controller
0MW 67
Kothmale single unit maximum
capacity = 67MW
Eg.
50
49 51
5248
Hz
30 60
50Hz
51Hz49Hz
Demand Generation
50Hz
51Hz49Hz
Demand
Generation
50Hz
51Hz49Hz
Demand Generation
Any one of the following power
stations is assigned at any given time
to look after the system frequency.
1. Victoria (unit size = 71MWx3)
2. Kothmale (Unit size x 67 x 3)
3. New Laxapana (50MW x 2)
4. Samanala Wewa (60MW x 2)
© Lakshitha Weerasinghe Ceylon
Electricity Board 2014
15. Time Line of activities
UnitCommitment
Freq.Control
EconomicDispatch
Supply-Demand
Balancing
SecondsMinutes
Hrs./ Days
GovernorAction
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
16. ∗Economic Dispatch – What load to be
kept on each machine that is already in
operation.
∗Unit Commitment – What are the
machines to start or stop to serve load
within a given period.
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
17. Other Constraints/ Considerations
(1) Hydro Power comes last in the water
utilization Priority order
1. Water Service and Drainage
2. Environment
3. Irrigation
4. Power
(2) Pond balancing
(3) Reservoir Operations
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
18. Annual Inflow 3500 GWh
Annual Hydro Generation 3500 GWh
Spill
MOL
Storage Capacity ≅ 1250 GWh
Reservoir1
Reservoir7
20. Resource Attributes that causes problems
to System Operations
Small Hydro Non Dispatchability.
Wind Non- Dispatchability and Intermittency.
Solar Non-Dispatchability and Intermittency.
Problems associated with Non
Conventional Renewable Technologies.
Over 260 MW of Small NCRE generators are connected to the Distribution network.
They appear as “Negative Loads” to system operators.
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
24. 20:00
16:00
12:00
08:00
04:00
00:00
24:00
Load MW
© Lakshitha Weerasinghe Ceylon
Electricity Board 2014
Issues due to non Dispatchable nature
3 Base Load Coal plants. Minimum stable load is
180MW.
Base Load Thermals such as Sapugaskanda HFO
plant, CC plants.
Frequency Controlling Hydro Plant
Plants providing (Up/Down) Operating Reserves.
“Must Run” Hydro plants
Hydro plants operated to balance ponds.
360MW of non dispatchable small renewable
plants.
25. © Lakshitha Weerasinghe Ceylon Electricity Board 2014
Issues due to Intermittency
Technical
• Violation of operating frequency
limits. (±1%)
• Operation of Under Frequency Load
Shedding (starting from 48.75Hz).
• Severe Frequency instabilities leading
to cascaded total collapse.
Economical
• Cost of maintaining high spinning
reserve.
• Underutilization of energy from other
sources which may be cheaper or at
zero cost (such as from Run-of-the-
river plants that are spilling).
• Cycling of base load thermal plants.
26. How Intermittent is Wind SPEED ?
0.00
2.00
4.00
6.00
8.00
10.00
12.00
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Velocitym/s
Seasonal Variation of Wind Velocity
8.80
9.00
9.20
9.40
9.60
9.80
10.00
10.20
10.40
1 2 3 4 5 6 7 8 9 101112131415161718192021222324
velocitym/s
Diurnal Variation of Wind Velocity
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300 350 400 450 500
Source: SEA
27. © Lakshitha Weerasinghe Ceylon Electricity Board 2014
How Intermittent is Wind Power ?
Minute to Minute variation of out put (MW) of a wind Farm over
3 hour period.
28. © Lakshitha Weerasinghe Ceylon Electricity Board 2014
How Intermittent is Solar?
Perfect Solar Day Pre-monsoon Clouds Passing Over
Source - SEA
29. Cost of Spinning Reserves.
Gradient = Incremental cost Rs/kWh
Generation
Cost per
hour
Output (MW)
No Load
Cost per
hour
Plant No Load Cost per Hour
(Rs million)
(September 2014)
Kalanitissa CCP (Diesel) 1.17
AES CCP 1.3
Kerawalapitiya Yougadanavi 1.6
Victoria 10 m3 /s (25% of full load )
© Lakshitha Weerasinghe Ceylon Electricity Board 2014
30. © Lakshitha Weerasinghe Ceylon Electricity Board 2014
Cost of Cycling
Plant Start/Stop Cost (Rs million)
Hot (<8 h) Warm
(8<h<48)
Cold
(48<h)
Kalanithissa CC
(Diesel)
3.9 4.6 5.3
AES CC 3.3 8.6 10.5
Kerawalapitiya
Yougadanavi
5.9 7.1 9.5
32. © Lakshitha Weerasinghe Ceylon Electricity Board 2014
Solutions
Supply Side Solutions
• Maintaining larger spinning reserve to do Load-Frequency Control on supply side.
• Operating intermittent sources (such as Wind) below capable output and utilize the balance
capacity to cushion out fluctuations at the source itself.
• Group Control & AGC at Load dispatch Centre.
• Secondary Automatic Load-Frequency regulation using Integral Controllers.
Demand Side Solutions
• Valley Filling measures to improve Low demand period
• Introducing variable loads to be called upon low demand periods.
• Changing Customer demand using smart Grid options.
• Introducing local loads such as Hydrogen, Compressed Air and Battery technologies to utilize
part of the generation to cushion out intermittency/variability at the terminal.
Other Solutions
• Forecasting Wind speeds to do improved Operations Planning.
• Interconnect with neighboring Grids.
• Geographical scattering of Wind and Solar park locations.
