ECE 576 POWER SYSTEM DYNAMICS AND STABILITY Lecture 9 Synchronous Machine Controls - Excitation Professor Pete Sauer Department of Electrical and Computer Engineering © 2000 University of Illinois Board of Trustees, All Rights Reserved

Speed and voltage control

Exciter models (to sync mach)

constant 1

use

For the self-excited dc machine, the result is:

is the output of an amplifier (error voltage amplified) This determines

Steady state

Exciter saturation example Given: Find:

Voltage regulator model Amplifier In steady state Big There is often a droop in regulation

This control can exhibit instabilities. The open-loop eigenvalue can be positive for small saturation. Add a stabilizing transformer.

Large Lt2 so It2  0

Make voltage regulator control a different voltage. Load compensation circuit Make voltage regulator control a different voltage. b. Reactive power sharing.

Example

Balance 3-phase, ABC sequence

Example 1

If the Vref = 1.0, volt. reg. will tell the exciter to lower Vt

Example 2

VR1 will lower excitation. VR2 will increase excitation. Reactive power sharing Suppose Q = 0 and VR1 will lower excitation. VR2 will increase excitation.

IEEE Type I excitation system model Vt may be uncompensated or compensated