New concept for co-ordinated power-plant control

Control schemes for boiler-turbine units have formerly given priority to the grid requirements by regulating steam extraction from the boiler with minimum delay. With boiler systems that are slow to respond, steam storage is exhausted before increased steam production begins, leading to temperature and pressure fluctuations, material stresses and shortened plant life. A system is described in which dynamic models of the fuel mills, boiler and turbine are used to delay change to the load set point of the turbine controller. This system optimises the rate of load change with stress-free operation. It has been in service in a 750 MW unit over a 2-year period.