Series cascade control of coal-fired drum boiler

Among many factors decreasing the control performance of coal-fired drum type boiler, nonlinearity is the major one. While boiler operated, the fuel flow rate affects directly the drum pressure and this in turn affects the throttle pressure. This can lead to a series cascade control structure: the output of primary controller changes the set point of drum pressure, and the output of secondary controller manipulates the coal feed rate. Simulation results show that the designed series cascade control system can improve effectively the command response of boiler while operated over a wide range.