Electricity + Control August 2016

ENERGY + ENVIROFICIENCY: CARBON TAX ENERGY + ENVIROFICIENCY I n C o n v e r s a t i o n W i t h

• Microgrids are networks of smaller independent but inter- connected generation ‘islands’. • Gas, hydro, diesel HFO, solar, wind or geothermal sources can be incorporated into the microgrid solution. • The core purpose of microgrids is to manage and combine the available power to best meet demand.

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Key features of microgrids The core purpose of ABB’s microgrid solutions is power security and grid resilience. Since no single generation option is able to offer this all of the time, it makes sense to combine power generation sources to make sure power is always available. “While seamless power changeover is not always necessary, it is now a primary part of our offering and is often essential,” Duarte suggests. “Probably the largest microgrid market is in the USA, where you would think they have no need of it. Why? Because of the increas- ing occurrence of natural disasters, which tend to take out the grid and cripple the affected community. To minimise the impact of such events, the power needs to be restored immediately and microgrids are being installed on a redundancy basis to back up the grid in high-risk areas. Typically these are large systems of between 10 to 100 MW, but there is no capacity limit since the technology involves the management and coordination of generation, not the generation itself,” he informs MechTech. A second objective is to achieve the lowest possible levelised cost of energy (LCOE) from a combination of generation sources. “Levelised cost of energy is a stream of equal payments, normalised over expected energy production, that would allow a project owner to recover all costs – including financing and an assumed return on investment over a predetermined financial life – and expressing this total as a tariff per kWh of generation,” he explains, adding, “this is generally calculated for a 20-year life.” With this information, ABB’s Microgrid Plus DCS is able to opti- mally combine available generation sources to meet prevailing load demand at the lowest possible cost.

The dc power generated from the panels is passed through a single PVS 800 630 kW ABB inverter to generate the ac supply.

“If the grid goes into a blackout state, the PV system cannot help. So if used in this way, PV solar and wind generation can never be a substitute for base-load generation because they cannot replace the loss of grid power,” he explains. ABB’s microgrids, however, are grid forming. “While they will syn- chronise to a grid if it is available, they can also provide the references for renewable and fossil energy generation to follow. PowerStore sits between the grid and all the other generation sources, so PV, diesel and wind generation will all look to the PowerStore reference in order to synchronise. “So while microgrids can be grid connected, as we see at our demonstration plant here in Longmeadow, they are also 100%

‘islandable’. Here, we have grid-connected power, PV solar generation, the battery and diesel generation all interconnected via a common ring and automatically managed by the Microgrid Plus Distributed Control System (DCS). The unique feature of ABB’s microgrid control system is that it has a distributed network of controllers allowing for redundancy, expandability and maintenance to take place without interrupting genera- tion of power. “As soon as an outage is detected, the PowerStore provides the reference for the off-grid generation. Then, when as the grid comes back on line, the PowerStore resynchronises, which will cause the off-grid generation sources to follow. The grid can then be safely brought back into the supply mix,” he adds.

An infographic outlining the key fea- tures of ABB’s microgrid installation at Longmeadow.

August ‘16 Electricity+Control

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