Exciter Models

One of the problems with the modeling of exciter and governor systems is the large time constant associated with them.  The user should ensure that the system is started and is as close to steady state as possible (unless, of course, simulation of start-up transients is required) by properly setting the machine initial conditions.  It is also possible to bypass the large exciter transfer function time constants during initialization.

Exciters are represented in PSCAD as dynamic transfer functions, and can be interfaced directly to the synchronous machine. There are several pre-defined exciters available in the PSCAD Master Library.  If none of these suit your needs, equivalent exciter systems can be constructed by using combinations of the basic control 'building blocks' from the CSMF (Continuous System Modeling Functions) section of the PSCAD Master Library.

The available exciter models are grouped into three main types:

• DC Excitation Systems:  Utilize a direct current generator with a commutator as the source of excitation system power.

• AC Excitation Systems:  Use an alternator and either stationary or rotating rectifiers to produce the direct current needed for the synchronous machine field

• Static Excitation Systems:  Excitation power is supplied through transformers or auxiliary generator windings and rectifiers.

For further details on background theory for these exciter models, see PSCAD references [4] and [5].