joint electra/sirfn workshop - integrated...

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.

2 ELECTRA/SIRFN WS onTesting and Research Infrastructure for Future Power Grids 24-Sep-2016, Niagara, Canada

• 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

• Generation will shift from classical dispatchable units to

intermittent renewables

• Generation will shift from few large units to many smaller

• It will shift from central transmission system connected

generation to decentralized distribution system

connected generation

• Electricity consumption will increase significantly

Trends and Assumptions

• 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

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

• 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

• 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

• 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)

• 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

• Objective : System balance restoration (load = generation)

− frequency is just an observable …

Frequency/Balance Control Current Control Scheme

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)

• 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?

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

Communication/aggregation complexity and delays (bottom-up and top-down)

Central trade-off between security, efficiency and computational tractability

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

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

• 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

• 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

• 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€

Fast BRC with corrective BSC(undoing activations)

Fast BRC without BSC

Slow BRC with proactive BSC(preventing activations)

• 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

• …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

• 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

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)

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

Methodology

• Methodological approach

• Involved partners and laboratories

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?

CONTACT

INFORMATION

Helfried Brunner Helfried.brunner@ait.ac.at

Chris Caerts chris.caerts@vito.be

ELECTRA IRP website link: www.ElectraIRP.eu

joint electra/sirfn workshop - integrated...

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