Power System Oscillations
Chapter 6: Generator Controls
Abstract
In this chapter, we will discuss some aspects of the normal generator controls, i.e., the speed governor and the automatic voltage control. It is normal for these controls to be set up more or less independently of the requirements of the generator in an interconnected system. The governor’s purpose is to control speed, and an exciter with an automatic voltage regulator is used to control generator terminal voltage. Or at least this is the stated purpose. Once a generator is synchronously interconnected with other generators, the system plays an important part in both speed and voltage control. When generators are synchronized, their steady-state electrical speeds are identical irrespective of whether they have speed governors. In such a situation, the speed governors largely control the distribution of power between generators. System operators adjust generator power by changing the reference input to the governor. Although not quite the same, the action of the automatic voltage regulators is similar. The voltages in an interconnected power system are close to their nominal values. The automatic voltage regulator essentially controls the reactive power supplied by the generator, at least until this reaches one of its limits.
