Droop Control (Load Sharing Between Generators)

A control method for sharing active power (via the speed governor) and reactive power (via the voltage regulator/AVR) between two or more generators or gensets operating in parallel on the same network, in which each generator deliberately allows its frequency (respectively voltage) to 'droop' as the power it delivers increases — typically a 3-5% frequency drop between no load and full load. Because all parallel generators follow the same relative droop characteristic, an increase in total load automatically distributes itself proportionally across all generators according to their capacity, without requiring a communication link between the governors. This contrasts with isochronous control, in which a generator attempts to keep frequency/voltage constant regardless of load — suitable for a single generator operating alone on an island network, but when used in parallel operation without additional load-sharing logic, isochronous control leads to unstable power distribution or even circulating power between the generators.