Supplemental control in a modern digital excitation system

This paper presents various supplemental control functions such as VAr or power factor control, power system stabilizers, and limiters. These are summing point type controllers and make up the outside loop of a two-loop system. The voltage regulator forms the inner loop and is implemented as a fast PID controller. Most of the outer supplemental control loops use PI controllers. The simplicity of the controllers and the ease with which they are designed/tuned makes the modern digital excitation system very attractive for varied applications. The practical issues related to various control functions are addressed. The test results indicate desirable features in the supplemental control functions.