Local voltage control is key to EV charging challenge
With World EV Day on September 9th, Dr Jon Hiscock, CEO of grid voltage control specialist Fundamentals Limited explores how the UK electricity industry needs to accommodate millions of new EVs chargers without unbalancing the grid.
The growth of EVs in the UK may be stuttering, but only temporarily. Government policies, plus the availability of ever-cheaper models, mean the electricity industry will need to accommodate millions of new EV charge points in the next decade.
Figures from ZapMap indicate that in July 2024, the UK had 66,779 public chargers with 99,922 connectors. New public chargers are being added at a rate of around 2,000 per month, with a government target of 300,000 by 2030. But there are already more than 900,000 private chargers at homes and offices – double the 2022 number.
The EV hubs which are appearing on motorways and in cities with lots of high-speed chargers are not much of an issue for the grid as a whole, as they are can usually be connected directly to high voltage parts of the network via large substations. The real issues are likely to be with an explosion of home chargers impacting the distribution networks.
Millions more EV chargers?
Demand for home chargers is certainly being driven by the enormous gap in costs between topping up vehicles at home, at around 20-25p per unit, and public chargers which can cost 80p or more. It’s the difference between making EVs cheaper to fuel than fossil-powered equivalents and more expensive to run.
Even allowing for the fact that an estimated eight million UK households have nowhere suitable to fit an EV charger, that still leaves millions more who will be in the market for one. In many new housing developments, EV chargers are being fitted as standard.
The main challenge ahead is plain enough. If millions of drivers plug their vehicles into 7.2kW chargers during the peak demand period of 5.00 to 7.30pm, voltages will drop across the low voltage network unless they are controlled more dynamically than at present. Furthermore, and due to the fact that UK households are connected to a single phase of the three-phase system, phase imbalances will increase and also need to be controlled.
Bad trips
The peak demand issue is only one of a range of voltage control problems, caused by our transition from a centralised grid designed in the 1950s, to a landscape populated with an increasingly diverse array of distributed energy resources (DERs), intermittent renewables and historic changes in customer demand.
We are increasingly being asked to help network operators with over- as well as under-voltage issues. For example, customers may find their home EV chargers trip out where there is a high concentration of rooftop solar panels in the area, causing sudden voltage changes as sunshine levels fluctuate.
Problems can be particularly acute at the ends of networks, with ageing infrastructure far from primary substations, that was not designed for newly dynamic changes in supply and demand.
But fixing localised voltage problems piecemeal is only a stopgap. We need to address voltage control at a strategic level.
Total Voltage Control
Fundamentals launched the concept of Total Voltage Control at the CIGRE Paris ‘24 Conference in August as a way of focusing minds on what needs to be done in the voltage field to manage the transition of the grid from its 1950s origins to the new super-dynamic era. That includes accommodating millions of new EV vehicles and other LTCs (Low Carbon Technologies).
Our core proposition is that we need a grid-wide approach to voltage control. The centralised transformers and tapchangers that controlled voltages 70 years ago are still doing a great job. But they are no longer responsive and agile enough to cope with a low carbon grid .
We need to change our voltage control perspective from central control towards solutions which extend from primary substations into the furthest reaches of networks, at local community and street levels.
Smart AVCs (automatic voltage controllers) are increasingly becoming standard equipment in major substations, delivering highly effective voltage control over whole areas. These devices can optimise network voltages, taking account of a diverse range of LCT connections, but there will be parts of the network which will require local support which is an important aspect of Total Voltage Control.
Smart automatic voltage controllers enable substations to respond immediately to sudden changes in supply and demand – including from EV chargers.
Local issues, local solutions
One of the most promising technologies for grid support ‘at the edge’ (local community and consumer parts of LV networks) can solve multiple problems associated with an increasingly dynamic grid. Power electronics-based devices can provide voltage regulation capability for LV networks whilst simultaneously shifting real and reactive power between phases to reduce or even remove imbalances. These devices can be installed on overhead (pole-mounted) and underground (ground-mounted) networks. Further grid support capability can be provided by integrating the devices with battery storage units and allow owners to participate in flexibility markets..
Like the AVCs higher up the network, these new technologies can be connected to operators’ management system to deliver grid-wide voltage control at unprecedented levels.
Community-sized batteries like this one in Australia can help balance local networks when multiple EV chargers are plugged in.
The power of data
In addition to rolling out smarter and more connected hardware solutions, operators are increasingly deploying new ways to measure and predict how customers use electricity.
For example, data from smart meters is being used to optimise voltages, in a project on which we are working with Northern Powergrid. This alone could shave more than £20 off average bills and cut carbon emissions by up to two million tonnes a year, if applied nationally: the equivalent of removing 200,000 cars from the road
Artificial intelligence is also being used to analyse and model when, where and for how long EVs are plugged in, down to street level, so suppliers can predict and react to demand.
Changing customer behaviour
The electricity industry has much to do to ensure that millions of new EV chargers can be added to the grid, while balancing supply and demand, and ensuring that voltages remain stable. But so do EV owners and their suppliers.
The most obvious solution is for customers to sign up for smart tariffs, so they can charge their vehicles outside peak times, when electricity is both cheaper and greener. That will require suppliers to make such tariffs easier to use.
The second answer is to make public chargers more plentiful and priced in line with domestic tariffs.
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