|Funding mechanism||Network Innovation Allowance (NIA)|
|Duration||Aug 2016 - Aug 2018|
The LV Plus project aimed to tackle the challenges of increasing demand for power in residential networks that DNOs are facing. The project proposed running the single-phase LV distribution network at a voltage of 400V and using the Power Electronic Converter (PEC) to step LV supply voltage down to 230V at the customer’s connection. An earlier Technology Strategy Board (TSB) Feasibility Study suggested it would be possible to increase capacity by 62% at approximately a third of the cost of reinforcement using this method.
The project aimed to specify, design, test and build prototypes to enable a detailed site trial to be carried out to evaluate the PEC performance in normal operation. Key to the design was the use of silicon carbide (SiC) devices which are rated for high power operation. A functional specification defined the maximum, peak and continuous rating and the intended physical dimensions of the enclosure of the PEC was developed. The protection requirements for the PEC were defined so that it effectively coordinated with the miniature circuit breaker (MCB) protection within residential customers’ consumer units.
Initial prototypes used SiC devices in an AC chopper design. These failed, experiencing problems which included (a) the current measurement was especially sensitive to noise leading to instability (b) the impact of parasitic loads due to switching rates, (c) the clamp circuit long discharge times resulted in staggered increases in the voltage, (d) difficulty in controlling the circuit at low load and (e) various elements in the design which lead to repeated tripping of the circuit. Due to the failure of the initial SiC designs, the site trials were cancelled and efforts concentrated on alternative designs and topologies.
An innovative circuit design using GaN devices in smaller flat pack packages was developed. This design combined with a unique switching control sequence at 250kHz, resulted in a stable 2.5kW module operating at 350Vac input, 230Vac output and an efficiency of 98%. With further development funding, the key consortium partners estimate it is feasible for this prototype to be developed to a suitable level for full site trials within 3 years.
Analysis of stakeholder functionality requirements was carried out and this indicated that 60% of these could be met without modifying the PEC functionality. The study also concluded that within the UK the current PEC functionality is best suited to medium energy consumers. The best global opportunities to exploit the technology exist in the Western Europe and the Asia- Pacific region due to synergies in network design, size of population and the take up of Electric Vehicles (EVs).
In conclusion, the principle of reducing network capacity using PECs remains viable. The alternative GaN design shows stable performance and addressed the problems encountered with the earlier SiC designs. Further development is required for the GaN design to be used in full site trials and wider implementation.
More information about this project can be found in the LV Plus closedown report.