Low Voltage - Active power control transformer (LV-ACT)
| Funding mechanism | Network Innovation Allowance (NIA) |
|---|---|
| Duration | Aug 2024 - Oct 2025 |
| Estimated expenditure | £555K |
| Research area | Net Zero & Energy system transition |
Objective(s)
Objectives of this project are to determine if this concept is viable, to understand the extent to which the LV-ACT solution can alleviate forecast thermal and voltage constraints and to produce a positive benefits case for the solution. This will be facilitated through delivery of the following outputs:
WP1 - Feasibility and Network Application Studies
- Shortlist of network/feeder archetypes where solution shows benefit.
- Report detailing analysis and results of high-level power flow and voltage profile assessment.
WP2
- Functional Requirements document for the active power control Transformer.
- Detailed design documentation of active power control transformer and communication requirements
- Draft bill of materials for active power control transformer.
- Drawings, Datasheets and Device Models for the Active power control transformer.
- Review of link box switch technology and communication requirements as well as LV distribution board alterations
- Independent review of the active power control transformer and two winding HIT.
WP3
- Detailed network models for Power system studies.
- Results of power systems analyses, duration and level of active power control required
- Impact of active power control and feeder meshing on other network aspects, i.e. voltage, power factor, fault levels etc
- Cost benefit analysis of active power control transformer solution using Transform
- Cost benefit analysis of two winding HIT providing voltage control only.
- Comparison of active power control transformer with other BaU and Novel solutions.
WP4
- Final design and bill of materials for benchtop prototype.
- Prototype testing plan
- Prototype testing results
- Device Control panel factory acceptance testing
- Device transformer IEC factory acceptance testing
- Independent review of prototype testing
- Recommendations for further project phases
- Project closedown report
Problem(s)
ED2 business plans and network modelling, along with the outcomes of our recent innovation project SILVERSMITH, forecast that a significant portion of the LV network will experience voltage rise, transformer and cable thermal constraints, exacerbated by the increased uptake of LCTs. Certain LV feeder archetypes will experience transformer and cable thermal constraints by the early to mid-2030s while voltage constraints are expected to affect LV feeder archetypes even sooner.
Whilst we are able to resolve these issues using conventional means and other recently developed novel technologies, there are significant restrictions and issues with the wide-scale deployment of these solutions, such as cost, disruption to customers or physical space constraints.
This project will explore and develop the use of a novel transformer technology alongside feeder meshing. The solution will aim to resolve voltage and/or thermal constraints out to 2050 and be deployable within the existing footprint of a secondary ground mounted transformer, thereby aiming to increase the number of probable deployments.
Method(s)
A novel transformer will be designed and pending successful completion of stage gate 1, a prototype developed, to assess its’ ability to independently control active power flow in two feeders, either from the same substation (looped) or from adjacent substations (meshed). Load sharing will be facilitated, thereby removing constraints from one feeder by transferring load to another unconstrained feeder, while also controlling the voltage profiles along the feeders. Network modelling will be completed to validate the outputs from the active power control transformer model within meshed/looped networks. The meshing/looping of LV feeders will not be physically tested as part of this project. In addition to this, an existing smart hybrid intelligent transformer (HIT) which is able to dynamically control its voltage output, will be assessed.
The project will be delivered across four work packages, split across two distinct phases:
Phase 1: Active Power Control Transformer Design and Feasibility Studies
Phase 1 will be a desktop-based feasibility study, including network application studies and the development of an initial engineering design concept. This phase will focus on first considering the technical viability and extent of potential deployment of both the active power control transformer solution and the HIT solution on the network (WP1), before developing a detailed design for the smart active power control transformer (WP2).
This phase will involve the following work packages:
WP1 – Feasibility and Network Application Studies
WP1 will involve exploration of the feasibility and applicability of the active power control transformer on the NGED network.
- Shortlisting of substation archetypes – involving identification of link boxes which are capable of forming a loop between two LV feeders supplied from the same substation, along with those that form a mesh between adjacent substations. Based on a number of categories, the dataset will be categorised into a list of representative substations (archetypes).
- Bounding and input parameters – parameters will be set to ensure analysis is representative of the likely networks that LCT uptake will be considered for.
- Network constraint modelling – analysis of LCT distribution along each of the two feeders will be completed, to determine voltage and thermal constraints that may occur for each archetype. LCT uptake will be applied to representative network archetypes in line with NGED’s DFES studies out to 2050. Using these uptake rates, we will determine voltage and thermal constraints that may occur on these archetypes across a number of years. Estimations will be made with regards to the active power / voltage management that the smart transformer can provide to release capacity and the condition boundaries at which the performance of the smart transformer may become limited.
- Active power flow or voltage control requirements – using the above analysis, the following outputs will be produced for each archetype:
- Quantification of the level of voltage control required to keep the network within voltage rise/drop constraints. o Quantification of the level of passive load sharing achievable through meshing (based on impedance and voltage differences).
- Quantification of the additional active power transfer required to keep the network within operational constraints (based on thermal and voltage limits).
- Initial business case – results from the archetypes in the above analysis will be used to carry out a high-level applicability study of the solution on the NGED network. This will enable a high-level functional requirement for the smart transformer to be determined around the level of active power transfer that would be essential to deliver any value along with how greater transfer could release more value. The number of substations that could benefit from voltage control using the HIT along with the potential duration of any reinforcement deferral due to alleviation of voltage constraints will be determined. Taking this data, analysis will be carried out to scale the potential opportunity across all of the longlist substations initially identified based on the archetype assignment
WP2 – Functional Requirements and Solution Development
WP2 focuses on the design of the smart active power control smart transformer (ACT), alongside independent review of the existing hybrid intelligent transformer (HIT).
- Concept development – ACT objectives, network and technical requirements will be defined. Functionality of the device system and subsystems will be developed, and integration of the device into the network will be outlined.
- Independent Review - During the initial stages of work package 2, an independent review of the design and technical performance of the HIT device will be completed by Cardiff University. The first stage gate will occur following the completion of the active power control transformer concept. If the review of the active power control transformer does not pass the stage gate review, then the project may proceed to phase 2 utilising the HIT device. This is dependent on a successfully independent review of the HIT device by Cardiff University and a positive initial business case for voltage control only from WP1.
- Design and modelling of device – depending on the outcome of a successful stage gate review, the active power control transformer will be designed and modelled in detail. This will include development of a mathematical model of the device, its operational states and its integration into the distribution system.
There will be 2 stage gate reviews during phase 1 to assess the efficacy of the transformer design and to review the network application. The first stage gate will occur mid-way through WP1 and WP2, when the functional requirements have been defined and initial design is complete. The second stage gate review will be completed at the end of phase when full design is complete.
Cardiff University have subject matter experts in both Power Electronic technology and Electromagnetics who will be providing an independent review of the active power control transformer and HIT technologies during both stage gate reviews.
Phase 2: Functional Requirements and Solution Development
Phase 2 will only proceed depending on successful stage gate reviews during phase 1, and may consider either the active power control transformer and/or the HIT depending on the outcomes of the stage gate reviews. This phase will involve detailed power systems analysis on typical LV networks where the solution would be effective and to also understand the impact of the solution’s implementation on other network aspects, such as fault level and power factor. The level of voltage control required to alleviate voltage constraints will also be considered in the cases where this will defer reinforcement (WP3). The extent of active power control and load sharing will be determined to inform the design and manufacturing of a benchtop prototype of the ACT. The benchtop prototype will be tested to assess its performance in relation to active power and voltage control capabilities (WP4).
This phase will involve the following work packages:
WP3 – Headroom Assessment and Cost Benefit Analysis
Work package 3 commencing is dependent on successful outcomes from the stage gate reviews.
The aim of WP3 is to assess the amount of headroom that can be achieved through utilising the smart transformer, using detailed power systems analysis of representative LV networks. This headroom will be defined as the level of thermal and/or voltage constraints that can be alleviated on the constrained feeders. The stages involved will be as follows:
- Development of PowerFactory model for smart transformer - detailed network models for Power system studies will be created using Power Factory and validated in a test network model, to demonstrate whether expected behaviour is in line with available design standards.
- Development of representative networks – full LV network models will be produced for up to 5 LV network feeders from WP1 that are forecast to benefit from the technology. Models will include representation of LV link points to enable two neighbouring feeders to be coupled, and will be developed with sufficient detail to enable modelling of the effects of LCT update, thermal, voltage and fault level constraints.
- Applying LCT uptake - the LCT uptake rates deployed during WP1 (EV, PV and heat pumps) will be deployed to each feeder model. The models will be run with the link box open and closed, and a comparison will be made to compare the differences and understand whether looped feeders offer a viable option for increasing thermal and/or voltage capacity on the network for each archetype.
- Applying smart transformers – the smart transformer(s) will be tested on a number of factors, to determine its ability to alleviate common network constraints that have been identified during the development of representative networks.
- Cost Benefit Analysis – a cost benefit analysis of deployment of a smart transformer solution will be completed using Transform, including a comparison with other BaU and Novel solutions.
WP4 – Smart Transformer Development and Testing
Depending on the outcomes of WP1 and WP2, either a prototype of the active power transformer will be manufactured and tested, or the HIT will be tested to reflect likely network scenarios.
- Design of prototype - the prototype design will be informed from WP2 findings and functionality requirements will be informed from WP3 findings.
- Prototype testing - a specialised test rig will be designed to allow benchtop testing of the prototype to be completed. This will include source and load control capabilities for primary and secondary sides for all required testable functionality.
- Design optimisation - As procured hardware becomes available, the electrical and electronic components of the device will be built and tested as sub-assemblies to identify and resolve issues, optimising the final prototype. The performance of the prototype will be fully assessed by Cardiff University as well as NGED policy engineers.
- Results and recommendations – an independent review of the results from prototype testing will be completed and recommendations will be made for future project phases.