Power System Challenges of Increasing Renewables

100% Converter-Based Grids

Damian Flynn

Facilitation of Renewables Studies

Fundamental issues

Loss of

largest infeed

Issues that can be mitigated

Voltage Stability Transient Stability

Network Loading

Fundamental issues that need further analysis

Non-issues according to modelling

Voltage Control

Fault LevelsSmall Signal

Stability

Temporary loss of

wind power due

to network faults

Frequency Stability

Short term

frequency

variations

Power balance

fluctuations

and frequency

regulation

Frequency Stability

Ireland and Northern Ireland

Facilitation of Renewables StudiesIreland and Northern Ireland

Annual System Inertia

0 -4 10-14 20-24 30-34 40-44

5-9 15-19 25-29 35-39 MWs

20

15

2

01

4

20

13

2

01

2

Ireland and Northern Ireland

Operational Capability Outlook

Power System Transition

Before System Split …

… After System Split

4 November 2006 – Norwegian Pearl

4 November 2006 – System Split

4 November 2006 – Area Frequency Sy

stem

Fre

qu

en

cy (

Hz)

4 November 2006 – System Split

100% Converter-Based Grids

• No conventional synchronous generation

• What is meant by system frequency?

• Achieving load balancing with ‘local’ controls?

• Operational rules in a ‘100%’ state?

• Requirement for (new) system services?

• …

• Achievable without ‘smart grid’ communications?

Load Balancing (Frequency Control)

Synchronous generator

(Fixed speed) wind turbine generator

50/60 Hz

+ Solar PV+ (Variable speed) wind+ HVDC interconnection+ Tidal stream+ Ocean wave + …

Grid-Forming Control Strategy

Existing inverters are grid-following

SG

SG

50 Hz

What to follow?

50 Hz

Some / many future inverters need to be

grid-forming

Modelling Environment?

Existence of implicit synchronous machine based assumptions?

Future Transmission Network

Grid-Forming Converter Model

Modelling Complexity?

Reduced order converter modelsFull order converter models

Co

nve

rter

cu

rren

t (p

u)

Time (s)

Control Hierarchy?

0

100

200

300

400

500

1 7 13 19

Win

d P

ow

er

(MW

)

Time (Hours)

Cork Antrim Donegal

0

100

200

300

400

500

1 7 13 19

Sola

r P

ow

er

(MW

)

Time (Hours)

Valentia Belfast Kilkenny

0 6 12 18 0

0 6 12 18 0

Time Series Modelling

Future Plans …

• Power system stability assessment• New technical challenges?

• Robustness to system splits + Blackstart capability

• …

• Transitions between ‘100%’ state or ‘<100%’ state

• Definition of (new & existing) system services?

• Migration path from current to new ‘controls’?

• Equipment requirements and grid code updates?

• …• Telecommunication infrastructure?

Future Plans …

Hardware in the Loop Simulation

Power System Challenges of Increasing Renewables

100% Converter-Based Grids

Damian Flynn