LVDC: Maximum Power, Minimum Losses
Ensto pioneers the world’s first LVDC commercial network.
It’s an AC (alternating current) world. Google LVDC (Low Voltage Direct Current) and you won’t find much. You may discover an LVDC network operating at an experimental level but not in commercial use. Until now.
“LVDC power distribution systems may be a potential means of implementing electricity for the future,” says Sami Laitinen, Product Manager on Ensto’s tenperson LVDC development team.
An LVDC pilot
Ensto’s pilot LVDC network is hosted by the electricity distribution company Elenia and located near Tampere, Finland. It is comprised of a 100-kVA feeder station and four substations. The pilot project concerns eight households, but future LVDC networks will of course serve many more.
Technically speaking, the LVDC branch of a distribution network creates a micro grid enabling on-grid and offgrid operation and acts as a virtual power plant towards the grid, giving voltage support with reactive power control and frequency support if there are energy shortages or production connected to LVDC. A feeder station connects to the 20kV MV grid through a transformer, rectifies the power to +-750V DC, and distributes the power via LVDC close to the customer where it is inverted back to AC-voltage by an LVDC substation. It can be set to control reactive power to compensate another area of the MV (medium voltage) grid. As a result, power losses are reduced and distribution efficiency increased.
The benefits of DC are immense. The distribution capacity increases by a factor of 10. Cables may be 10 times longer than with AC. Flickering and voltage dips disappear.
LVDC: the new standard?
The basic technology of LVDC in power electronics has been around for years in industrial applications. It is considered a basic building block for solutions such as electrical distribution in the countryside, photovoltaic (PV) control, and local energy storage. Jussi Vanhanen, Ensto’s Director of LVDC, says Ensto got involved with the technology after conducting analyses of PV solar energy storage. “After doing our own work, we then collaborated with three Finnish technical universities and began power electronics development for LVDC.”
Megatrends all support the use of LVDC. Worldwide consumption of electricity is increasing. Existing grids are falling behind the needs of customers. Renewable energy production is at the consumer level – in the United Kingdom, Ikea is selling a turnkey solar power solution. Governmental regulations demand better quality power, requiring outages and fluctuations to become relics of the past. LVDC is a solution for the most relevant problems like lack of capacity, power loss, poor quality of electricity, imbalances and variations of voltage or frequency.
Jussi Vanhanen is careful to point out that LVDC holds far more potential than just distribution. “LVDC is a way to enable energy storage, which Ensto will also pursue. And we will also offer preventative maintenance services via the utility cloud that we’re developing.” Vanhanen says the world will move more toward DC in power generation, energy storage, and consumer loads (streetlights are LED, for example). “DC is a very powerful technology for low-voltage areas, but in higher-level places AC still makes sense. But definitely look for DC to gain popularity.”
In 2018, Ensto's LVDC pilot in Finland will come fully on line. At the same time, Ensto is looking for more pilot locations in Finland as well as other Ensto countries. While it may not replace AC, it’s clearly a technology with huge implications for both society and Ensto.
Text: Scott Diel