joint electra/sirfn workshop - integrated...
TRANSCRIPT
Joint ELECTRA/SIRFN Workshop
October 24th 2016, Niagara, Canada
Helfried Brunner
Technical Coordinator IRP ELECTRA
Web-of-Cells Concept and
Control Scheme
www.ElectraIRP.eu
This project has received funding from the
European Union’s Seventh Framework
Programme for research, technological
development and demonstration under
grant agreement no 609687.
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• Real-time voltage and frequency control (‘balancing’) for
the future (2035+) power system
− Novel functional architecture incl. new concepts for network
observability and robust controllers that act across different control
boundaries
Electra Scope
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• Generation will shift from classical dispatchable units to
intermittent renewables
• Generation will shift from few large units to many smaller
units
• It will shift from central transmission system connected
generation to decentralized distribution system
connected generation
• Electricity consumption will increase significantly
Trends and Assumptions
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• Large amounts of fast reacting distributed resources (can)
offer reserves capacity
• Electrical storage will be a cost-effective solution for offering
ancillary services
• Ubiquitous sensors will vastly increase the power system’s
observability
• Developments in Information and Communication Technologies
will support the pathway towards more decentralized managed
power systems
Trends and Assumptions
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Trends and Assumptions
From: Transmission grid connected dispatchable synchronous
generators with downstream power distribution
To: Large number of small intermittent RES generators that
are distributed everywhere (all voltage levels)
Increasing electrical loads (at medium/low voltage levels) and
active control of flexible loads
Reverse powerflows, local congestions, local voltage
problems
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• TSO centric + improved TSO-DSO
coordination
• Vertical Integration of horizontal
distributed control schemes
• Early consultation with ETP SG
(jul’2014)
• Do not underestimate the role of
the DSO (think beyond ‘TSO
centric and TSD-DSO coordination’)
• Emphasize role of (grid-connected) ‘microgrids’ and distributed
storage
• Think out of the box
The ELECTRA DoW Proposal
ELECTRA De-centralized Web-of-Cells (WoC) concept
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• Divide the power system (grid) in smaller entities
(geographical areas) – cells – with local observability and
control by a cell operator that is responsible for the real-time
control of the cell
− Local problems are solved locally, in a secure manner,
without system-wide communication, bottom-up aggregation and
central decision making
• Cells are connected with each other via tie-lines (one or
multiple, radial or meshed)
− Neighboring Cells can support each other in a autonomous
distributed collaborative way (adjacent central aggregation)
− Neighboring cells can decide on local activation optimization
(neighbor-to-neighbor central)
Web-of-Cells Concept
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• Cells can contain/span multiple voltage levels
• Cells are dimensioned in relation to
− Computational complexity of Detection and Resolution (secure
dispatching of reserves)
− Sufficient reserves providing resources
− Spatial correlation of weather forecasting for RES
• Cells do not need to be self-reliant for matching demand with
supply
− They may depend on structural energy imports or exports (e.g.
coming from large central RES power plants) as cleared in a
system-wide optimized setpoint calculation
− They receive a setpoint (an import/export profile) as a reference
for the real-time control (tie-line power exchanges)
Web-of-Cells Concept
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?
Web-of-Cells Concept
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• Voltage control: local by nature
− Detection is local
− Local reserves must be activated
• In each cell :
− Pilot nodes, AVR nodes with PVC (droop) control, and nodes with
discontinuous voltage regulation (e.g OLTCs)
− Post-Primary Voltage Controller (PPVC): Optimal Powerflow
Calculation (losses, security, robustness) to determine:
Safebands for pilot nodes (security and robustness)
Voltage setpoints for nodes (continuous and discontinuous)
Droop settings for AVR nodes
− Regularly updating settings based on updated cell state forecast
(proactive) or if safeband violation (corrective)
Voltage Control in WoC
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• Objective : System balance restoration (load = generation)
− frequency is just an observable …
Frequency/Balance Control Current Control Scheme
LFCA1
LFCA2
LFCA3
1. Frequency Containment Control FCC:
Frequency • Contain frequency deviation with (slow)
inertia bearing generators
• Collaborative and global
2. Frequency Response Control FRC:
Tie-line Powerflow and Frequency • Restoring system balance and
frequency
• Responsibilizing (‘polluter pays’)
Primary Trigger = system imbalance
observed through frequency (aggregated
deviations: imbalance netting!) local
issues
Secondary Trigger = LFCA imbalance (tie
line powerflow versus plan/reference)
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• Frequency is/was a convenient observable (but inertia is
declining, DC is coming, etc.)
• Many local imbalances causing congestions may exist – at
distribution grid level – without a corresponding frequency
deviation ( no FCC activation): imbalance netting
• How to ensure that reserves activations – using distribution grid
connected resources – in response to a global observable
(frequency) does not cause other, additional problems?
• How to make effective use of local resources to solve local
problems locally?
Frequency/Balance Control Current Control Scheme
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Challenge 1: Central detection of the need for reserves
activations
Imbalance netting ‘hides’ the many local problems (only considers
the ‘aggregated’ problem)
Challenge 2: Secure and efficient activations of distribution grid
connected reserves providing resources
What, and how much, can be activated where, so that no new local
voltage or congestion problems are caused by these activations
Improve distribution grid observability/monitoring
Improve TSO/DSO coordination
But:
Communication/aggregation complexity and delays (bottom-up and top-down)
Central trade-off between security, efficiency and computational tractability
Frequency/Balance Control Current Control Scheme
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Balance Restoration Control In Web-of-Cells
Solve local problems locally based on
local observables, acknowledging that:
Cells have tie-line powerflow
setpoints (schedules)
Deviations are observed and
corrective actions are taken using
local (intra-cell) reserves
detailed local information is needed
and available to activate securely
and effectively
System balance is restored as the
aggregated effect of restoring all cell
balances
No imbalance netting : security
cost
add Balance Steering Control
Responsibilizing, ‘the polluter pays’
But local collaboration possible
Divide-and-conquer (smaller cell large
LFCA) : secure and efficient in computational
tractable time
Avoid communication/aggregation complexity
and delays during real-time control
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• In each cell :
− Balance Restoration Controller (BRC): monitor and restore cell tie-
line powerflow profiles (net import/export) to centrally cleared
secure values (representing system balance)
Leveraging many fast acting resources (flex loads and storage instead
of synchronous generators): very high ramping rates
− Cell imbalances = deviations from planned import/export profile
caused by:
Intra-cell incidents or forecast errors
Intra-cell reserves activations for FCC or PVC
PVC: unavoidable
FCC: avoid, or smart/adaptive (based on cell state), or only in
selected cells
Deviations in neighbouring cells (physical connections)
allows for local collaborative balance restoration effort based
on powerflows ( based on global observable like frequency)
Balance Restoration Control In Web-of-Cells
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• Still needing FCC? BRC can be primary (and secondary combined)?
− Leverage opportunities of distributed storage and flexible loads
Can act much faster than the inertia bearing generators that were used before
Can restore faster than current FCC can contain?
Very high ramping rates + ICT : fast enough?
No longer need for separate primary and secondary control
• Or Adaptive FCC
− Avoid frequency deviation triggered activations in
Cells that are ‘in balance’
Cells that are not causing the deviation: responsibilisation
• Local collaboration full responsibilisation secure
activation (not causing new/additional problems like voltage
problems or congestions)
− Introduce locality and proportionality by adding smarter controller
paradigms
Balance Restoration Control in Web-of-Cells
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• BRC loses the benefit of imbalance netting: excess amount of
reserves activations
− Balance Steering Control (BSC) introduces distributed local
(neighbour to neighbour) imbalance netting where neighbours
agree on a modified but still secure setpoint
• Inertia Steering Control/ Inertia
Response Power Control (IRPC)
provides a ‘stable’ amount of
(virtual) inertia irrespective of actual energy mix
Balance Steering Control in Web-of-Cells
BRC possible ramping rate : fast acting resources without inertia (but with
communication and calculation delay)
Needed ramping rate to contain freq deviations (can be influenced by IRPC)
Needed amount of activations if no imbalance netting
(BRC without BSC)
Theoretical needed amount of activations if system-wide imbalance netting
Needed amount of activations if local imbalance netting (BRC with BSC)
DP, D€
DP, D€
Time
Power
Fast BRC with corrective BSC(undoing activations)
Fast BRC without BSC
Slow BRC with proactive BSC(preventing activations)
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• A cell is by design not a microgrid
• In ELECTRA, microgrids are defined as being able to operate in
grid-connected as well as “island”-mode
• Being able to operate in island mode is not a requirement of a
cell.
• …but of course microgrids can easily be a cell once grid-
connected, independent from the size
• However, cells will more and more have attributes of
microgrids.
• This will lead to future integrated grids that are a combination of
Cells that to a great extent, can operate in “island-mode” as well
meeting the needs of the identified essential loads with available
cell resources
WoC vs. Microgrids
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• ELECTRA Decentralized Web-of-Cells concept
− Load Frequency Control Areas smaller cells that are responsible
both detecting the need for reserves activations as well as for the
reserves activation itself
− Local control and collaborations between cells based on local
observables (tieline powerflows) instead of global collaborative
control based on global observable (frequency)
− delegate responsibility for local balance/frequency and voltage
control to local cell operators
Solve local problems locally : less complexity, less communication, more
efficiency (less losses), more secure (less reverse power flows)
Divide-and-conquer : more optimal and more secure within
computational tractability limits
Summary Web-of-Cells Concept
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BALANCE CONTROL
CURRENT GRID FUTURE 2035+ GRID
- Inertia steering control
Frequency containment control (FCC) Adaptive Frequency containment
control (FCC)
Frequency restoration control (aFRC) Balance restoration control (BRC)
Frequency replacement control (mFRC) Balance steering control (BSC)
Summary Web-of-Cells Control Scheme
VOLTAGE CONTROL
CURRENT GRID FUTURE 2035+ GRID
Primary voltage control (PVC) Primary voltage control (PVC)
Secondary voltage control (SVC) Post-primary voltage control (PPVC)
Tertiary voltage control (TVC)
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Lab-scale Validation
• Experimentally implement Web of Cell (WoC) based distributed
real-time control in a number of respected European laboratories
• Demonstrate the effectiveness of distributed controls in relation to a
number of grid scenarios
• Prove the role of the Smart Grid Architecture Model (SGAM) in the
setting of experimental plans and cooperation of multiple partners
• Investigate the local coordination of numbers of devices when
subject to uncertainty in system operation while maximizing the
effective utilization of flexibility
• Compare performance demonstrated across multiple laboratories
• Understand on the basis of experiments the implications of controller
conflict(s) and the relative merits of different controls
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Methodology
• Methodological approach
• Involved partners and laboratories
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Discussion Point: How to validate with impact?
1. What are the major challenges for the validation of distributed
control approaches (like the WoC real-time control approach) in the
domain of smart grids?
2. What is the main advantage of a laboratory experiment (hardware,
software, Hardware-in-the- Loop (HIL)) over a pure software
simulation?
3. What is the value in experimental teams using SGAM?
4. What key features should be included in scenarios that stimulate
genuine interest?
5. What aspects of smart grid systems evaluation are more important
to represent in hardware rather than emulated in software models?
6. How do you assess if a Technology Readiness Level (e.g. TRL6:
validated in operational environment) has actually been achieved?
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CONTACT
INFORMATION
Helfried Brunner [email protected]
Chris Caerts [email protected]
ELECTRA IRP website link: www.ElectraIRP.eu