Basic Elements of a Digital Controller for a Steam-Turbine Driven Generator

The block diagram below illustrates the basic elements of a minicomputer system for speed and voltage control as well as data acquisition of a steam-turbine driven generator unit.

Typical output variables of the generator are speed, rotor angle, terminal voltage, field (excitation) current, armature current, and real & reactive power. A number of output variables are measured by digital transducers, whose outputs are then digitally multiplexed and sent back to the minicomputer.

Related: Digital PID Controllers

Some other output variables may be measured by analog transducers, whose outputs are processed through an analog multiplexer which performs a time-driven multiplexing operation. The output of the analog multiplexer is connected to a sample and hold device, which samples the output of the multiplexer at a fixed time interval and then holds the signal level at its output until the A/D converter performs the analog to digital conversion. Therefore, following the multiplexer, time sharing is done amongst a number of signal channels.

You can also read: Basic Features of Modern PID Controllers