Abstract:
Extensive field experience in micro-hydroelectric systems in remote rural communities demonstrates that
the use of a typical Automatic Voltage Regulator (AVR), as supplied with a brushless self exciting
synchronous alternator, can be the cause of unsatisfactory system performance. This paper presents
results from experiments undertaken on a full scale micro-hydroelectric test rig as well as system
modelling with PSCAD. The source of the instability is considered to stem from the similar time
constants of the ballast load frequency controller and the AVR as two competing feedback control
systems. System modelling is used to verify steady state operating points, and confirms that the under
frequency roll-off (UFRO) characteristic of the AVR also contributes to unsatisfactory performance.
