Security and resilience in low carbon, low inertia ... - CIGRE© 2017 P. Mancarella - The University of Melbourne Cigre Workshop, Santiago de Chile, 27 March 2017 1 Security and resilience

© 2017 P. Mancarella - The University of Melbourne Cigre Workshop, Santiago de Chile, 27 March 2017 1

Security and resilience in low carbon, low inertia power systems:

challenges, opportunities, and experience from the South Australia 'Black System'

event of September 2016

GESTIÓN DE RIESGOS EN LA PLANIFICACIÓN Y OPERACIÓN DEL SISTEMA ELÉCTRICO

Santiago de Chile, 27-03-2017

Prof Pierluigi MancarellaChair of Electrical Power Systems

The University of Melbourne


Presentation outline

Context for a changing landscape Renewables and techno-economic implications A textbook example Analogies with Chile Concluding remarks


Context

Renewable energy sources (RES) to address the Energy Trilemma (affordability, security, sustainability)

Variability and unpredictability of RES output pose operational challenges

These are compounded by the lack of synchronous coupling to the grid frequency, due to power electronics interface, for most RES technologies – Decrease of “inertia” in the system

There is a need for rethinking classical concepts of reliability– Adequacy, security

Resilience is a new key aspect to consider


Reliability and system operation

Generation & Transmission

Planning


Planning

Long-term Generation Scheduling


Time-ahead Generation Scheduling


System BalancingSystem

Balancing

Actual delivery: physical generation

& consumption

One day to one hour before

delivery

Months to days before

delivery

Years before delivery

Balancing supply and demand at all times

to guarantee system reliability

Primary and secondary FR and tertiary reserves

Regulation/load following

Balancing markets

Economic dispatch and unit commitment

Operation and Security


Reliability and planning


Planning


Planning






Balancing


& consumption


delivery


delivery




Investment for system

adequacy

Fuel contracts

Maintenance planning

Planning


A changing landscape


Planning


Planning






Balancing


& consumption


delivery


delivery




Investment for system

adequacy Primary and secondary FR and tertiary reserves

Regulation/load following

Balancing markets

Economic dispatch and UCFuel contracts

Maintenance planning

InertiaInertia

Ramping and

flexibility

Ramping and

flexibilityShort term economic dispatch

Short term economic dispatch

Extreme events

Extreme events


Variability, energy and secure capacity

Source: P. Mancarella et al, Business case for flexible demand, Final report for the DD-FD project

Conventional capacity and energy displacement at various levels of wind penetration, future UK scenarios, 55GW peak


What’s happening to conventional thermal generators?

Lower capacity factors mean higher average costs of production (including fixed costs)

More renewables mean lower average prices and lower operational hours to recover fixed costs

What will happen next?


How do we provide security today?


Is it only an issue of reliability?

Reliability Resilience

High-probability, low-impact Low-probability, high-impact

Static, not-dynamic (either reliable or not)

Adaptive, ongoing, long term, time-dependent

Concerned with customer interruption time

Concerned with customer interruption time and the infrastructure recovery time

Reliability vs Resilience

M. Panteli and P. Mancarella, The Grid: Stronger, Bigger, Smarter? Presenting a conceptual framework of power system resilience, IEEE Power and Energy Magazine, May/June 2015, Invited Paper.


The Australian NEM

World’s longest interconnected power system (5,000 km)


A textbook example: the South Australia

“Black system” Event

Context

- Over the last few years, renewable generation has increased rapidly in South Australia, which now has over 1,400 MW of wind capacity and 600 MW of solar PV capacity

- As a region, South Australia has a peak demand of around 3,300 MW, and therefore has one the highest proportions of renewable generation in the world

- SA is interconnected to the rest of the NEM by several transmission lines with a combined capacity of around 800 MW

- South Australian demand has not grown recently, and so there has been a reduction in the energy provided by conventional generation as well as a withdrawal of conventional generation capacity




DC link

Heywood

Interconnector




System Risks

- Increasing wind generation may lead to economic displacement of thermal generation

- This would make it more difficult to manage power system frequency after a contingency event, given that today security (via Frequency Control Ancillary Services - FCAS) is primarily provided by conventional generators


Ancillary services example: Outage of large generating unit

Primary response

Secondary response

OCGT

Can this be a wind park dropping out due to

voltage stability issues?

MW

49.20

49.30

49.40

49.50

49.60

49.70

49.80

49.90

50.00

50.1012

:24:

00

12:2

4:30

12:2

5:00

12:2

5:30

12:2

6:00

12:2

6:30

12:2

7:00

12:2

7:30

12:2

8:00

12:2

8:30

12:2

9:00

12:2

9:30




System Risks


- This would make it more difficult to manage power system frequency after a contingency event, given that today security (via FCAS) is primarily provided by conventional generators

- The analysis also needs to include considerations on the so-called Inertial response and Rate of Change of Frequency (RoCoF)


Ancillary services example: Outage of large generating unit

Primary response

Secondary response

OCGTMW Inertial response

49.20

49.30

49.40

49.50

49.60

49.70

49.80

49.90

50.00

50.1012

:24:

00

12:2

4:30

12:2

5:00

12:2

5:30

12:2

6:00

12:2

6:30

12:2

7:00

12:2

7:30

12:2

8:00

12:2

8:30

12:2

9:00

12:2

9:30


Frequency Response and Reserves

RoCoF

~ 1/H




System Risks


- This would make it more difficult to manage power system frequency after a contingency event, given that today security (via Frequency Control Ancillary Services - FCAS) is primarily provided by conventional generators

- This also needs to include considerations on inertial response and Rate of Change of Frequency (RoCoF)

- Too high RoCoF could cause issues in Automatic Under-Frequency Load Shedding (UFLS) to respond quickly enough


A textbook example: the South

Australia “Black system” Event

The “Black System” event

- A power system failure, or “black system event”, occurred in South Australia on 28 September 2016, resulting in the loss of power to all customers in SA

- The simultaneous loss of multiple generating units or transmission lines, including the Heywood interconnector, was considered a non-credible contingency


A textbook example: the South Australia “Black

system” Event


- Severe weather had been forecast, including for lightning strikes

- AEMO considered whether to reclassify these contingencies as credible, but based on forecasts at the time and the known vulnerabilities of the area, decided not to do so

Source: AEMO

import

thermal

wind



system” Event


- During the event, severe weather caused the loss of three major power lines north of Adelaide in a 40 second period

- This loss caused multiple transmission faults and relevant voltage transients to occur

- Both thermal and renewable generators had fault ride-through capability of varying kinds

- However, the control systems of some wind farms were configured to disconnect or reduce output when multiple faults occurred over a certain period



system” Event


- 9 wind farms reduced their output by a total of -445 MW in approximately 2 seconds

- Power flow on the Heywood interconnector partially compensated for this loss by increasing to 890 MW (emergency capacity of 750) in less than 1 second

- The resulting power flow caused it to disconnect to protect itself by activation of loss of synchronism (high current and low voltage driven) relays

- It appears that both transient and voltage instability phenomena took place, with consequent loss of steps of synchronous generators and voltage collapse




Source: AEMO





- The frequency in the SA power system dropped with a RoCoF of over 6 Hz/s, too rapidly for Automated UFLS Schemes to operate, and the power system frequency dropped below 47 Hz in 0.2s

- All remaining generation and the Murraylink interconnector therefore tripped, causing the black system event




Source: AEMO




Immediate reactions

- For a few weeks, AEMO was directed to operate the power systems to restrict RoCoF to less than 3 Hz/second in the event that the Heywood interconnector was to fail

- The simultaneous tripping of 10 wind farms was reclassified as a credible contingency

- Wind farms are being asked to reconfigure their control systems

- Investigations are ongoing

- Lots of research is needed


Analogies Australia-Chile

- Long and “radial” system

- To become even longer after the interconnection

- Huge RES potential

- Potentially significant amount of RES output at the edge (e.g., Atacama)

- Balancing provided through interconnection (hydro)

- Relatively weak interconnectors with other countries


What next for R&D

- New operational measures

- Minimum synchronous generation levels

- New techniques to assess contingency credibility

- Operational planning for resilience

- Development of new power systems tools

- Mixed static-dynamic constraints

- Advanced RES modelling

- Frequency-constrained optimal power flow

- New technologies to support “frequency adequacy”

- Synthetic inertia and frequency response from RES

- Fast frequency response

- Assessing the role of interconnectors to provide security


UK example – National Grid “Gone

Green” scenario

Frequency after 1.8GW generator loss event:Batteries providing Fast Frequency Response


Enhancing Grid Resilience- Hardening/reinforcement measures (“stronger” and “bigger”)

- Smart/operational measures (“smarter”)

Cost Vs Effectiveness – Conceptual comparison

M. Panteli and P. Mancarella, The Grid: Stronger, Bigger, Smarter? Presenting a conceptual framework of power system resilience, IEEE Power and Energy Magazine, May/June 2015, Invited Paper.


Concluding remarks

The energy trilemma brings significant techno-economic and reliability challenges– The South Australia black event has been a textbook

case

There is a need for new tools to assess system operation and then investment in the light of new “frequency adequacy” requirements

Substantial research to be done on the role of new operational models, technologies and interconnectors in providing frequency control ancillary services


Thank you!

Any Questions?

[email protected]

mailto:[email protected]


Acknowledgements

The organizing committee for the kind invitation The UK EPSRC for the support to carry out the UK-Chile

project on “Disaster Management”


Security and resilience in low carbon, low inertia power systems:

challenges, opportunities, and experience from the South Australia 'Black System'

event of September 2016

GESTIÓN DE RIESGOS EN LA PLANIFICACIÓN Y OPERACIÓN DEL SISTEMA ELÉCTRICO

Santiago de Chile, 27-03-2017

Prof Pierluigi MancarellaChair of Electrical Power Systems

The University of Melbourne

Slide 1Presentation outlineContextReliability and system operationReliability and planningA changing landscapeVariability, energy and secure capacityWhat’s happening to conventional thermal generators?Slide 9Slide 10How do we provide security today?Slide 12Slide 13Slide 14Slide 15Slide 16Ancillary services example: Outage of large generating unitSlide 18Ancillary services example: Outage of large generating unitFrequency Response and ReservesSlide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Concluding remarksSlide 35AcknowledgementsSlide 37

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Security and resilience in low carbon, low inertia ... - CIGRE© 2017 P. Mancarella - The University of Melbourne Cigre Workshop, Santiago de Chile, 27 March 2017 1 Security and resilience