Adding renewables to the network affects the load on the grid causing more intermittent loads, heavier loads or even reverse power flows. This causes problems such as:
- Overvoltage: when the voltage is higher than required for equipment to operate most effectively. This causes a reduction in equipment lifetime and increases energy consumption with no improvement in performance;
- Undervoltage: when the voltage is lower than required for equipment to operate most effectively. This may lead to premature equipment failure, failure to start and increased temperature. Both over and under voltage conditions in the extreme can result in disconnection of the local power generating devices themselves from the grid, exaggerating the issues further;
- Poor power factor: power factor measures how effectively the current is converted into useful work output. A low power factor means that the electricity supplier effectively supplies more energy than a consumer’s bill indicates, and suppliers are allowed to charge for low power factors to compensate for the difference;
- Harmonic distortion: harmonics are current, and voltage waveforms at multiples of the fundamental frequency of the mains supply (50 Hz or 60 Hz). If the harmonic content becomes too high, it can result in damage to equipment and a reduction in efficiency;
- Phase imbalance: this is the unequal allocation of loads on the three phases of power.
Ultimately, all of these can cause issues for customers, such as damage to equipment, higher cost of bills and potentially power cuts. It could also lead to the electricity operators (distribution network operators – DNOs) breaching statutory license obligations - which detail the required maximum and minimum voltage along with the maximum harmonic content.
Also, with an aging network, there is a limit to what can be done by electricity operators to mitigate these issues. The traditional approach would be to re-build portions of the network to cope with the changes in load.
But ‘Smart’ methods could provide an alternative and more effective answer to reduce the expense and carbon footprint, sparing the millions of pounds it could cost to rebuild the network infrastructure.
One approach - Gendrive technology
GenDrive, through its experience in power electronics in the generation sector, claims to have designed a system that addresses the challenges above.
The device consists of a power electronic converter (PEC) and small transformer. It is placed on a low voltage (LV) feeder and, says GenDrive, can control the balance of power flow in each of the three phases along with other aspects of the power flow. This enables a wide window of control over voltage, current, total harmonic distortion, power factor and phase balancing.
Due to its design, the system is able to automatically correct power imbalances and maintain the parameters set down by the DNO with impressively low losses. Importantly, it can be installed at one location to control a whole LV feeder, meaning reduced customer inconvenience and increased service levels.
The GenDrive device was developed with the assistance of the UK's Energy Innovation Centre (EIC), which created a consortium of Distribution Network Operators (DNO)s to fund and assist with the development of the GenDrive device. This collaboration gave GenDrive access to the right people in the DNOs to allow their ideas to flourish. Scottish Power Energy Networks (SPEN) was the first to come on board with the project and has been active with it from a very early stage. Soon after SPEN signed on to the project, all four of the other DNOs (Electricity North West, Northern Powergrid, SSE Power Distribution and UK Power Networks) joined the project and offered funding.
“The Energy Innovation Centre was instrumental in putting together a business case for us to secure investment from the Innovation Funding Incentive (IFI) scheme,” said Nigel Jakeman, managing director of GenDrive. “Having the right contacts and really understanding what the electricity distribution networks need means EIC ... helped us get our idea in front of the right people.
“This is a two year project, which will be trialled at a demo station and will then form a real part of the grid at a research centre.
“We believe our product will address one of the major issues restricting the take up of small scale renewables and have a big impact on the way energy is produced and transferred in the future".
“GenDrive’s smart inverter clearly stood out as a valuable and credible technology with real potential to utilise the energy of renewable installations,” said Denise Massey, managing director of the Energy Innovation Centre. “We helped GenDrive to raise funding from the £36 million on offer from Ofgem’s Innovation Stimulus programme and offered them industry advice and expertise.
“Teaming up with the Energy Innovation Centre has allowed GenDrive to form strong relationships with the country’s leading electricity operators and helped them to enter new markets, gaining credibility for their product along the way. Through making these key contacts, GenDrive is closer than ever to attaining a real field test to ultimately progress their product for potential use in the market".
About the author: Martin Queen works with the Energy Innovation Centre as an Innovation Engineer. The Energy Innovation Centre (EIC) brings industry and innovation together to drive the discovery, development and deployment of new technologies and ideas that can enable the power networks to improve network efficiency, solve a problem, or help them prepare for an affordable low carbon energy future.