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CIGRE Working Group (WG) C4.603:
“Analytical techniques and tools for power balancing assessments”
• Main objective: Critical assessment of existing modelling methods and tools for analyzing power balancing issues in order to provide recommendations for future developments
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WG C4.603: Analytical techniques and tools for power balancing assessments
Scope of work• Power balancing includes all power system control and
operational aspects ranging from secondary (active) power control up to management of reserves and intra-hour power (balancing) markets.
• Relevant application areas for the analytical techniques and tools in question include the analysis of:– Secondary and tertiary control (active power balance)– Reserves management (how to assess the need for
reserves)– Benefits and challenges with larger control areas and
multi-national balancing markets.
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WG C4.603: Analytical techniques and tools for power balancing assessments
Background / motivation• Two main drivers are influencing operation of the transmission systems:
– Rapid development of wind power– Opening to competition of regional electricity markets as part of larger power
markets crossing national borders and interconnections.
• Creating new challenges in predicting power flows and managing imbalances and congestions in the transmission networks.– increasing challenges related to balancing control and management of fast
reserves.– Few tools and analytical techniques readily available for the analysis of power
balancing issues, ranging from secondary and tertiary generation control to the organisation of markets for balancing and reserves management.
New methods and analysis tools are therefore needed to address the new challenges in transmission system operation.
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WG C4.603: Analytical techniques and tools for power balancing assessments
Main activities• Overview of balancing control practices and balancing markets.
– This activity will serve as an introduction and a background for identifying the need for new analytical tools.
– Previous and ongoing work under study committees C1, C2, C5 and C6 may provide valuable input to this overview.
• Review existing analytical techniques and tools for the assessment and analysis of balancing control problems.
• Collection and description of relevant application examples.
• Identify and describe the need for new models and tools based on existing knowledge.
• Recommend areas for further research and development to gain new knowledge.
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First meetings
– Minneapolis, July 25 (IEEE PES GM)
– Paris, August 25, (Cigre Session)
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Balancing and reserves - overall aim :• Balancing: Control and stabilise the power system subject to:
– variable and uncertain (renewable) power generation, – matching a variable and uncertain demand,– and managing outages/contingencies (N-1,..)
• Tools are needed to: – Identify the requirement for reserves– Quantify the need for control in terms of
• Power capacity (MW)• Energy / duration (MWh)• Response time
– Design and analyse the performance of the control systems– Analyse the additional cost of balancing
6
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Preliminary thoughts on how to identify and describe tools:• How can we classify the different “balancing” problems that
needs to be analysed?• How can we classify the different tools?• Can we summarise the findings of the WG in a table:
And by this identify the need for further developments (new models and tools)
7
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ProblemsTools and methods
?
Tasks and time-scales in operation
8
Increasingly market based -Long term markets
and contracts-Day-ahead markets
- Primary frequency control- Inertia
- Intra-day markets- Real-time balancing markets (tertiary contr- AGC (secondary control)
Degree of automation
sec. min. hour day week month/year
Main challenge due to increased variability (wind power in particular)
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Tasks and time-scales in operation
9
Increasingly market based -Long term markets
and contracts-Day-ahead markets
- Primary frequency control- Inertia
- Intra-day markets- Real-time balancing markets (tertiary contr- AGC (secondary control)
Degree of automation
sec. min. hour day week month/year
Main challenge due to increased variability (wind power in particular)
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Power system simulators Market models, Unit committment, ..?
10
Example: Analysis tool developed from power system simulators
• A method for analysis of primary and secondary control• The fast dynamics in the power system is neglected• The focus is the dynamics in the minute area
8 000
10 000
12 000
14 000
16 000
18 000
20 000
22 000
6:00 7:00 8:00 9:00 10:00
Tid (h)
Last
(MW
)
ProduksjonLast + utveksl.
Time (h)
ProductionLoad + exchange
Stepwise Power Flow (SPF)
Control stages in power system operation
50.0
R∆f
50.1
0.0
49.9
Frequency [Hz]
Reserves activated [MW]
Time0 1 min. 15 min. 1 hour
System frequency bias / response: B = [MW/Hz]∆P∆f
∆f
∆P
Primary Secondary Tertiary
12
Frequency control in the Nordel power system
50.1
50.0
49.905:00 05:30 06:00 06:30 07:00 07:30 08:00
Frequency (Hz)
Time
Scheduled (according to day-ahead market)
Frequency control (balancing)
Primary control response
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∆P = ∆Pwind(t) - ∆Pload(t)
∆f = ∆P / B(δ)∆Pgen = f(δ, ∆f)
Unit/load droops
∆f < ∆flim => RP
Power flow
t = t+1
Pload(T), Pgen(T)Pload(T+1), Pgen(T+1)Unit/load droops, δi
Frequency Bias, B(δ)Regulating power (RP)
Implementation of SPF model for the study of primary and secondary control behaviour
Sum of unit droops, διFrequency bias, B [MW/Hz]
14
Load increaseRegulating power activated at 30 min
49.85
49.90
49.95
50.00
50.05
50.10
50.15
0 10 20 30 40 50 60
Tid (min)
Frek
vens
(Hz)
0
2000
4000
6000
8000
10000
12000
14000
16000
0 5 10 15 20 25 30 35 40 45 50 55 60
Tid (min)
Regu
lers
tyrk
e (M
W/H
z)
Example: Analysis tool developed from market models
- Day-ahead disptach
- Resourceredispatch
Reserve requirements- Control area- Balancing area- Total area
System imbalance- Demand forecast error- Wind forecast error
- Water values- Area prices
Syst
em
bala
ncin
g
Res
erve
pr
ocur
emen
t
- Reserve procurement cost- Availability of regulating reserves
- System balancing cost- Regulating resource exchange
- Total production cost- Optimal generation dispatch- Transmission dispatch
Input:
Step:
Output:
- Water values- Area prices
- Plant description- Production costs- Transmission system
- Demand, Ex-&Import curves- Hydro inflow, wind speeds
Day
-ahe
ad
mar
ket
EMPS or PSST IRiE
Flow based Power-market Simulator
IRiE – Integrated Regulating power market in Europe15
Wind power variations
• Characteristic of wind power variations:– High amplitude low
frequency variations– Lower amplitude high
frequency variations
• Uncertainty of wind power related to the variability
• Different solutions are needed to balance wind
Apt, J., The spectrum of power from wind turbines, Journal of Power Sources, 2007
Day (100%)
Hour (30%)
Minute (7.5%)
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Secondary/tertiary control Example on balance management
NO1
DK1SE
Germany800/1200 MW
DK2
+/-1000 MW
670/630 MWData for DK1, west Denmark 2003 MW
Central power plants 3,516
Decentralised CHP units 1,567
Decentralised wind turbines 2,374
Offshore wind farm Horns Rev A 160
Maximum load 3,780
Minimum load 1,246
• January 8, 2005 a strong storm crossed over Denmark
• The wind farms of western Denmark at first produced close to rated power, but then started to cut out due to the excessive wind speed (+ 25 m/s) – the wind production were reduced from about 2200 MW to 200 MW in a matter of 10 hours
AC
DC DC
The case demonstrates that the existing real-time balancing market can handle large variations in (wind) generation and demand
8 January 2005
-1000-750-500-250
0250500750
1000125015001750200022502500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
MW
h/h
Exchange DK1 -> NO1Balancing power (NO1)Windpower DK1
Source: NORDPOOL
20
Norwegian hydro as the European energy battery – potential and challenges
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Offshore load
Wind farm
Grid 1
Grid 2
An early stage senario for offshore Multi-terminal HVDC System
Control and stability of MTDC grids?
Primary and secondary control?
How to exchange balancing services?
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Report content (first outline)1. Introduction
• Motivation for the work• Scope
2. Power balancing assessments• Main definitions (what do we cover how do we define the different terms)• Balancing control problems (Define and classify the different “balancing”
problems that needs to be analysed)3. Analytical techniques and tools
• Description of available tools and analytical techniques• Overview and classification of the tools (e.g. in a table)
4. Recommendations• Identify and describe the need for new models and tools based on the findings
above (and summarised in the table)• Recommend areas for further research and development to gain new
knowledge5. Conclusions and references 22
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