Installing EV fast chargers on a constrained grid

The Ngātea Z Energy petrol station is in a high traffic area, halfway between Auckland and Tauranga, and is a prime spot for EV fast charging facilities.

Powerco supplies electricity to the Ngātea region, but the distribution grid, which spans over 10km, faces voltage constraints during peak periods limiting any potential for additional load growth, like the introduction of fast chargers for EVs.

Previously, installing fast chargers in Ngātea didn’t add up financially due to the electricity grid upgrades that would be required.

Proposal

EV charging innovators, Kwetta (formerly Red Phase Technologies), proposed installing an EV charger with a load capacity of 100kW and a flexible 400kW connection at the Z petrol station in Ngātea. While this development could greatly benefit local customers and travellers alike, it posed additional strain on the already constrained network.

The proposed EV charger load was expected to cause high-voltage (HV) constraints on the distribution feeder, leading to unacceptable voltage drops and potential electricity disruptions for existing customers.

Setting aside long-term solutions, such as installing a voltage regulator and building a new feeder line, Powerco was looking for an immediate solution to improve voltage regulation along the Ngātea feeder. This would ensure the new EV charging station could be supported without compromising the reliability and stability of the existing power supply. This required collaboration between Powerco and Kwetta to ensure that the benefits of the Kwetta innovation could be realised while maintaining a robust and reliable power network for customers.

The solution

Kwetta offered an alternative solution to correct the voltage issues by installing a Static Synchronous Compensator (STATCOM) which would regulate voltage and improve stability of the power supply. STATCOMs operate by generating or absorbing reactive power, which helps to maintain voltage levels, which is particularly important with the planned installation of an EV charger that could contribute to voltage drops. The real-time voltage correction offered by the STATCOM would ensure stable voltage levels despite the additional load.

Kwetta worked with the Powerco Planning and Innovation Team to evaluate using the STATCOM functionality to both prevent voltage disturbance during charging, and to provide 24/7 voltage correction to prevent the voltage from dropping below regulatory compliance limits.

Modelling of the grid was performed with the Kwetta EV fast charger using built-in STATCOM functionality. The modelling suggested that STATCOM functionality could both alleviate the immediate constraints and was also able to alleviate constraints to allow EV charging.

Kwetta proposed the EV fast charger included grid support functions, including STATCOM voltage support, harmonic cancelation, and Distributed Energy Resource functions to effectively unlock grid capacity.

Outcome

The Kwetta EV fast charger and STATCOM was commissioned in December 2023. After six months, data showed that the project successfully demonstrated the ability for an EV charger system to ease the voltage drop due to charging on a voltage constrained network.

The STATCOM functionality allows the EV charger to support the grid voltage during charging. Additionally, when not charging, the STATCOM supports Ngātea’s voltage during periods of high use.

The Ngātea site, which previously did not have capacity for any EV fast charging, with the Kwetta solution is now able to support up to 500 kW of EV fast charging during busy periods. The solution was able to be deployed in less than three months, much faster than planned network upgrades, and in time for the influx of summer holidaymakers travelling through the region.