Increasing PV Hosting Capacity in Distribution Networks ...

© 2018 A.T. Procopiou - The University of Melbourne MIE Symposium, December 2018 1

Increasing PV Hosting Capacity in Distribution Networks: Challenges and Opportunities

The University of Melbourne

Melbourne Institute of Energy Symposium

12th December 2018

Dr Andreas T. Procopiou

Research Fellow in Smart Grids

[email protected]

www.andreasprocopiou.com

mailto:[email protected]

http://www.andreasprocopiou.com/


▪ Solar PV in Australia

– Status, installations and cumulative capacity

▪ Challenges in PV-rich Distribution Networks

– Traditional and non-traditional mitigation approaches

▪ Understanding Solar PV impacts

▪ Smart PV Inverters

– Embedded Control Functions

– Increasing PV Hosting Capacity

▪ Residential Battery Energy Storage Systems

– Opportunity for advanced controllers (to manage technical issues)

▪ Conclusions

Outline


Solar PV in Australia

5.00

6.00

7.00

8.00

9.00

10.00

Tota

l In

sta

lled

Cap

acit

y (

GW

)

0

1

2

3

4

5

6

7

8

9

0

2

4

6

8

10

12

14

16

18

20

Thousands

Total Monthly Installations

Average Installed Capacity

Nu

mb

er o

f In

sta

llati

on

s

Cap

acit

y (

kW

p)

12

3%

2 million Installations

2016 0.8GW

62

%

2017 1.3GW

18GW by 2020

Solar PV Status, Australia: Australian PV Institute, 2018. [Online]. Available: https://goo.gl/n8CJfF. Accessed on November 2018

Installations Cumulative Installed Capacity 2018 2.9GW


Challenges in PV-rich Distribution Networks

Bulk Generation

Transmission

Bulk supply point

Distribution

MV/LV

Max

MinDistance

VoltagePV Systems

NotGenerating


Challenges in PV-rich Distribution Networks

Bulk Generation

Transmission

Bulk supply point

Distribution

MV/LV

Max

Min

Voltage rise

Distance

Voltage

Technical issues brought by high penetrations of solar PVsignificantly reduces hosting capacity of networks

Traditional Solutions

Network Reinforcement

PV Systems Not

Generating

PV Systems Generating

Congestion


Challenges in PV-rich Distribution NetworksSolutions

Bulk Generation

Transmission

Bulk supply point

MV/LV

Max

MinDistance

VoltageTraditional Solutions

Network Reinforcement

Bigger Transformers Larger Cables


Non-Traditional Solutions

Storage and solar PV (reduce household exports)

Challenges in PV-rich Distribution NetworksSolutions

Bulk Generation

Transmission

Bulk supply point

Distribution

Max

MinDistance

MV/LVGeneration Curtailment

Reactive Power Absorption

Non-Traditional Solutions

Smart PV inverter capabilities (reduce household exports)

Reinforcement Alternative

Leveraging existing assets to manage technical issues and increase hosting capacity


Understanding Solar PV Impacts

▪ Real Victorian 22kV HV feeder

– ‘Strong’ semi-urban

– 30km of conductors

– 79 distribution transformers

– Realistically Modelled LV Networks

• Australian Design Principles

• 175 LV feeders

• 4612 residential customers

▪ Stochastic Analyses - Monte Carlo

– Summer (December – February)

– Varying locations and sizes (using regional PV stats)

– Smart meter demand and PV generation

– PV penetration increments of 10% (0-100%)

• % of customers with PV systems

“Solar PV Penetration andHV-LV Network Impacts” Project

Completed project

1 A. Navarro, L.F. Ochoa, Probabilistic impact assessment of low carbon technologies in LV distribution systems, IEEE Trans. on Power Systems, May 2016 (10.1109/TPWRS.2015.2448663)

1


Understanding Solar PV ImpactsStochastic Impact Analyses

LV Voltage Issues

“Solar PV Penetration andHV-LV Network Impacts” Project

Hosting Capacity: 20% PV Penetration* Off-load taps at nominal position (3) and Volt-Watt function as per AS/NSZ 4777.2:2015

Completed project

HV Conductors Congestion

Default Volt-Watt settings (AS/NSZ 4777.2:2015) not adequate to manage issues


Smart PV InvertersEmbedded Controllability

▪ Embedded with power control functions

– Volt-Watt

– Volt-var

– Fixed PF

– Watt-PF

– Power Limit

▪ Embedded with communication interfaces

Sourc

e:

ww

w.s

ola

redge.c

om

Sourc

e:

ww

w.s

ma

-austr

alia

.com

.au

Sourc

e:

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w.a

bb.c

om


3. Volt-var Control Function

2. Volt-Watt Control Function1. Active Power Limit Function

4. Watt-PF Control Function

(a) Watt Priority

(b) Var Priority

(c) 10% Oversized with Watt Priority

(a) Watt Priority

(b) Var Priority


Watt Priority

Var Priority

Inverter Power Priority

Limited Q

Smart PV InvertersEmbedded Control Functions


Smart PV InvertersControl Function Examples

▪ Example settings used for demonstration purposes:

-100%

-50%

0%

50%

100%

0.9 0.94 0.98 1.02 1.06 1.1

% o

f avail

ab

le V

ars

Voltage (p.u.)

0%

25%

50%

75%

100%

1.05 1.06 1.07 1.08 1.09 1.1 1.11 1.12

Max W

att

Ou

tpu

t (%

of

max o

utp

ut)

Voltage (p.u.)

Volt-Watt Volt-var

A. Procopiou, Active Management of PV-Rich Low Voltage Networks, PhD Thesis, The Univ. of Manchester, 2017 (https://www.escholar.manchester.ac.uk/item/?pid=uk-ac-man-scw:310939)


Smart PV InvertersVoltage Issues

▪ 60% PV Penetration on the Australian HV-LV Network

BAU

34% 0%

Volt-Watt Volt-var

34%

• Volt-Watt control effective at the expense of energy curtailment • Volt-var control ineffective due to limited Q when needed

12% curtailment


Smart PV InvertersVoltage Issues

▪ 60% PV Penetration on the Australian HV-LV Network

BAU

34% 0%

Volt-Watt Volt-var

34%

• Volt-Watt control effective at the expense of energy curtailment • Volt-var control ineffective due to limited Q when needed

12% curtailment

Volt-var(oversized or Var priority)

0%


▪ 60% Penetration on the Australian HV-LV Network

BAU

5 Txs overloaded

Volt-Watt Volt-var

0 Txs overloaded

6 Txs overloaded

• Curtailment from Volt-Watt eliminates Tx overloads• Q from Volt-var creates more overloads

Volt-var (oversized)

7 Txs overloaded

HIGHER UTILIZATION

Smart PV InvertersThermal Issues


-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

0.85 0.9 0.95 1 1.05 1.1 1.15

Reactive P

ow

er

(% A

vailable

VARs)

Voltage (p.u.)

California

Hawaii

IEEE-Cat A

IEEE-Cat B

AU/NZ

Italy/Austria

0%

20%

40%

60%

80%

100%

120%

1 1.05 1.1 1.15

Active P

ow

er

(% M

ax P

ow

er)

Voltage (p.u.)

IEEE/Hawaii

AU/NZ

Austria

0.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

0% 20% 40% 60% 80% 100%

Pow

er

Facto

r

Active Power (% Max Power)

AU/NZ

Italy/Austria/Germany

Volt-var

Volt-Watt

Watt-PF

(a) Watt Priority

(b) Var Priority


Smart PV InvertersControl Function Settings and Options


-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

0.85 0.9 0.95 1 1.05 1.1 1.15

Reactive P

ow

er

(% A

vailable

VARs)

Voltage (p.u.)

California

Hawaii

IEEE-Cat A

IEEE-Cat B

AU/NZ

Italy/Austria

0%

20%

40%

60%

80%

100%

120%

1 1.05 1.1 1.15

Active P

ow

er

(% M

ax P

ow

er)

Voltage (p.u.)

IEEE/Hawaii

AU/NZ

Austria

0.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

0% 20% 40% 60% 80% 100%

Pow

er

Facto

r

Active Power (% Max Power)

AU/NZ

Italy/Austria/Germany

Volt-var

Volt-Watt

Watt-PF

(a) Watt Priority

(b) Var Priority


Smart PV InvertersControl Function Settings and Options

Which is more adequate to mitigate issues?

What settings offer more benefits?

Extend of additional Hosting Capacity?

Significant number of solution options – Complex!


Primary Substation

Distribution Substation

Increasing PV Hosting CapacityHosting Capacity and Impact Solutions Assessment Tool

Selection of Network

Specification of new PV (location, inverter)

Hosting Capacity Limit Assessment

Solutions Assessment

Next Level Hosting Capacity Limitation

Analysis Summary

Location of new PV System

Technical Issues

Analysis Summary – Used by Distribution Network Planners

“Solution Methods for Increasing PV Hosting Capacity” Project

On going project

Real 22kV Feeder (200+ Dist. Tx, 500+ Customers)


Residential Battery Energy Storage SystemsStatus in Australia

Sou

rce:

Cle

an E

ner

gy A

ust

ralia

Rep

ort

20

18

0

5

10

15

20

25

2015 2016 2017

Num

ber

of In

sta

llations

Thousands

three-fold increase

from 2016

RESIDENTIAL ENERGY STORAGE SYSTEM INSTALLATIONS

Source: Clean Energy Australia Report 2018

Increasing interest of customers in Battery Energy Storage (BES)

Store excess of PV generation and use it later

Reduce grid imports; hence electricity bills


▪ Off-the-shelf (OTS) BES operate for the sole benefit of the customer

– Do not provide benefits to the network1

Residential Battery Energy Storage SystemsOff-the-shelf Operation and the Opportunity

▪ BES systems have different control capabilities

– Opportunity to provide benefits to both network and customers

– Reduce reverse power flows, hence, network issues

– Alternative to costly network reinforcements

– Allow customers reduce electricity bills

Household with 5kWp PV system, and 5kW/13.5kWh BES system

1K. Petrou, L.F. Ochoa, A.T. Procopiou, J. Theunissen, J. Bridge, T. Langstaff, K. Lintern,"Limitations of residential storage in PV-rich distribution networks: An Australian casestudy" 2018 IEEE Power & Energy Society General Meeting

OTS Battery

Controller


▪ The Developed Battery Controller:

– Adapts charging power to the PV generation and Demand

• Reduces reverse power flow during peak generation periods

– Ensures available capacity by discharging overnight

– Always supports the demand, throughout the day

– Adapts to sudden changes in demand and generation

▪ No Communication Infrastructure Required

▪ Uses Local Measurements and Known Data

– Local Measurements: PV generation, Demand, SOC

– Known data: Clear-sky irradiance

1A.T. Procopiou, K. Petrou, and L.F. Ochoa, "A controller for photovoltaic generation and energy storage system," Australia Patent2018904310, 2018. Available: https://goo.gl/VYsFMJ.

Residential Battery Energy Storage SystemsResidential Storage Controller for the Benefit of Customers and Networks1

Reinforcement Alternative


PV Only Off-the-Shelf (OTS)With Proposed

Battery Controller

▪ Voltages

10% Non-Compliant No Voltage Issues18% Non-Compliant

Residential Battery Energy Storage SystemsNetwork Benefits


▪ Asset Utilization

PV Only Off-the-Shelf (OTS)

No CongestionsLines and TXs CongestedLines and TXs Congested

Residential Battery Energy Storage SystemsNetwork Benefits

With Proposed Battery Controller

With Proposed Battery

Controller


▪ Customer Grid Dependency - Year Analysis

Grid Dependence Index

% of demand imported from the grid

100% = Fully dependant to the grid

0% = Energy Self-Sufficient

Residential Battery Energy Storage SystemsCustomer Benefits

With Proposed Battery Controller


Conclusions 1/2

▪ DNSPs face challenges evaluating the growing penetrations of PV systems

– Locational and behavioral uncertainties of PV systems

– Simplified impact analyses are not adequate to cover uncertainties

▪ Advanced computational simulation models and techniques are required

– Detailed time-series analyses (three-phase, MV-LV, daily/seasonal demand/generation)

– Stochastic assessment (catering for uncertainties)

▪ Increasing PV hosting capacity: Leveraging existing assets (cost effective)

– Smart PV Inverters offer a wide range of solution options

• Volt-Watt is effective but in expense of curtailment

• Volt-var might be effective (if capability exists) but exacerbates asset utilization

• Complexity in identifying the most adequate combination of control and settings

• Advanced solution assessment tools required


Conclusions 2/2

▪ Increasing PV hosting capacity: Leveraging existing assets (cost effective)

– Residential BES Systems

• OTS control strategies (customer benefit oriented) do not increase PV hosting capacity

• Opportunity for new storage control strategies providing benefits to both:

– Network (management of technical issues, increasing HC)

– Customers (reduced grid imports, hence electricity bills)

▪ Trade-off between technical performance, customer impacts, practicality, and cost should always be taken into consideration


Thank you!

Acknowledgement

• Mr Kyriacos PetrouPhD Student

• Prof Luis F. OchoaProfessor in Power Systems


Increasing PV Hosting Capacity in Distribution Networks: Challenges and Opportunities

The University of Melbourne

Melbourne Institute of Energy Symposium

12th December 2018

Dr Andreas T. Procopiou

Research Fellow in Smart Grids

[email protected]

www.andreasprocopiou.com

mailto:[email protected]

http://www.andreasprocopiou.com/

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