Dynamic optimisation of a multimachine power system

Discrete control of a multimachine power system, containing interconnected boiler-turboalternator models, is developed using a state-variable representation. The boiler equations are associated with a conventional drum-type boiler, represented by lumped energy-storage elements, and the turboalternator models include the effects of reheater and steam-valve chest storage, with the machine formulation based on a linearised form of Park´s equations. The machines are interconnected with a transmission network, and must operate in accordance with the terminal constraints imposed by the network structure. A 3-machine system supplying induction-motor-type loads is investigated and operated using an assumed centralised computer for producing discrete integrated control of individual alternator-field excitation and turbine-governor valves. Overall control of the individual boiler units is also included, and operated in conjunction with control of the power-system units. Integral action, related to measurement of selected variables, is contained with the control formulation, and optimal control sequences are generated, using an iterative solution of the single-point boundary problem associated with quadratic loss functions. The results illustrate the feasibility of integrating all controls for the multimachine system and also the possibility of including a dynamic operating criterion, related to system line losses, for obtaining an economically optimal load distribution in the transient state.