A Microgrid is an electrical network that can be connected to the public supply network but is also capable of autonomous operation.  To be effective, a microgrid should be able to transition, without loss of supply to the consumers relying on it. Although microgrids may access different forms of generation equipment and may include control schemes that optimise either economically or environmentally, they may also act to provide supply security, resilience and quality.

Britvic Factory Microgrid

An expansion of the Britvic processes demanded a greater electrical import capacity.  The local public supply network was at its capacity limit and could not meet the higher demands of the factory without significant and longer term reinforcement.  In order for the factory to operate, it therefore needed the addition of substantial on-site generation.  The on-site generation included Combined Heat and Power (CHP)  gas engine generators to provide process heat and standby diesel generators to provide fast recovery from a loss of supply from the network or generation.  Diesel generators, due to their negative environmental impact, are regarded as a back-up only supply for resilience and failure recovery.

The Customer Challenge

To provide a Microgrid that incorporates the selected generation and:

  • provides resilience against loss of the public supply network
  • permits a preferential selection of available generation plant
  • Provides sufficient generation for operational security without exceeding the fault level infeed limitations for the public supply network

PSE 2 Solution

As the preference was to operate with gas engines in lieu of the diesel generators in both mains parallel operation and as a Microgrid, PSE 2 designed the system to incorporate the following:

  • A high impedance reactor between the public network and the generation to limit the fault level and “decouple” the impact of voltage disturbances on the public network from the factory network
  • A rotating mass inertia and motor generator units to provide voltage support to the factory system, fast load pick-up and rejection on disturbances and  to maintain the Microgrid frequency stability

PSE 2 also designed, supplied, configured, tested  and commissioned a regulatory control strategy on the customer selected control platform to enable the Microgrid to act with resilience and stability when transitioning between autonomous and parallel control.

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Microgrid schematic