Cayman Islands CUC Flex 500 Upgrade
This application is on one of the islands in the Caribbean and is the main power producer on the island. Unlike the USA the Islands are unique in that they are reliant on their own abilities to source power with no opportunity to import power from another neighboring power company or country. Typically, the generators are all run in droop with the island frequency maintained manually by the operators as the island load varies during the day. During normal load transients this was not a problem however during a fault condition either on the transmission side or with the engines there was always a risk of partial or full blackouts.
TYPE OF PLANT
- Power Generation
- Engine room 4:
(2x) Caterpillar MAK8M601C 9,34MW
Engine room 5:
(2x) MAN 48/60A 12.25MW
(1x) MAN 48/60A(new) 12.25MW
(2x) MAN 48/60B 16MW
Engine room 6:
(2x) MAN 18V 48/60B 18MW
- Woodward Flex 500 Custom speed control
- Woodward Toolkit, Service tool
GCS proposed to upgrade the system with modern controls that would automatically react to fault conditions more quickly maintaining the bus frequency and keep power to the island inhabitants. GCS designed in the Woodward Flex500 which is a custom control with a more powerful processor and extensive communication possibilities which were needed to exchange data between the engines.
The control system still has the capability to run in droop as before, but now there are included additional features to improve the system. The focus was in three main areas:
GCS took the proven concept of isochronous load sharing and implemented it through the ethernet connections between the controls. The machines running in isochronous will automatically maintain the frequency of bus and share the load with the other engines also in isochronous.
The advantage of this is that the operator does not need to focus on maintaining the frequency of the bus during transients but more so on operating the remaining droop machines at their more efficient load points, typically 80%. Additionally, during a fault condition, the isochronous machines will react faster than could be done manually, to shed or take on load keeping the system away from blackouts.
Of course, if enough load is dropped on to the isochronous machines they will eventually reach an overload point and the bus frequency will start to drop. To quickly assist the isochronous machines a Droop frequency compensation function was added that will force the droop machines to start to take on load. This will happen to all droop machines at the same time improving the response time to recovery and not requiring any intervention by the operators.
When a generator trips offline due to a fault condition all of its load has to be taken up by the isochronous machines. To anticipate this load GCS implemented a load acceptance anticipation/ feedforward function that will detect when another engines breaker has opened and start to put more fuel on to the other engines before the load is seen by the controls. This significantly improved the recovery time and reduced the bus frequency swing during these events.
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