Direct Current – Power flows in megawatt-scale Energy grids

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Research unit

SERI

Project number

24.00118

Project title

Direct Current – Power flows in megawatt-scale Energy grids

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Abstract (English)	The current electric energy distribution grid—based mainly on alternating current (AC)—has served us for over a century. Transporting energy generated at large power stations over long distances to a distributed network of consumers. It is starting to show its shortcomings due to a rise in local generation with renewable energy sources and the essentially direct current (DC) nature of many modern electric loads. Modern grids need to deal with two-way energy flows, local intermittent generation from renewables and local energy storage in stationary batteries. Medium voltage distribution microgrids using DC instead of AC hold the promise to address the shortcomings of the AC main grid. There are several initiatives in low voltage secondary distribution grids, and DC-POWER is expanding their concepts into the medium voltage range. We propose the D 3 Bus, a bipolar DC bus operating at ±1.5 kV. Compared to standard 3- phase 400V AC distribution the D 3 Bus can reduce distribution energy losses by over 90%, reduce downtime, equipment cost, and space requirements while increasing sustainability. DC-POWER demonstrates, tests and validates the D 3 Bus concept in two operational pilots: One powering an industrial-scale hydrogen electrolyser stack at 2 MW power, and one powering a new data centre with up to 500 kW installed IT power. Both pilots include sizeable solar PV arrays (200 kW), while the data centre also includes a directly coupled DC UPS solution. In order to realise these pilots, DC-POWER develops several DC-DC converters, an AC active frontend, as well as system protection components and a power/energy management system. The D 3 Bus is intended as a first stepping-stone towards standardization of MVDC distribution microgrids. It is such industry-wide standards that will enable and accelerate the adaptation of the electricity distribution system towards the energy demands of the future and net zero.

Category

Text

Abstract
(English)

The current electric energy distribution grid—based mainly on alternating current (AC)—has served us for over a century. Transporting energy generated at large power stations over long distances to a distributed network of consumers. It is starting to show its shortcomings due to a rise in local generation with renewable energy sources and the essentially direct current (DC) nature of many modern electric loads. Modern grids need to deal with two-way energy flows, local intermittent generation from renewables and local energy storage in stationary batteries. Medium voltage distribution microgrids using DC instead of AC hold the promise to address the shortcomings of the AC main grid. There are several initiatives in low voltage secondary distribution grids, and DC-POWER is expanding their concepts into the medium voltage range. We propose the D 3 Bus, a bipolar DC bus operating at ±1.5 kV. Compared to standard 3- phase 400V AC distribution the D 3 Bus can reduce distribution energy losses by over 90%, reduce downtime, equipment cost, and space requirements while increasing sustainability. DC-POWER demonstrates, tests and validates the D 3 Bus concept in two operational pilots: One powering an industrial-scale hydrogen electrolyser stack at 2 MW power, and one powering a new data centre with up to 500 kW installed IT power. Both pilots include sizeable solar PV arrays (200 kW), while the data centre also includes a directly coupled DC UPS solution. In order to realise these pilots, DC-POWER develops several DC-DC converters, an AC active frontend, as well as system protection components and a power/energy management system. The D 3 Bus is intended as a first stepping-stone towards standardization of MVDC distribution microgrids. It is such industry-wide standards that will enable and accelerate the adaptation of the electricity distribution system towards the energy demands of the future and net zero.