pv-rich communities, storage, and flexibility: the need for...

© 2018 L. Ochoa - The University of Melbourne PV-Rich Communities, Storage, Flexibility, and DSOs, May 2018 1

PV-Rich Communities, Storage, and Flexibility: The Need for DSOs

15th May 2018

SBSE 2018, Niteroi - RJ, Brazil

Prof Luis(Nando) Ochoa

IEEE PES Distinguished Lecturer

Professor of Smart Grids and Power Systems

[email protected]


Outline

Context: Towards Smart & Low Carbon Flexibility

Challenges in PV-Rich Communities

– Impacts and Potential Solutions

– PV, Battery storage, Control strategies

– Australian (VIC) Case Study

Flexibility and the need for DSOs

– Challenges

Conclusions


Smart & Low Carbon

Bulk Generation

Homes, Schools, Shops, Businesses

Renewables have a significant role

Distributed Generation

Medium-scale renewables and storage

Controllable

New Service Markets

$

Coordinated T-D operation

Small-scale low carbon technologiesResponsive demand

Local control

Hierarchical control

Customer energy management

Centralised network managementHigh asset utilisation

High renewable harvesting

OptimisationForecasting

Real-time monitoring

Frequency responseNetwork operation

Storage


But before we get there…


Challenges in PV-Rich LV Networks

PV generation happens during the day, when many people are not at home Problems

V

Max

Min

II

V

Off-LTC


Challenges in PV-Rich HV Networks

Wide-spread PV adoption Challenges to HV networks

How can we address this?

Primary SubOLTC

Off-LTC

V

I


With existing assets

– Better tap settings for LV Off-LTCs and better voltage target for HV OLTCs

– PV inverters: curtailment, Volt-Watt, Volt-var, etc.

With new assets

– Reinforcements (transformer, conductors)

– Voltage regulation with LV OLTCs

– Active control of PV inverters

– Residential storage devices

– Community storage devices

(Some) Potential Solutions

Which are the most cost-effective solutions?


V

I

V

I

LV Networks andPV-Storage Systems

PV impacts could be avoided using batteries to store excess generation for later

Max

Min

Batteries


… but people will buy storage.

Surely, this will sort it out (?)


Storage:Off-The-Shelf Control and Sizing

Day (generation) Store the exports until full

Night (no generation) Supplies the house load until empty

Size of battery Enough to meet the average exports

Average energy production

High exports day

Storage becomes full network issues?


… Does residential storage

help mitigating PV impacts?


Australian Case StudyHV-LV Network

Victorian 22kV HV feeder

– ‘Strong’ semi-urban feeder

– 79 distribution transformers

(Pseudo) LV Networks

– Constructed based on Australian design principles

• Tx / ADMD = # customers

• # feeders (240mm240 cust.)

• Length (max equiv. lengths and # customers per feeder)

175 LV feeders, 4612 customers

~9MW of peak demand

Anonymised data


Off-The-Shelf (OTS) Storage

Designed to reduce grid imports

– Charge to capture all excess generation (negative net demand)

– Discharge to supply load (positive net demand)

PV generation starts

PV generation ends


Probabilistic Approach

Monte Carlo Analysis

– Real smart meter demand and PV generation profiles

• Anonymised data

– Summer (December – February)

– Varying locations and sizes (using regional PV stats)

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

– Storage of 5kW, 13.5kWh

Key Metrics

– Voltage: Australian Electricity Distribution Code

– Thermal: Asset utilisation (1-hour moving avg)

– Effects on Customers: Grid Dependency


Results: Voltage Issues (LV)

Off-the-shelf (OTS) storage systems help…but to a limited extent


Results: Thermal Issues (HV)

LV networks are pretty robust

Off-the-shelf (OTS) storage systems help…but to a limited extent


Why are they unable to help?

Most storage systems are full when network problems occur

All available generation is absorbed + no adequate discharging overnight= high SOC early morning


… To what extent can a ‘smart’

storage control help?


Optimization-Based Control

It determines the daily optimal operation (QP) for the storage system to reduce/flatten grid power imports and exports

– Local information, perfect demand/generation forecast

One customer (5kWp PV System, 5kW 13.5kWh battery)

PV Only OTS OPT

SOC full

High exportsImports/Exports

are flat


Deterministic Results(100% PV)

PV Only OTS OPT


Probabilistic Results

Effective mitigation of voltage and thermal problems


… But what about the

customers?


Grid Dependence Index (GDI)

Effect of using storage on the electricity bill

𝐺𝐷𝐼 =𝑖𝑚𝑝𝑜𝑟𝑡𝑠

𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛

100% - household totally grid dependent (normal bill)

0% - household totally grid independent (no bill)

Grid

Household

consumption


Grid Dependency

Adequate control actions can benefitboth network and customers


… What about system-level

challenges?


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Aggregated Net-Demand ProfilesPV Only

Reverse power flows (22kV66kV)

Slightly reduced peak demand

!

Residential + Commercial


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Aggregated Net-Demand ProfilesPV + OTS Storage

Reverse power flows (22kV66kV)

Much less peak demand

!



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Aggregated Net-Demand ProfilesPV + OPT Storage

No reverse power flows (22kV66kV)

Demand is reduced throughout the day



… so, it is just a matter of

‘smart’ control

… not really


Flexibility Vision (UK Regulator)

TRANSMISSION NETWORK

DISTRIBUTION NETWORK

Renewable generators

conventional thermal generation

INDIVIDUAL PROVIDERS

Changing demand/supply in response to prices or direct signals from flexibility users.

LOCAL BALANCING

Community-based flexibility where consumers use local generation with DSR or storage, reducing the need to transport electricity.

THIRD PARTY AGREGGATION

Consumers, generators and storage can provide flexibility through an intermediary. Based on Ofgem’s

vision of flexibility


Flexibility Vision (Australia)

“Instead of building networks ‘buy’ output from DER (through retailers, aggregators or directly from customers) for locational, dynamic benefits”


Bottom-Up Flexibility: D T

Opportunities for the provision of flexibility services from distribution-connected resources

– From individual customers or aggregators

– To TSO or, in the future, to DNSPs

Resources:

– PV + Storage

– Electric Vehicles

– Demand Response

– etc.

… and who coordinates all this?

T D


Smart & Low Carbon

Bulk Generation

Homes, Schools, Shops, Businesses,

Communities

Distributed Generation

New Service Markets

$

Storage

Distribution

System Operator


… Why is this so challenging?


Current Control Philosophy(Distribution)

Grid Supply Point (GSP)

No control of LV and part of HV

Bulk Supply Point (BSP)

Primary Sub

DNSP Control Room

OLT

C

Swit

ches

OLT

C

OLTCs Coordinated Decentralised Control

Secondary Sub

Centralised Monitoring and ControlReconfiguration Manual (Remote)

Voltage Decentralised (Fixed Targets)

OLT

C

Swit

ches

Reconfiguration Manual (Local)Voltage Off-load taps


Fully Centralisedvs. Coordinated Decentralised

Fully Centralised

– Opportunity for holistic ‘optimisation’

– Full flexibility

– Increased reliance on monitoring/comms

– Increased complexity due to scale

– High deployment time

Coordinated Decentralised

– More localised ‘optimisation’ (static areas)

– Flexibility exists to centrally react to problems

– Less centralised monitoring/comms

– Less complexity due to reduced scale

– Less deployment time


… but there are many other barriers

DSOs should be capable of

– Quantifying operational needs and constraints (across voltage levels)

wide-scale observability, forecasting

– Exchanging data with the TSO and third parties (flexibility providers)

Defining Distribution Markets

– Voltage management, congestion management

– Near or post fault management (enabling islanding/microgrids)

… all this requires advanced management systems, investment, time, training, etc.


Conclusions 1/2

PV-rich communities place significant technical (and economical) challenges to DNSPs

– Simple solutions (e.g., off-LTC) might not be enough to deal with high PV penetrations

– Residential PV + storage might become more viable

Customer-focused storage control strategies might not reduce PV impacts

– Storage gets full before critical periods (around midday)

– This, however, depends on the network design

New storage control strategies can mitigate network impacts from PV without affecting customers


Conclusions 2/2

Complexity will increase with more controllable elements and the need for more flexibility

– Computational/data complexity shouldn’t be an issue in ~15 years

Regulators need to define the roles and responsibilities of players and technologies in the provision of flexibility

– E.g.: aggregators, storage

– This will prevent new business models being hindered by regulatory barriers

This transition of DNSPs to DSOs in the next few years will bring exciting new regulatory environments where the envisioned smart grids are likely to finally emerge


DSOs - Further Reading

1. L.F. Ochoa, F. Pilo, A. Keane, P. Cuffe, G. Pisano, “Embracing an adaptable, flexible posture: Ensuring that future European distribution networks are ready for more active roles,“”IEEE Power and Energy Magazine, vol 14, no 5, p 16-28, Sep/Oct 2016 (http://dx.doi.org/10.1109/MPE.2016.2579478)

2. Council of European Energy Regulators, “The future role of DSOs—A CEER conclusion paper,” Brussels, Belgium, Tech. Rep. C15-DSO-16-03, Jul 2015

3. Office of Gas and Electricity Markets, “Making the electricity system more flexible and delivering the benefits for consumers,” London, UK, Sep 2015

4. evolvDSO Project, “Development of methodologies and tools for new and evolving DSO roles for efficient DRES integration in distribution network” (http://www.evolvdso.eu/)

http://dx.doi.org/10.1109/MPE.2016.2579478

http://www.evolvdso.eu/



https://www.ofgem.gov.uk/publications-and-updates/position-paper-making-electricity-system-more-flexible-and-delivering-benefits-consumers

https://www.ofgem.gov.uk/publications-and-updates/position-paper-making-electricity-system-more-flexible-and-delivering-benefits-consumers


Technical Reports and Publications

Technical Reports (most publicly available):

https://sites.google.com/view/luisfochoa/publications/technical-reports

List of Publications (most publicly available):

Journal Papers

https://sites.google.com/view/luisfochoa/publications/journal-papers

Conference Papers

https://sites.google.com/view/luisfochoa/publications/conference-papers

https://sites.google.com/view/luisfochoa/publications/technical-reports

https://sites.google.com/view/luisfochoa/publications/journal-papers

https://sites.google.com/view/luisfochoa/publications/conference-papers


Thanks!

Questions?

Acknowledgement

• Dr. Andreas ProcopiouResearch Fellow

• Mr. Kyriacos PetrouPhD Student


PV-Rich Communities, Storage, and Flexibility: The Need for DSOs

15th May 2018

SBSE 2018, Niteroi - RJ, Brazil

Prof Luis(Nando) Ochoa

IEEE PES Distinguished Lecturer

Professor of Smart Grids and Power Systems

[email protected]

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