Plant unit master control for fossil fired boiler implemented with a digital computer

A system for controlling the operation of a fossil fired boiler-steam turbine plant, said system comprising:

• (a) boiler control means responsive to an electrical representation of load demand reference for operating the fossil fired boiler to meet the load demand reference;
• (b) an electrohydraulic control system for operating the turbine valves to direct steam from the fossil fired boiler to the turbine;
• (c) turbine control means responsive to the electrical representation of the load demand reference for controlling the operation of said electrohydraulic control system to direct steam into the turbine so that the turbine meets the plant load reference;
• (d) coordinated control means for providing the electrical representation of load demand reference in parallel to said turbine control means and to said boiler control means whereby coordinated control of the fossil fired boiler and steam turbine is achieved;
• (e) means for generating electrical representations of throttle pressure and generated power;
• and
• (f) said coordinated control means including first and second, distinct control loops responsive to the representations of throttle pressure and generated power, respectively, and each including an integrating controller responsive to the difference between its one representation and a corresponding reference value to modify the load demand reference applied to said boiler control means, and a third control loop including an integrating controller, responsive to the difference between the representation of throttle pressure and a throttle pressure reference for modifying the load demand reference applied to said turbine control means, said integrating controllers capable of processing its input difference signal with varying constants dependent upon the system mode of operation.