Stability and noise sensitivity of a digital-analogue control system for the automatic loading of a power system

The performance of an automatic control system for load dispatching is examined. The control system comprises a digital computer and analogue-control equipment for regulating the power outputs of the generating units via the turbine throttle valve. The behaviour of the control system is determined in terms of the interaction which takes place between the local analogue loops and the digital load-scheduling system. The dynamic equations of the overall control scheme are established, and the stability boundaries are derived for the case when the digital controller is slow acting compared with the analogue control loops. The sensitivity of the control scheme to metering and telecommunication noise entering the digital system, as well as the significance of the digital sampling rate, is determined.