SYNC

Solar Yield Network Constraints

Project background

WPD has connected significant amounts of embedded generation to its distribution network in recent years. This includes a large variety of different technologies, dominated at first by wind and more recently by solar PV. 

With so much generation already connected, and significant quantities in the pipeline, most of the latent capacity within the network has now been utilised. As such WPD is looking at ways of releasing extra capacity in the most economically efficient manner. Alongside the use of traditional reinforcement, the roll out of alternative connections has been one of innovative manners this has been done, building on the flexibility of generators. These give the option of trading off capital expenditure and time delays against potential curtailment. This moves from a passively operated network to a more active one. 

Whilst the inherent flexibility of generation is now being used, the flexibility of the demand side is as yet untapped. 

As part of the SYNC project we looked to test a range of Demand Side Response (DSR) techniques to help address many of the different challenges being posed by PV generation. By engaging with industrial and commercial (I&C) customers we could release additional capacity or even improve power quality. 

There are 4 techniques that project SYNC looked to investigate: 
(T1) - Automated demand increase / generation limiting in line with variation in solar yields. 
(T2) - Directly matching flexible load with flexible generation 
(T3) - Manually dispatched response signals from a WPD control facility (DSR) 
(T4) - Creation of suitable ToU (Time of Use) tariffs to encourage appropriate demand 

The project required significant engagement and involvement of third parties including demand customers, generators, storage operators and National Grid. WPD built on the learning gained in the FALCON project and directly manage a full service program directly. By doing so we attempted to demonstrate how to maximize value to the industry and minimize the cost to customers.

Scope and objectives

As with other DR projects the scope can be limited by the necessity to gain the support and engage with customer’s willingness to participate. WPD will however identify suitable areas in the South West franchise area, where there are current issues arising from high penetration levels of solar generation coupled with insufficient load at times of high yield. 

The trial will be limited to half hourly metered supplies. Particular focus will be centred on large energy users who are expected to have greater volumes of potentially beneficial latency within their processes as well as a comprehensive presence across the affected areas. 

Initial work will be required to develop an attractive proposition that will be acceptable to I&C site operators to vary their electrical load so that it is more compatible with peak output from embedded renewables on the same 33kV feeders. It is expected that public engagement will be primarily direct to customers but aggregator routes will also be investigated to verify if they can meet the trial service requirements. The various methods will be applied over a two year trial period to establish the most effective when measured against the key criteria: 

• Cost of operation 
• Reliability / effectiveness 
• Ease of participant recruitment 
• Ease of ongoing operation. 

The objectives of the trial were to validate the following:

Success criteria

• Method(s)

  The work carried out was split into 4 techniques:

  Technique 1: Impacts of cloud cover on PV dominated networks

  Alongside the steady state impacts of connecting PV on the network, there is a potential for high concentrations of PV generation to cause more dynamic issues. With generators drawing power from the same source there is the option for multiple generators to act in concert with changes in cloud cover. This could cause issues with voltage stability potentially increasing the use and wear on transformer tap changers. Whilst this has been highlighted anecdotally, WPD has had no evidence of such issues occurring on its network.
  
  The initial T1 investigations focussed on the existence of any rapid changes on the network and any potential implications.

  Technique 2: Load Matching

  In T2 WPD sought to investigate the possibility of utilised in increases in demand to provide a direct benefit to customers through a reduction in curtailment. By matching additional demand to generation curtailed under an ANM system, curtailment could be reduced and value created for the demand. The aim of T2 was to investigate the feasibility of creating a market between demand and generation customers in such a market.

  Technique 3: DSR Turn-Up

  In T3 we sought to build a DSR service to help WPD manage network constraints during times of low demand and high generation. This aimed to build on the findings from project Falcon and deliver a similar DSR service in reverse.

  Technique 4: DUoS Adjustments

  T4 involved a desktop study into the effect of modifications in charging arrangements on summer demand.

• Lessons learnt

  Technique 1:

  • The initial investigation into rapid fluctuations in voltage due to PV has uncovered no major issues. Whilst it is certainly true that cloud cover does create large changes in real and reactive current, the voltages observed remain within limits for the substations monitored. 
  • In general the literature agrees with this observation. There are no examples of major issues, with most concerns raised from very conservative modelling. 

  Technique 2:

  • There is currently little requirement for a load matching scheme due to low levels of ANM curtailment. 
  • In addition implementing such a scheme has high risks of causing detriment to other customers limiting the potential for application.

  Technique 3:

  • There is value at both SO and DNO level for turn up services. 
  • There requirement do not overlap heavily, with DNO requirements focussed in the day and SO operations more active overnight.
  • Coordination between parties is possible and can be effective. 
  • Call reliability can be high, although the availability in the right areas for DNOs is limited. 
  • Customers like the flexible service, although internal approval can be time consuming.
  • Limitations for entry include the value available as well as the locational requirements and forecasting requirements.
  • Services require time to develop market understanding and confidence.

  Technique 4:

  • External interest in the topic is high and can move very quickly. This was reflected in the reduction of the T4 scope. 
• Planned implementation

  Technique 1:

  No concerns were raised and so there is no requirement for any follow up action.

  Technique 2:

  There is currently limited ANM curtailment, limiting the requirement for load matching. There are also potential risks with customer detriment. There is no planned implementation of T2. However, WPD is progressing with other commercial innovation in projects like the Plugs and Socket, where a local energy market is being investigated, and the investigation into Virtual Private wires. These projects seek to investigate alternative options to make the most of local flexibility.

  Technique 3:

  WPD is maintaining a watching brief with the National Grid DTU programme. Should volume grow in the correct areas implementation will be considered.

  Technique 4:

  Investigations will feed into existing industry processes (TSO-DSO project and TCR).

• Documents and links

  Registration form

  Technique 1 Results

  Technique 2 Report

  Technique 3 Outline

  Technique 4 Discussion Paper

  Demand Turn Up
  
  Closedown Report - Superseded
  
  Closedown Report
  
  Closedown Video

• Monthly updates

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