Computerised linear control of a.c. generator power output

The paper describes an online control system for regulating the power generation of an alternator that is connected to the supply Grid. The voltage, current and power factor of the a.c. generator are sampled and fed to the computer via analogue-digital convertors. The limits of the range of frequencies for sampling the input parameters to the computer are investigated, and an expression for the transfer function of the a.c. generator is derived. The input parameters are processed to produce the power, power angle and torque of the a.c. generator. The correcting signal from the computer is fed to the control field of a d.c. servomotor via a digital-analogue convertor. The servomotor in turn regulates the throttle opening of the petrol engine, which drives the a.c. generator. The piecewise linear method is used to approximate the relationship between the output of the a.c. generator and the throttle opening of the engine, and the technique of dynamic programming is used to optimise the overall system. Satisfactory results are obtained on an experimental system which regulates the output and stability of a 5 kVA petrol-engine/a.c. generator set.