A master controller may coordinate several generating units and plant functions. Its responsibilities should be distinguished from the local controls and protective functions of individual equipment. The design should state what decisions the master makes and which functions remain available independently.
Assess shared control dependencies
Central coordination can introduce common interfaces whose availability matters to the plant. Identify the response to lost communications, unavailable units and other relevant conditions. The required behaviour should be part of the approved operating philosophy rather than assumed from a product description.
Failure philosophy
The master controller should not become an unexamined single point of failure.
Maintenance
Generator removal for planned service should ideally be understood by the plant control strategy.
Configuration control
A master controller converts multiple generators from independent machines into a managed generating plant.
Define the priority logic
The master control scheme should state how available capacity, reserve and load priorities influence generator operation. Include the intended response to a unit becoming unavailable and the conditions for admitting further loads.
Keep the plant configuration documented
Record the connected equipment, software, settings and tested operating modes. Expansion or replacement can alter the supervisory logic and should receive the appropriate review. The acceptance record should demonstrate the installed arrangement and identify any functions outside the tested scope.
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Related guidance
Engineering intent
Master Generator Controllers should be evaluated as part of the complete power system rather than as an isolated catalogue item. Operating duty, connected load, interfaces, protection, controls, installation conditions, testing requirements and lifecycle consequences determine whether the arrangement is appropriate.
Control-system requirement
The control architecture must connect sensing, source readiness, permissives, breaker or transfer commands, feedback, alarms, communications and fallback modes. An individual component test does not prove the complete operating sequence.
Engineering considerations
Individually, all four machines can start and produce power. That is the purpose of plant master control. The master controller should not unnecessarily replace the generator’s internal control functions. The local generator controller can remain responsible for appropriate: engine start sequence • engine shutdown protection • local measurements • generator status. The plant master operates above the individual machines. The generator master can form part of the PMS. Therefore it contributes no connected generation to the common bus. A generator can be mechanically healthy but selected: It may therefore be unavailable to automatic master control. This can be more valuable to the plant master than a generic:
Selection and design considerations
If all automatic generator operation now depends on that PLC: Legacy DGs can contain controllers from different generations/vendors. The modernisation architecture should identify which functions remain local and which become supervisory. A PMS should not unnecessarily take over engine-protection functions already correctly implemented in the generator controller. raise/lower contacts • analogue bias • dedicated load-share lines Likewise reactive-sharing interfaces can differ substantially between legacy and modern alternator controllers.
Integration and protection considerations
Where export is permitted, the plant can potentially regulate: Where it is prohibited, appropriate export-limiting architecture may be required. Generator master logic should integrate with that transfer architecture without duplicating it. The master controller becomes central to sustained capacity and reserve management. During complete blackout, the generator master may coordinate: Starting multiple DGs simultaneously can reduce restoration time where the system supports it. Sequential start can reduce auxiliary/control burden but increase restoration time. A master controller cannot compensate for failed local starting batteries. Multiple available generators can still depend on one common fuel system.
Testing, commissioning and verification
Intentional microgrid islanding and anti-islanding requirements must be carefully distinguished. Utility interconnection protection is not replaced by the microgrid controller. In an island with excess generation and limited BESS charging capability, renewable curtailment can become
Operating and lifecycle considerations
What happens if one 500 kW generator trips now? load, there is an immediate deficit before another generator can start. DEMAND → AVAILABLE CAPACITY → ONLINE CAPACITY → RESERVE → CONTINGENCY → SOURCE RESPONSE → LOAD PRIORITY → RECOVERY. A Power Management System coordinates electrical sources and loads so the power system operates within its approved: A PMS can be implemented through appropriate combinations of: PLC • generator controllers • dedicated power-management controllers • microgrid controls • communications • HMI/SCADA. The function matters more than the product label. Neither should independently undermine the other’s critical operating requirement.
Decision and application considerations
Generator breaker/trip feedback can identify the lost source before deeper system frequency deterioration. remains an important indicator of the island’s actual power balance. When load decreases, the master can determine whether one DG can be removed while maintaining required reserve. Where the equipment requires a cooldown sequence, the master should respect it. Do not issue an immediate normal engine stop merely because the breaker opened. Emergency shutdown remains a different function and can override ordinary master sequencing according to the equipment safety architecture. Where generators are permitted to operate in parallel with utility, the master-control problem changes. import/export • generator loading • interconnection limits • PF/reactive strategy. Do not enable utility paralleling merely because the generator controllers can synchronise.
Direct answer
A master controller may coordinate several generating units and plant functions. Its responsibilities should be distinguished from the local controls and protective functions of individual equipment.
The practical decision for Master Generator Controllers should be based on verified load, equipment, interface and site information. Where equipment-specific data, regulatory applicability or a project study is required, this guidance does not replace that verification.