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© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 1
The Australian Approach to
Solar PV and Distribution Networks
Universidad Adolfo Ibáñez (UAI) | Santiago, Chile
3rd June 2024
Prof Luis(Nando) Ochoa
Professor of Smart Grids and Power Systems
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 2
Outline
1. Context
2. Making the most of PV Inverters
3. Making the most of Existing Infrastructure
4. Next Step: Flexible Limits
5. Key Remarks
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 3
1Context
Some Stats 2023
Peak (net): 32.5 GW (NEM)1
Australia PV: 32.1+ GW, 3.5+ million installations2
1 in ~3 houses with PV (2+ out of 10 million)
Avg. size in 2023: 9kW3
Residential Batteries: ~180k installations4
1 Australian Energy Regulator
2 Australian PV Institute
3 Australian Energy Council
4 SunWiz
NEM: National Electricity Market (Eastern half Australia)
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 5
1 Australian Context
Solar PV & Low Voltage (LV) Networks
V
Max
Min
I
I
V
Off-LTC
LV Feeder (3): 400V L-L
Homes (1): 230V L-N
The sun shines to all ☺
PV generation happens simultaneously and when many people
are not at home → Voltage and thermal issues
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 6
1 Australian Context
Solar PV & High Voltage (HV) Networks
Primary Sub
OLTC
Off-LTC
HV Feeder (3): 22kV L-L
Widespread PV adoption → Widespread problems
7
8
2 Making the Most of PV Inverters
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 9
2 Making the Most of PV Inverters
Local Solutions
➢PV Inverter Functions
Combines Volt-Watt and Volt-var (Q priority)
More effective than Volt-Watt alone
But many installations have the old Volt-Watt or
no function enabled
➢Export Limits at the Meter
Commonly 5kW per phase1
People use 5kVA inverters (even if panels are
larger) or inverters that can do export limits
Avg. installation in 2023 is ~9kW of panels
Can be less (2, 1, 0kW) depending on location
Growing number of customers affected
1 3.5kW per phase in SWER networks (rural areas)
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 10
2 Making the Most of PV Inverters
Volt-Watt and Volt-var
▪Latest Australian standard: AS/NZS 4777.2:20201
1
Volt-Watt Volt-var (Q priority)
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 11
2 Making the Most of PV Inverters
Volt-var and Reactive Power Priority
▪Example with inverter with 0.9 PF lead/lag capability
Active Power (P)
Priority
Reactive Power (Q)
Priority
Q priority → Q is used when needed → Better V management
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 12
2 Making the Most of PV Inverters
Example: Victorian Urban Network
Non-Compliant Cust. Tx Utilisation
HV Utilisation
Non-Compliant Cust. Tx Utilisation
HV Utilisation
Volt-Watt Volt-Watt & Volt-var
Urban VIC
CRE21 (22kV)
Effective use of PV inverters
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 13
2 Making the Most of PV Inverters
Example: Victorian Urban Network
Volt-Watt Volt-Watt & Volt-var
Minimal curtailment → Added value to customers
this standard is relatively new and many non-compliant inverters
14
3 Making the most
of Existing Infrastructure
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 15
3 Making the most of Existing Infrastructure
Off-LTCs and OLTCs
➢Off-Load Tap Changers
•This is the obvious thing to do for most distribution
companies
•Taps: -5%, -2.5%, 0%, 2.5% and 5%
•Very effective given that voltages were always pushed to
higher values
•Challenge: Voltage drops due to electrification (EVs, heating,
cooking)
➢Active use of On-Load Tap Changers (Primary Sub)
•Combined with Smart Meter Data (e.g., Victoria)
•AKA Dynamic Voltage Management System (United Energy)
•Very effective but measurements and associated IT are
needed
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 16
3 Making the most of Existing Infrastructure
Example: Off-Load Tap Changers (CRE21)
Business-as-Usual: 50% PV Penetration
Voltage Transformer HV Lines PV Systems
Reduced Taps: 50% PV Penetration
Voltage Transformer HV Lines PV Systems
2 taps
availability
Off-LTCs → Simple and effective
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 17
3 Making the most of Existing Infrastructure
Example: Dynamic Voltage Target (CRE21)
Customer
Voltages
No voltage issues until very high PV penetration
18
Next Step: Flexible Export Limits
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 19
4 Next Step: Flexible Limits
Moving away from fixed limits
▪As solar PV uptake continues, fixed export limits are getting smaller
Why is this bad? Discourages PV adoption, discourages services through aggregators,
inefficient use of the network and PV generation most of the time.
▪In 2023, the regulator gave the OK for flexible export limits1.
Distribution companies have started offering it to residential customers.
Flexible Limits
(aka Operating Envelopes)
Import
Export
Fixed Limits
Import
Export
Opt-In
1
https://www.aer.gov.au/system/files/Flexible%20Export%20limits%20Final%20Response%20-%20July%202023_1.pdf This is a world-first ☺
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 20
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Exports (kW)
5-min Interval
OE / Flexible Exports
1.5kW Fixed Export Limit
4 Next Step: Flexible Limits
The Benefit
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Exports (kW)
5-min Interval
OE / Flexible Exports
1.5kW Fixed Export Limit
8kVA PV System
OE → 120% More
Energy Exported
3.5kVA PV System
OE → 20% More
Energy Exported
✓OEs can unlock much more PV generation with the same poles and wires
✓System operator and society benefit from more/new resources
→ Lower emissions, cheaper electricity, new services, operational opportunities, etc.
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 21
4 Next Step: Flexible Limits
How would this work?
V
I
Calculation of DER
or Meter-Level
Limits
Broadcast to
DER or
Aggregators
→
✓ DER uses available capacity
✓ Bottom-Up Services
✓ Network Integrity
→
DER acts or
aggregator decides
how to act
→
kW
t
kW
Exp
Imp
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 22
4 Next Step: Flexible Limits
Calculating the limits
▪Time-varying export/import limits at the
connection point of flexible customers
Flexible Customer: Opted for flexible limits
Fixed Customer: Fixed limits (can have DER)
▪Calculated for specific times
➢In real time (e.g., next 5 min) or in advance
(e.g., next 24 hours, every 5 min)
➢Network utilisation (Volts and Amps) varies during
the day. Limits need to capture that.
Data availability (measurements, network models)
drives how they can be calculated.
→ less accuracy
A19
A6
A18
A28
A21
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A13
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A3
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A23
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A2
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A14
A12
A11
A1
Example of Operating Envelopes (OEs) from Project EDGE
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 23
4 Next Step: Flexible Limits
(Calculation) Challenges 1/4
▪The ability of the network to handle DER or bottom-up services changes based on
a. Demand and generation (customers not managed by aggregators)
b. Location (customers managed by aggregators)
Local Demand → Feasible Exports
1 We need observability of passive customers * Service cable/fuse
constraint not considered
4kW
15kW 4kW 7kW
At noon (max 15kW, 1 only)
DER or
Bottom-Up
Services
At night
4kW
15kW 4kW 23kW*
(max 15kW, 1 only)
Thermal
constraints
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 24
4 Next Step: Flexible Limits
(Calculation) Challenges 2/4
▪The ability of the network to handle DER exports (and imports) changes based on
a. Demand and generation (customers not managed by aggregators)
b. Location (customers managed by aggregators)
Adding Voltage
Constraints
(non-linear)
4kW 4kW 5kW
At noon (max 15kW, 1 only) 1.10pu (253 V)
!
13kW
DER or
Bottom-Up
Services
At noon
7kW 4kW 4kW
(max 15kW, 1 only) 1.10pu (253 V)
!
15kW
Distance to the transformer → Feasible Exports ↓
2 The physics need to be captured 3 Fairness needs to be in mind
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 25
4 Next Step: Flexible Limits
(Calculation) Challenges 3/4
1. To really capture the physics → Production of Electrical Models for LV feeders
Advanced techniques and site visits are needed
Time-consuming, not cheap
2. To really capture the physics → Lots of Data is Needed
Smart meters (residential, C&I)
Additional monitors (dist. transformer)
Granular forecasting
3. Development of novel Algorithms
Need to be implementable, fast and scalable
Requires many practical considerations
Tx
Immense effort is required to bring everything together.
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 26
4 Next Step: Flexible Limits
(Calculation) Challenges 4/4
4. Allocation principles that are fair
•Equal Opportunity: favours fairness (every customer gets the same value or pro rata)
•Maximise Services: favours efficiency (highest aggregated value, but penalises some)
Equal Opportunity Maximise Services1
From 12pm to 2pm
Average potential exports (all): 77kW / 154kWh
Average potential exports (A17): 4.5kW / 9kWh
From 12pm to 2pm
Average potential exports (all): 55kW / 110kWh
Average potential exports (A17): 5.5kW / 11kWh
1 Requires capturing sensitivity of customers to voltages.
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 28
4 Next Step: Flexible Limits
What do they look like? Project EDGE Site A (3
LV)
Export
Import
Export
Import
A robust network that can support much more exports beyond the typical 5kW limit.
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 29
4 Next Step: Flexible Limits
What do they look like? Project EDGE Site E (SWER)
Export
Import
12.7kV Topology
Export
Import
SWER Iso.
Transformer
High PV penetration (~50%) creates significant bottlenecks for exports around noon.
9AM 3PM
Import capacity is split
between the two (2)
active customers from
this transformer.
30
5 Key Remarks
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 31
5 Key Remarks
▪Australia is making the most of PV inverters through standards
Not many countries use combined Volt-Watt and Volt-var (low hanging fruit)
▪When possible, distribution companies are using off- and on-LTCs
Same in many countries around the world → Cost-effective
▪Australia is the first in the world to implement flexible limits for houses
Distribution companies are gearing up to their next regulatory periods
There are multiple challenges to get it right though (data, accuracy, cost, etc.)
Many lessons to be learned from Australian trials and current practices ☺
© 2024 The University of Melbourne | L. Ochoa The Australian Approach to Solar PV and Distribution Networks, June 2024 32
Further Reading
▪
▪Project Advanced Planning of PV-Rich Distribution Networks
▪Project EDGE
▪Project Flexible Export Limits
▪PV Inverter Functions
AS/NZS 4777.2:2020 Grid connection of energy systems via inverters, Part 2: Inverter
requirements
▪PV Interoperability
AS 5385:2023 Smart Energy Profile Application Protocol
Common Smart Inverter Profile
Common Smart Inverter Profile Australia
33
luis.ochoa@unimelb.edu.au
Thanks!
Questions?
Acknowledgement
•Andreas Procopiou (past)
•Will Nacmanson (past)
•Arthur G. Givisiez
•Michael Liu
•Angela Simonovska
•Eshan Karunarathne
•Melbourne Energy Institute