Wide range operation of a power unit via feedforward fuzzy control [thermal power plants]

A two-level hierarchical control scheme for wide-range operation of fossil fuel power units is presented. At the supervisory level, a fuzzy reference governor generates, according to a variable pressure operating policy, the set-point trajectories to command the unit along any load demand pattern. At the control level, a feedforward-feedback control strategy is implemented. The feedforward control path contains a set of multi-input single-output fuzzy inference systems, designed from steady-state input-output plant data. The feedback control path consists of PID controllers in a multi-loop configuration, as currently available at power units. With this strategy, the feedforward path provides most of the control signal for wide-range operation, diminishing the control effort on the PID controllers. The feedback path supplies the complementary control signal component for regulation and disturbance rejection in small neighborhoods about the commanded trajectories. Simulation results demonstrate the feasibility of the control scheme to attain cyclic load-following operation