Automated synchronisation

Synchronisation of two alternators requires precise frequency and phase measurement and speed control of the machine to be synchronised. This paper describes a microcomputer controlled system for automatic run up of a coupled flywheel and alternator via a variable speed drive, and the automatic synchronisation of the alternator to the alternator of a 55 kW wind turbine generator. The task is complicated by the varying frequency of the wind turbine alternator which is under separate control. The flywheel control system is shown. The function of the controller is to monitor safety conditions, namely speed, temperature, oil pressure, vibration and vacuum, and subject to safety criteria, to run the flywheel up at constant power to its nominal speed, then to monitor the frequencies of the two alternators and to adjust the flywheel speed to bring these together. When the frequency and phase difference and slip rate between the two alternators are within preset limits, the synchronising contactor is closed automatically. The controller continues to monitor safety conditions and also wind speed and direction and based on this information, to initiate flywheel run-up and run-down procedures