Discussion Document: Energy Storage and Power Electronics on the Low Voltage Distribution Network

Problem statement, hypothesis and test deployment programme

1. Introduction

New Thames Valley VisionThe New Thames Valley Vision (NTVV) aims to demonstrate that understanding, anticipating and supporting changes in consumer behaviour will help DNOs to develop an efficient network for the low carbon economy. This £30 million project is part of a £500 million programme funded by the Low Carbon Network Fund (LCNF) run by Ofgem, the UK energy regulator.

Learning OutcomesThe project explores five central learning outcomes:

1 Understanding - What do we need to know about customer behaviour in order to optimise network investment?

2 Anticipating - How can improved modelling enhance network operational, planning and investment management systems?

3 Optimising - To what extent can modelling reduce the need for monitoring and enhance the information provided by monitoring?

4 Supporting Change - How might a DNO implement technologies to support the transition to a Low Carbon Economy?

5 Supporting Change - Which commercial models attract which customers and how will they be delivered?

Through the deployment of energy storage and power electronics the project will specifically explore questions centred on learning outcome four, these are:

4.1 How could distributed solutions be configured into the DNO environment?

4.4 How would network storage be used in conjunction with demand response?

Energy Management TrialsIn the 2011 project bid submission NTVV identified a number of applications for energy storage and power electronics that explore their use as ‘network side’ solutions to enable more effective use of the existing network in accommodating the transition to a low carbon economy. Further details and extracts of the project bid submission are contained in Appendix 1.

Successful Delivery Reward CriteriaThis report is written to develop and clarify the trials of energy storage and power electronics in the New Thames Valley Vision. In compiling this discussion document, the project is fulfilling Successful Delivery Reward Criteria (SDRC) 9.4a

CRITERION: Develop problem statement, hypothesis and test deployment programme for coordinated energy storage and power electronics on the Low Voltage distribution network - building on previous and current battery installation tests

EVIDENCE: Produce discussion document and deployment plan for energy storage and power electronics – include an assessment of the management of network losses and power quality

2. Problem Statement

Changing customer requirementsNetwork demand will change as individuals, small businesses and larger companies act either on their conscience or in response to economic stimuli, to reduce their carbon footprint. The action customers take will have many forms including: energy efficiency measures; the installation of solar thermal or photovoltaic (PV) panels and other small-scale renewable energy devices; and an increased uptake of electric vehicles. The New Thames Valley Vision looks to support changes in our customers’ energy behaviour as they move towards low carbon technology.

DECC's UK Low Carbon Transition Plan portrays a number of possible paths for the evolution of energy use as the low carbon economy advances. The document considers the impact of a range of potentially disruptive technologies capable of changing the scale and nature of energy flows on the network, including:

Electric cars Supplier drive demand side management Heat pumps Micro Generation Electrification of heat Electrification of transportation

These, amongst other factors, will have the effect of disrupting the predictability of maximum demands and profiles that have heuristically evolved over the last few decades. These demand profiles are the centre of our existing planning methodologies yet within the next few years will be of diminished value as the nature of load flows become more dynamic.

Better understanding of changing requirements through NTVVThe NTVV is developing new tools and techniques to better understand the changing energy requirements of customers connected to the Low Voltage network. By aggregating and statistically grouping the modelled profiles of individual customers on each feeder the project will develop feeder power flow profiles. These will be validated against monitoring data from this project and other LCNF projects (to the extent that this data is made available) to identify whether behavioural trends can be drawn.

The project will create an agent-based forecasting model to enable short, medium and long-term demand predictions with envelopes of uncertainty. It is anticipated that take up of low carbon technology will not be uniform across customers, and hence neither across LV networks, but more sporadic in clusters. The forecasts will be designed to account for this non-uniformity. A key feature of both the modelling and forecasting techniques under development is that they are expected to be applicable to, and have sufficient resolution for DNO purposes, regardless of whether smart meter data is available from every household and small business in the country.

Technical Standards and EfficiencyElectricity network customers can expect a regular and reliable supply of electricity which is capable of meeting power requirements within defined characteristics. The design and operation of our low voltage network ensures the network remains within a number of technical standards concerning voltage and thermal capacity. Each of these criteria has an impact on design and operation and is impacted as network usage changes. Economic and moral drivers dictate that networks should operate efficiently, where efficiency seeks to maximise utilisation and minimise loses at the lowest overall cost. These standards and drivers are described in more detail in Appendix 2

VoltageThe low voltage network is built with fixed transformer tapping ratios at the supplying 11kV/LV distribution substation with dynamic voltage control at the 11kV busbars of a primary substation only. The dynamic control seeks to maintain all connected customers within an acceptable voltage range but does not attempt to manage voltage variations for periods shorter than 1 minute.

Networks are designed to manage voltage with respect to: regulation, harmonic distortion, balance and flicker. Traditional engineering approaches for addressing poor voltage performance seek to: isolate ‘dirty’ loads, reduce current flow and/or reduce network impedance. Under all three of these approaches the network is not utilised at full thermal capacity and the connection of new loads or generation may be delayed until additional network assets can be installed. Clearly the installation of new network assets is a costly, disruptive and carbon-intensive operation.

Thermal CapacityElectrical assets have finite thermal capacities beyond which their insulation performance deteriorates - excessive heat will cause an asset to fail. In a low voltage poly-phase cable the thermal capacity is the combined effect of all phase and neutral conductor limits

The traditional engineering approach for addressing poor thermal performance seeks to: distribute demand/generation evenly across phases at construction or during operation, if possible; split-up heavily congested networks by introducing additional interconnection; or overlay sections of reduced capacity. As with the traditional methods for addressing voltage performance, the above approaches require network reconfiguration and/or new asset installation which can be costly, disruptive and carbon-intensive operation.

UtilisationThe load-factor for the average low voltage customer1 utilises only 3% of service cable capacity throughout the course of the year. To scale this up to the distribution network implies that the wider network is similarly under-utilised whilst simultaneously close to capacity in terms of instantaneous thermal and voltage limits

Since the traditional engineering approach for utilisation is not able to store energy at a local level, there is no scope to improve the utilisation of the network. With increased deployment of low carbon technologies, the network may be required to deal with even greater peaks for which the only traditional solution to maintain technical performance would be the creation of extra capacity and further reduction in utilisation

LosesThe technical2 losses of a distribution network are a function of current flow through shunt and series impedances. Series losses are result in ‘real’ power lost from the system and constitute the largest contributor, these losses increase in proportion to the square of current flow. Shunt losses are entirely reactive but affect network performance by causing increased current flow and impacting voltage regulation. Analysis of the losses in a typical SSEPD GSP network3 identified that 2.4% of the energy supplied was lost in local low voltage distribution

The traditional approach to technical loss reduction seeks to reduce network impedance through the installation of additional capacity and by attempting to balance connections across all phases. Both of these options are costly and disruptive. A proportionately greater improvement could be achieved by reducing peak current flow – however since traditional networks cannot store energy, this would be entirely at the discretion of the customer.

1 Taking the weighted average of profile-class half-hourly consumption data for the Botley Wood GSP as assessed over the 2007-2008 period.2 Technical loses exclude losses as a result of metering or billing inaccuracies and theft3 For the network connected from Botley Wood GSP as assessed over the 2007-2008 period

3. Solution

Power Electronics and Energy StorageThe New Thames Valley Vision will deploy power electronics and storage to allow the existing network to respond more flexibly. This will maintain the network within the technical standards identified above whilst also maintaining or improving the efficiency of the network as customers change their energy behaviour as they take up low carbon technologies.

ApplicationsThe following applications will be trialled to support the technical requirements (identified above). In this table, the anticipated benefit is marked as ‘high’ where a direct improvement is expected and ‘medium’ where an indirect or consequential improvement is likely.

Voltage Thermal Efficiency

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1. Balancing load between phases (without storage)Power electronics configured to a common DC busbar to allow dynamic redistribution of current from one phase to another to either equalise loading or manage voltages. This would result in reduced current flow peaks on the most loaded phase and address thermal constraints but would also have consequential improvements to efficiency and voltage regulation.

M M H H M M

2. Storage to balance peaks and troughsApplication of storage and forecast energy consumption to optimise network utilisation within a specific capacity. Would have an impact on the directly connected LV circuit and also, in combination with other units on local substation and associated HV circuits. Direct benefits to thermal and efficiency measure with an indirect improvement in voltage regulation.

M H H H H

3. Balancing load between phases (with storage)Combination of (1) and (2) above to allow optimisation across phases with additional capacity as enabled by spreading peaks and troughs across time.

M M H H H H

4. Reactive voltage support (without storage)Use of power electronics to modify current waveforms to adjust reactive component of load. Would result in increase to overall demand on circuit either from the same phase or adjacent phase. Reactive component use to counteract reactive volt-drop, mostly as a result of distribution transformer impedance.

H H M

5. Reactive voltage support (with storage)As above, with the ability to use stored energy to alter reactive component without increasing overall instantaneous current on the basis that the energy store can be charged at some other convenient time.

H H M

6. Improve power quality & harmonicsUse of power electronics to act as active harmonic filters to identify and generate

H H

mitigating currents to improve power quality and harmonic limits.7. Demand reductionUse of reserve energy storage capacity to reduce demand during planned or fault outage to enable continuity of supply.

H

8. Frequency responseUse of reserve energy storage capacity to react to over or under frequency events by absorbing or releasing power. This would support the system operator’s duty to maintain frequency and would help customer maintain electricity during national frequency events

H

Traditional Network ReinforcementAs identified above, the traditional approach to maintaining the technical standards for voltage and thermal limits results in physical interventions to either increase capacity or reconfigure connections, where possible. Whilst these solutions remain valid, they do not necessarily encourage good network efficiency and are disruptive, slow to instigate and have a significant carbon impact.

To benchmark and asses the effectiveness of power electronics with energy storage, the NTVV will consider the implications of the main alternative, which is to do nothing new.

As the 2011 project bid submission identified, the most challenging part of replacing distribution assets would be at low voltage level, with the upheaval and cost of replacing individual service cables, substations and associated plant. The replacement value for the complete renewal of these assets just for SSEPD's two licences would be circa £3 billion.

Operational ManagementOther than reinforcement, networks can seek to apply operational measures to manage changing network performance. It typically takes around 3 to 4 months from recognition of the need to reinforce an LV feeder to completing that reinforcement. During this time customers' generation is likely to be tripping out on G83 protection (if there is an excess of generation connected) or LV network fuses are likely to blow (if there is an excess of HP or EV connected). This would not be remedied by the deployment of automatic replacement fuses such as the Bidoyng.

Increasing Requirements for Customer Equipment PerformanceAll equipment which connects to the Distribution Network must meet certain standards such that it does not unreasonably affect other customers connected to that network. This may be of particular relevance to harmonic performance. As an alternative to network reinforcement there may be relative merits in insisting on higher harmonic standards from appliances installed by customer.

Benchmarking CostsFrom SSET 1008 LV Connected Batteries project, we have learnt that Energy Storage and Power Electronics can be expensive assets to deploy. Whilst we expect the cost of units to decrease as the technology matures and as greater economies of scale are realised, at present it does not seem feasible that units designed to address just one technical requirement would justify their deployment.

However, raw cost aside, Energy Storage and Power Electronics demonstrate the potential to exceed the performance of traditional reinforcement with respect to speed of deployment, level of disruption, coordinated improvements in technical standards and improved network efficiency.

The costs of energy storage and power electronics are broadly split as follows: Energy storage 80% of the cost Power electronics 20% of the cost

Therefore the challenge in driving economy is to combine multiple functionality into a single unit such that the same installed assets are able to simultaneously address a variety of technical standards. Likewise, improvement which can be realised using the electronics alone should be explored and delivered in such a way that allows storage to be added as and when economic.

4. HypothesisFrom a consideration of the Problem Statement in section 2 and the Solutions identified in section as supported by the findings to date in SSET 1008 LV Connected Batteries project has drawn the following hypothesis:

Economic and flexible support for LV networks will be provided by power electronics with energy storage running smart control algorithms which make use of forecasted demand to provide a coordinated response to addresses the technical standards of voltage and thermal performance in the most efficient manner possible.

5. Test Deployment ProgrammeTo assess the hypothesis of section 4 the NTVV has developed the test plan detailed in this document. The following summary illustrates the linkages between the hypothesis and the test plan.

Summary

Hypothesis statement Test Plan

“… for LV networks…”

LocationThe fundamental aim of NTVV is to better understand and anticipate customer behaviour, which will help to reduce the uncertainty about future demands on distribution networks. The Thames Valley is considered to be an ideal location for such a project due to the 'ordinariness' of the network. The distribution system has no unique features; is of average age and reliability; has no significant low carbon initiatives in the area and no eco-towns. In short, it is typical of much of the UK. We believe therefore that the findings from NTVV will be applicable to much of the country and thus the learning useful to all DNOs.

“Economic and flexible support…”“… most efficient manner possible…

Assessment criteriaDistribution networks are built to serve the needs of their customers and as customers move to lower carbon technologies, the networks will need to adapt so that the same reliable levels of service can be maintained. Through the assessment of Energy Storage and Power Electronics alongside traditional reinforcement the NTVV will assess the comparative benefits of:1. Cost2. Speed of deployment3. Level of disruption4. Impact on technical standards (per standard and in combination)5. Impact on efficiency

“… the technical standards of voltage and thermal performance…”“… coordinated response…”

Network impactThe project will trial energy storage and power electronics units with the ability to operate the flowing functions in combination:1. Balancing load between phases (without storage)2. Storage to balance peaks and troughs3. Balancing load between phases (with storage)4. Reactive voltage support (without storage)5. Reactive voltage support (with storage)6. Improve power quality & harmonics7. Demand reduction8. Frequency response

As identified in section these functions will provide varying degrees of support to: Voltage – regulation, harmonic distortion, balance and flicker Thermal Limits – phase and neutral Efficiency – Utilisation and Losses CI/CML and Emergency response

A central theme of the hypothesis and test plan is to assess the ability or otherwise of control algorithms to optimally dispatch these different requirements.

“… smart control algorithms which make use of forecasted demand…”“… coordinated response…”

Control environmentThe NTVV is developing algorithms to analysis and forecasts future energy consumption on the low voltage network in Bracknell. The Energy Storage and Power Electronics test plan will take advantage of this data and will assess its application in the practical control of field dispatched units.To facilitate this, the NTVV will deploy battery units which pass all

relevant metrology from power electronics and energy storage along with other network information back to central system. The central control scheme then simulate various control level of control authority including ‘simulation’ of local control within the unit and also agent based communication between units

Staged Deployment Plan

1. Refine specification, design and tender Oct-12 to Jun-13a. Define functional and non-functional requirements of power electronics and energy storage units – to include

1. Balancing load between phases (without storage), 2. Storage to balance peaks and troughs, 3. Balancing load between phases (with storage), 4. Reactive voltage support (without storage), 5. Reactive voltage support (with storage), 6. Improve power quality & harmonics, 7. Demand reduction and 8. Frequency response

b. Define functional and non-functional requirements of control scheme: What functions require external control (i.e. can frequency response be a locally defined set-point)? Where is control best placed – locally, centrally does this vary by function? Finite capacity, on what basis should inverter and storage capacity be deployed to best support each of the identified functions?

c. Define optimisation problem: if the variables are known (into the future) then what potential is there for these to be optimised but how is uncertainty managed; what non-network variable also need to be considered (i.e. maintenance of battery lifespan)

d. Define physical dimensional limits for deployed units – draw on Tier 1 Battery Storage findings and support with site surveys and consultation with Highway authority.

e. Tender of power electronics and energy storage unitsf. Tender communication provider

2. Development of smart control algorithms  Jan-13 to Mar-14a. Smart control algorithms will be developed for individual storage devices to achieve specific applications

(peak demand, voltage regulation etc.) using the aggregated forecast for the location of the storage devices.b. The algorithm will take into account the storage devices specifications (battery size, charge and discharge

rate etc.) and constraints that will maximise the life of the storage devices.c. Distributed control algorithms, such as multiple agent systems, will be developed for deployment to the grid.

These algorithms will ensure that storage devices are able to work together in order to achieve specific applications (peak demand, voltage regulation etc.)

d. Control Methods will be implemented and simulated using the aggregated forecast and actual smart meter data.

3. Construction of power electronics and energy storage units Jul-13 to Dec-13

4. Installation of power electronics and energy storage units Jan-14 to Jun-14a. Type test units away from site to assess safe performanceb. Complete civil worksc. Commission units to networks

5. Installation of communication infrastructure Jan-14 to Jun-14a. Commission to control systemb. Commission to power electronics and energy storage units over communication to control system

March 2014 - SDRC 9.4c Install 25 LV connected batteries

6. Test functional deployment without smart control algorithms (under supervision) Apr-14 to Sep-14a. Assess performance of unit for each of the separate network functionsb. Assess performance of unit for combinations of separate network function

November 2014 - SDRC 9.8a(4) Report into LV Network Storage

7. Deploy smart control algorithms to simulated network Apr-14 to Dec-14

8. Test functional deployment with smart control algorithms (under supervision) Jan-15 to Mar-15a. Assess performance of unit for each of the separate network functionsb. Assess performance of unit for combinations of separate network function

March 2015 - SDRC 9.4d - Produce learnings from energy storage and power electronic deployment to assess the hypothesis.

9. Operate units under smart control without supervision Apr-15 to Sep-15

10. Reduce the amount of forecast and ‘live’ information available to units Oct-15 to Mar-16a. Reduce the degree of information available to algorithms – noting that algorithms will be hosted centrally

though simulating varying degrees of local control. This approach maintains central control in the event of poor algorithm performance

11. Operate units with reduced central control Oct-15 to Jun-16a. Develop agent based control algorithmsb. Simulate algorithmsc. Deploy simulation of agent based control using central control scheme

12. Analysis Jul-16 to Sep-16a. Review schemes performance against traditional reinforcement methods and/or increased requirements of

customer equipment performanceb. Assess benefits with respect to 1. Cost, 2. Speed of deployment, 3. Level of disruption, 4. Impact on technical

standards (per standard and in combination) and 5. Impact on efficiency

13. Identify future applications - desk top analysis of applicable findings in relation to other aspects of controllable demand Oct-16 to Dec-17

a. Automatic Demand Reposeb. Thermal hot storage to manage PV (i.e. EMMA units)c. Thermal cold storage in conjunction with Building Management Systems

Appendix 4 contains a Gantt chart of this programme

Building on previous learningSSEPD has gained and is developing a broad experience of energy storage and in particular battery systems. The NTVV will build on the learning across a range of project with a focus on the Tier 1 project ‘SSET 1008 LV Connected Batteries.’ From this previous learning, we are able to build on:

Full safety case and risk assessment which focuses on the installation and operation issues relating to energy storage with a particular emphasis on Lithium-Ion technology. The document makes reference to the potential hazards, the mitigations in place and the relevant standards and directives the devices must comply with.

The commissioning process has been detailed and recorded from the basic start up tests from the manufacturer right through to the G59/2 testing.

A detailed test plan to cover initial safety and operational tests moving into detailed functionality testing over a 12 months period

Communications integration in relation to the radio communications between the batteries and a control hub and from the hub back to the SSEPD control system in the control room at Portsmouth.

Appendix 3 explores the key findings to date that are relevant to the NTVV.

Indicative Energy Storage and Power Electronics UnitsWhilst the plan allows for detailed design and refinement followed by a period of tender, the following indicative designs have been developed:

TechnologyDeploying energy storage on the low voltage network requires a high energy density medium to provide high power without necessitating a large amount of space. This requirement means the most likely technology is a lithium chemistry based battery.

Form-factorIt is proposed to design a modular and scalable solution which will allow the power electronics to be deployed with or without the associated storage, with additional storage added later if required. We will work with the local authority to ensure the physical dimensions can be accommodated within the built environment.

Power ElectronicsInverter electronics can be configured with 4, 6 or 12 gates – where 4 gates provide single phase operation, 6 gates allow balanced three-phase operation and 12 gates would allow independent operation of three-phases. It is proposed to use three phase with 12 gate inverters to allow the full range of functions as identified in section 3. Subject to tender, we propose to deploy only three phase units but with the functionality to operate with only one phase live. This would be a departure from the original 2011 bid submission which indicated an even mix of single and three phase units. A final decision of the mix will be informed by detailed specification and tender in the context of the project hypothesis.

SizingLithium technology can be expensive to procure, with the DC element of the system making up approx 80% of the cost of a single hour capacity unit. We will draw on the SSET 1008 project is to prevent the storage units being over sized. To ensure compatibility and ongoing operation and maintenance, it is proposed to size units to match standard distribution network infrastructure and hence inverters are expected to have a 20kW peak output to match the sizes of a typical 100A service connection.

Appendix 1Summary and extracts from 2011 bid submission

Thematic Summary

In the 2011 project bid submission, NTVV identified the following applications and delivery factors for power electronic converters and energy storage as ‘network side’ to support the transition to a Low Carbon Economy.

Applications(a) Without energy storage

Control voltage along a circuit - Static VAr Compensation (SVC)/four quadrant operation Balance phases Reduce losses to gain maximum network benefit from embedded generation Improve power quality and harmonics management

(b) With energy storageThe primary objectives of this element of the project are to: Reduce peak demand on the LV network (demand and generation)

o The battery units will be used to peak lop both demand and generation under theoretical cable limits thereby demonstrating the effectiveness of the technology without affecting the security of supply

Negate the need for traditional network reinforcement

The secondary objectives of this element of the project are to: Quantify the effect on the high voltage network of reducing the peak demand at low voltage level Stop network constraints limiting the connection of LCT to customers on the low voltage network Understand the economic case for energy storage as an alternative to traditional reinforcement (reactive)

and as tactical buffer in advance of predicted LCN installation (pro-active) Appreciate the technical implications of installing a large array of inter-connected energy storage units Understand how storage could continue to provide power to customers during fault conditions (possibly

under constraints) until restoration can occur

(c) Additional project applications In the initial stage of NTVV we intend to use the smaller domestic storage facilities to

o simulate the effect of low carbon technologieso 'stress-test' the facilities' ability to help balance networks.

Delivery To demonstrate robust understanding of how a DNO can effectively deploy and operate this technology to

support customer choice. This will build on learning acquired from three single-phase units installed as part of the ‘LV Connected Batteries’ IFI project

Test metricsBy March 2014 - Install 25 LV connected batteries >30 power electronic converters on the LV network, may/not be associated with electrical energy storage 15 single-phase (10kW/10kWh) 16 three-phase (25kW/25kWh)

Extracts from Project Submission and Appendix

NTVV will evaluate solutions including: … low voltage (LV) static voltage control; street level energy storage; and a range of communications solutions [Project Submission: Page 1, Section 1.3]

Objectives … [number] 3... Demonstrating mitigation strategies... b. Where and how power electronics (with and without energy storage) can be used to manage power factor, thermal constraints and voltage to facilitate the connection of renewables on the LV network [Project Submission: Page 2, Section 2]

Methods... 4... Tactically deploy power electronics and electrical energy storage on the low voltage networks... Finally, we will deploy power electronics and electrical energy storage on low voltage networks as a tactical 'buffer'. This will demonstrate the extent to which these technologies could manage power factor, harmonics and voltages to provide a fast and flexible alternative ensuring customers have the freedom to deploy low carbon technologies without waiting for time-consuming reinforcement (or their alternatives) to take place. All of the technical solutions outlined above will be fully integrated into the distribution network control room. [Project Submission: Page 3, Section 2]

…Although better understanding of customers and of network feeders can reduce the need for premature reinforcement, when LCT connections have used up the true available headroom it will be necessary to reinforce. In some cases this may be reactive… Chalvey LCNF T1 monitoring project has highlighted that a precursor of thermal and voltage constraints will often be power quality issues of power factor and harmonics... We will demonstrate how power conversion power electronics can be used to manage these issues with and without energy storage modules at the LV network… supported by Imperial College… [Deploying] statistically relevant quantities. This will provide a robust understanding of how a DNO can effectively deploy and operate this technology to support customer choice. A total of 15 single-phase (10kW/10kWh) domestic storage units and 16 three-phase (25kW/25kWh) street storage units are planned in the NTVV project. Energy storage units will be used to peak lop both demand and generation to keep supplies within cable limits. The devices also have the capability of four quadrant operation, meaning it is possible to provide voltage support to keep the supply within the given standards. [Project Submission: Page 7, Section 2]

In the initial stage of NTVV we intend to use the smaller domestic storage facilities to simulate the effect of low carbon technologies - 'stress-testing' the LV network." [Project Submission: Page 7, Section 2]

Supporting change through deployable solutions… On the network side we will deploy LV connected electrical energy storage and power electronics, in statistically relevant quantities. This will provide a robust understanding of how a DNO can effectively deploy and operate this technology to support customer choice. Integration is key - both the customer side and network side solutions will be linked to the DNO's control room to provide a robust end-to-end control system. [Project Submission: Page 4, Section 2]

Generic activities of DMSo GE's DMS will act as the coordination hub for network management which will integrate with various intelligent distributed energy resources to be deployed in the LV network, leading with demand resource and battery storage resourceso The ability to calculate where and when additional resources can be used to re-enforce the current network during peak demand timeso The ability to charge LV storage units during off-peak times in order to make them available during peak times without impacting current demando The availability of power analysis information based on load profiles for estimation of current system demando The availability of power analysis information based on substation monitoring information available from the monitoring solution detailed previouslyo The ability to link into the Honeywell ADR as an aggregator of demand response across an estate of buildings to create a despatchable demand resourceo Systematic evaluation of telecommunications solutions in NTVV and other available projects[Project Submission: Page, Section 2]

… potential to enable the network to continue to provide power to customers during fault conditions (possibly under constraints) until restoration can occur, reducing customer interruptions (CI) and customer minutes lost (CML). Additionally they potentially could be used to avoid significant network reconfiguration under fault conditions… Energy storage could provide local power to support the local network… Building Management Systems could have an 'emergency' setting where all but essential load is switched off, enabling the network to continue to operate at significantly reduced capacity for a time… Rapid deployment of storage in the event that several EVs or HPs connect into a given street will enable customers to use these technologies without causing overloads of local network assets and avoiding local loss of supply due to the operation of circuit protection. [Project Submission: Page 21, Section 4(c)]

Learning Outcomes and associated project trials description

LO-4: Supporting Change - How might a DNO implement technologies to support the transition to a low carbon economy?[Project Submission: Page 24, Section 4]

Focusing on the technical solutions for managing the effects low carbon technology is likely to have on a distribution network. All network mitigation techniques rely upon the deployment of appropriate solutions such as the conventional network assets; novel network assets; or novel customer side solutions. NTVV will focus on the integrated application of two key solutions, one on the network side and one on the customer side, in a range of scenarios. On the network side, electrical energy storage will be deployed in statistically relevant quantities and managed at key locations and working with Honeywell on the customer side NTVV aims deploy 30 demand management systems.

LO-4.1 How could distributed solutions be configured into the DNO environment[Project Submission: Appendix page 11 (page 64) onwards]

The distributed technology solutions we are concentrating on for NTVV are: Use of power electronic converters (with and without electrical energy storage): a network-side solution that

can be applied to LV networks, and in some instances rolled out to customers’ premises Building management systems (BMS): a customer-side solution for large and (potentially) light commercial

customers. This will also include the use of two variants of thermal storage.

Use of power electronic convertersThe power electronic converters typically used with electrical energy storage provide a platform to provide reactive power injection to the LV network, allowing the network to be used more effectively without reinforcement. Acting as a form of Static VAr Compensation (SVC), they have the ability to:

Reduce losses to gain maximum network benefit from embedded generation Improve power quality and harmonics management Control voltage along a circuit Potentially balance phases Add energy storage

We intend to deploy over 30 power electronic converters in NTVV. These will all be installed on the LV network, and may or may not be associated with the connection of the electrical energy storage described below.

Use of energy storageNTVV will deploy LV-connected electrical energy storage, in statistically relevant quantities. This will provide a robust understanding of how a DNO can effectively deploy and operate this technology to support customer choice.

A total of 15 single-phase (10kW/10kWh) domestic storage units and 16 three-phase (25kW/25kWh) street storage units are planned in the NTVV project. This will build on learning acquired from three single-phase units installed as part of the ‘LV Connected Batteries’ IFI project (Appendix G) where such storage is connected at the midpoint of a LV feeder circuit supplying SSE’s ‘Low Carbon Homes’ project. The primary objective of the IFI project is to prove the functionality of the battery units, to gain experience of the technology and hence de-risk the larger deployment for NTVV.

The battery units will be used to peak lop both demand and generation under theoretical cable limits thereby demonstrating the effectiveness of the technology without affecting the security of supply. The devices also have the capability of four quadrant operation (provides comprehensive balancing of the network) meaning it is possible to provide voltage support to keep the supply within the given standards. In the initial stage of NTVV we intend to use the smaller domestic storage facilities to simulate the effect of low carbon technologies - 'stress-testing' the LV network.

The primary objectives of this element of the project are to: Reduce peak demand on the LV network Negate the need for traditional network reinforcement

The secondary objectives of this element of the project are to: Quantify the effect on the high voltage network of reducing the peak demand at low voltage level Stop network constraints limiting the connection of low carbon technologies to customers on the LV network Understand the economic case for energy storage over traditional reinforcement Appreciate the technical implications of installing a large array of inter-connected energy storage units

Further to locating electrical energy storage on LV feeders, we aim to introduce micro storage facilities – small batteries - on the low voltage network to simulate the effect of low carbon technologies and 'stress-test' the facilities' ability to help balance networks.

Appendix 2Distribution technical standards and drivers

Technical StandardsElectricity network customers can expect a regular and reliable supply of electricity which is capable of meeting power requirements within defined characteristics. The design and operation of our low voltage network ensures the network remains within a number of technical standards concerning voltage and thermal capacity. Each of these criteria has an impact on design and operation and is affected as network usage changes. These standards are described in more detail in Appendix 2

VoltageThe low voltage network is built with fixed transformer tapping ratios at the supplying 11kV/LV distribution substation with dynamic voltage at the 11kV busbars of a primary substation only. Dynamic control, in combination with fixed ratios further down the network, seeks to maintain all connected customers within an acceptable voltage range but does not attempt to manage voltage variations for periods shorter than 1 minute.

Networks are designed to give performance within the following criteria: Regulation – defined under the Electricity Supply, Quality and Continuity Regulations as 216.2-253V (i.e.

230V +10%/-6%) Harmonic Distortion - Engineering Recommendation G5/4 covers the planning levels for harmonic distortion

and the connection of non-linear equipment to transmission and distribution systems. The phenomena considered in this standard include voltage distortion and voltage notching. Other aspects of voltage distortion are covered in P29 and P28.

Balance – Engineering Recommendation P29 contains the planning limits for voltage unbalance. A voltage unbalance of greater than 1 or 2% can cause unacceptable degradation of equipment if it remains for a prolonged period.

Flicker – Engineering Recommendation P28 covers planning limits for voltage fluctuations caused by industrial, commercial or domestic equipment. Voltage fluctuations are typically caused by motor start-up, arc-welders, blast furnaces and rolling mills. ‘Flicker’ is the visual phenomenon seen (in a fluorescent light bulb) when voltage fluctuations become particularly bad.

The traditional engineering approach for addressing poor voltage performance seeks to:1. Isolate ‘dirty’ loads – segregation of network loads where the characteristics of the load and supplying network

would result in poor performance.2. Reduce current flow – operate the network at reduced utilisation to ensure voltages remain within limits 3. Reduce network impedance – increase assets deployed or connect to alternative network locations to reduce

the impact on voltage as a result of the connected load/generation.

In all three of these cases the network is not utilised at full thermal capacity and the connection of new loads or generation may be delayed until additional network assets can be installed. Clearly the installation of new network assets is a costly, disruptive and carbon-intensive operation.

Thermal CapacityElectrical assets have finite thermal capacities beyond which their insulation performance deteriorates - excessive heat will cause an asset to fail. In a low voltage poly phase ‘mains’ cable the thermal capacity is the combined effect of phase and neutral conductor limits:

Phase conductors carry the current required to service the connected demand or generation. Individual connections may be connected to one or more of the phase conductors on a poly phase cable however the distribution of load or generation across the phases is not necessarily even which may result in one phase carrying significantly more current than the other two.

Neutral conductors carry the summation of all associated phase currents. In a three-phase network, balanced demand or generation will have no resultant neutral current. However, unbalanced loads will result in a neutral current which in combination with significantly leading and lagging reactive connections on different phases and/or third harmonics (on a three phase system) could result in the neutral conductors carrying significantly more than the phase conductors.

The traditional engineering approach for addressing poor thermal performance seeks to:1. Distribute demand/generation evenly across phases at construction2. Re-distribute demand/generation evenly across phases during operation, if possible3. Split-up heavily congested networks by introducing additional interconnection4. Overlay sections of reduced capacity

As with the traditional methods for addressing voltage performance, the above approaches require network reconfiguration and/or new asset installation which can be costly, disruptive and carbon-intensive operation.

EfficiencyEconomic and moral drivers dictate that networks should operate efficiently, where efficiency seeks to maximise utilisation and minimise loses at the lowest overall cost.

UtilisationThe following graph illustrates the load-duration characteristics of domestic customers by profile class (profile classes are the average usage patterns for broad groups of customer type) with a weighted average representative of the typical mix of customers within an SSEPD GSP4. The load-factor for the weighted average profile is only 2.9%, which means if the network is designed to just supply their customer’s maximum demand, then during through the course of the year only 2.9% of the cables capacity would be utilised.

0

1

2

3

4

5

6

Duration

kW

Weighted Average PC01 PC02 PC03 PC04

The above analysis is limited in that customer load usage tends to be more peaky and more sporadic than the typical half-hourly average profile class data shown above and, as such, the network which supplies a number of customers must be built with a significant amount of capacity to meet short duration peaks.

Since traditional engineering approach for utilisation is not able to store energy at a local level, there is no scope to improve the utilisation of the network. With increased deployment of low carbon technologies with, the network will be required to deal with even greater peaks – for which the solution to maintain technical performance would be the creation of extra capacity

LosesThe ‘technical’ losses in a distribution network are a function of current flow through shunt and series impedances. Technical loses exclude losses as a result of metering or billing inaccuracies and theft. Series losses are result in ‘real’ power lost from the system and constitute the largest contributor, these losses increase in proportion to the square of current flow. Shunt losses are entirely reactive but effect network performance through causing increased current flow and affecting voltage regulation.

Slosses=Vi2

Z shunt+ I

o2Zseries

Zseries

Zshunt

Ii Io

Is

Vi Vo

Si So

Analysis of the losses in a typical SSEPD GSP network5 identified that 2.4% of the energy supplied was lost in the local low voltage distribution network as follows:4 For customers connected from Botley Wood GSP as assessed over the 2007-2008 period5 For the network connected from Botley Wood GSP as assessed over the 2007-2008 period

HV/LV Transformer 0.6%LV Feeder 1.5%LV Service 0.0%Meter 0.3%

The traditional approach to technical loss reduction seeks to reduce network impedance through the installation of capacity and by ensuring connections are as balanced across all phases as possible. Both of these options are costly and disruption. A proportionately greater improvement could be achieved by reducing peak current flow – however since traditional networks cannot store energy, this would be entirely at the discretion of the customers’ needs.

Appendix 3Learning from other LCNF projects including SSET 1008

SSEPD has gained and is developing a broad experience of energy storage and in particular battery systems. The NTVV will build on the learning across a range of project with a focus on the Tier 1 project ‘SSET 1008 LV Connected Batteries.’ This section explores the key findings to date that are relevant to the NTVV.

Under SSET 1008, the batteries are deployed as three single phase unit installed as one each phase. This configuration allows units to operate completely independently, e.g. the black phase may be charging, brown phase could be discharging and the grey phase in float mode.

Figure 1.1 shows the electrical connections the batteries as located in relation the distribution substation and the LV feeder circuit.

Figure 1.1 – Network schematic illustrating battery connection point

Figure 1.2 – Battery site layout Figure 1.2 illustrates the site layout under the SSET 1008 trial. The devices are then fed back to a distribution board to allow isolation / switching of the units individually. As can been seen, each battery unit has an interposing transformer convert the battery from 2 x 120V line voltages with a centre tapped neutral to a 240V supply with a live and neutral leg. The interposing transformers and distribution board will not be necessary in the NTVV since, the NTVV will have the opportunity to specify and deploy units designed for the native UK market.

Figure 1.3 – DC element of system Figure 1.4 – AC part of the system

The DC part of the system is contained underground within a fibreglass vault as can be seen in figure 1.3. The AC part of the system along with the inverter / rectifier sits on top of the DC element. The communications and control equipment are also located within the top of the device.

After the physical installation of the devices the units were put through a detailed commissioning programme in order to prove functional operation and comply with the requirements under G59/2. All three units passed the commissioning as required.

The communications between the devices and the control hub have now been proven to function as required and will be further documented within the test plan prior to the functional testing.

At present the civil works are being completed at the site, once this has been concluded the batteries will go into a detailed test programme. The testing will begin with basic charging and discharging, at various power levels. As confidence in the devices increases the testing will become more complex and push the limits of thermal and voltage control on the network. The testing is expected to begin early July 2012 and run for 2 years.

Through delivering SSET 1008, we are able to de-risk the Tier 2 deployment and the following documents have been highlighted to aid the larger rollout:

Full safety case and risk assessment completed by external party EA Technology. The work focuses on the installation and operation issues relating to energy storage with a particular emphasis on Lithium-Ion technology. The document makes reference to the potential hazards, the mitigations in place and the relevant standards and directives the devices must comply with.

Commissioning evidence. The complete commissioning process has been detailed and recorded from the basic start up tests from the manufacturer right through to the G59/2 testing.

Detailed test plan prepared in conjunction with EA Technology. The plan covers initial safety and operational tests moving into the detailed functionality testing over the next 12 months.

Communications integration. Significant work has been completed in relation to the radio communications between the batteries and the control hub and from the hub back to the SEPD Enmac system at the control room in Portsmouth. This work has been documented with screenshots, flow diagrams etc.

Appendix 4Programme Gantt Chart

2012 2013 2014 2015 2016

From To OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1. Refine specification, design and tender Oct-12 Jun-13

a. Define functional and non-functional requirements of power electronics and energy storage units

Oct-12 Mar-13

b. Define functional and non-functional requirements of control scheme Oct-12 Mar-13

c. Define optimisation problem Oct-12 Mar-13

d. Define physical dimensional limits for deployed units Oct-12 Mar-13

e. Tender of power electronics and energy storage units Apr-13 Jun-13

f. Tender communication provider Oct-12 Jun-13

2. Development of smart control algorithms  Jan-13 Mar-14

a. Smart control algorithms will be developed for individual units Jan-13 Mar-14

b. Tailor algorithm for specific specification Jan-13 Mar-14

c. Develop distributed control algorithms such as multiple agent systems Jan-13 Mar-14

d. Implemented algorithms and simulate using the aggregated forecast and actual smart meter data

Jan-13 Mar-14

3. Construction of power electronics and energy storage units Jul-13 Dec-13

4. Installation of power electronics and energy storage units Jan-14 Jun-14

a. Type test units away from site to assess safe performance Jan-14 Mar-14

b. Complete civil works Jan-14 Jun-14

c. Commission units to networks Jan-14 Jun-14

5. Installation of communication infrastructure Jan-14 Jun-14

a. Commission to control system Jan-14 Mar-14

b. Commission to power electronics and energy storage units over communication to control system

Apr-14 Jun-14

March 2014 - SDRC 9.4c Install 25 LV connected batteries 31/03/2014 X

6. Test functional deployment without smart control algorithms (under supervision)

Apr-14 Sep-14

a. Assess performance of unit for each of the separate network functions Apr-14 Jun-14

b. Assess performance of unit for combinations of separate network function Apr-14 Sep-14

November 2014 - SDRC 9.8a(4) Report into LV Network Storage 30/11/2014 X

7. Deploy smart control algorithms to simulated network Apr-14 Dec-14

8. Test functional deployment with smart control algorithms (under supervision)

Jan-15 Mar-15

a. Assess performance of unit for each of the separate network functions Jan-15 Mar-15

b. Assess performance of unit for combinations of separate network function Jan-15 Mar-15

March 2015 - SDRC 9.4d - Produce learnings from energy storage and power electronic deployment to assess the hypothesis.

31/03/2015 X

9. Operate units under smart control without supervision Apr-15 Sep-15

10. Reduce the amount of forecast and ‘live’ information available to units Oct-15 Mar-16

a. Reduce the degree of information available to algorithms Oct-15 Mar-16

11. Operate units with reduced central control Oct-15 Jun-16

a. Develop agent based control algorithms Oct-15 Dec-15

b. Simulate algorithms Jan-16 Mar-16

c. Deploy simulation of agent based control using central control scheme as per 12

Apr-16 Jun-16

12. Analysis Jul-16 Sep-16

a. Review schemes performance against traditional reinforcement Jul-16 Sep-16

b. Assess benefits Jul-16 Sep-16