Energy balance-based control method of main steam pressure of supercritical CFB (circulating fluidized bed) boiler

Abstract

An energy balance-based control method of main steam pressure of a supercritical CFB (circulating fluidized bed) boiler includes the steps: S1, after a main steam pressure deviation signal P<T>-P<TS> of a unit is regulated by a PID (proportion integration differentiation) regulator, a signal A is output; S2: a steam turbine demanded heat signal is acquired through a steam turbine energy demand model; S3, a heat signal provided by boiler energy is acquired through an instant carbon mechanism model; S4, subtracting the steam turbine demanded heat signal E<R> by the heat signal E provided by boiler energy is performed, regulating is performed with the PID regulator, and a signal C is output; S5, after subjected to time differentiation, the steam turbine demanded heat signal E<R> is multiplied by a proportional gain k so as to obtain an output signal B, and a sum of the signals B, A and C is output to a boiler master controller; S6, coal feed is regulated according to master control output of a boiler so as to control the main steam pressure. The method has the advantages that regulating quality of the unit can be improved, stability of a main steam pressure control system of the supercritical CFB boiler is improved and ability to respond to load response of the unit is satisfied.

Description

technical field [0001] The invention relates to a method for controlling the main steam pressure of a supercritical CFB boiler based on energy balance, and belongs to the technical field of boiler main steam pressure control. Background technique [0002] With the continuous increase of large-capacity units and the increasing automation of power grid dispatching, large-capacity units are required to operate in Automatic Generation Control (AGC) mode, which puts forward new requirements for the coordinated control system of power plant units. For the generator set, it is hoped that the controlled parameters will not fluctuate greatly to ensure the safe operation of the unit, that is, the stability should be given priority; for the power grid, in order to maintain the quality of the power supply system and overcome the impact of load changes on the power grid, The rapidity of unit load response should be prioritized. In order to meet the requirements of the power grid, Circul...

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Problems solved by technology

This is the main reason that affects the instability of the main steam pressure of the unit and the slow response rate of the load

[0005] (2) When the unit is operating in the sliding pressure stage, the unit must increase the pressure when the load is increased, which is not conducive to the use of boiler heat storage and affects the rate of load increase; when the unit is operating in the constant pressure operation mode, the load change process Since it does not involve the change of boiler heat storage, the load response rate of the unit is slower than that of sliding pressure operation

[0006] (3) After the CFB unit is put into AGC, it often occurs that the main steam pressure fluctuates too much in the process of loading and unloading, and the situation of quitting AGC and coordinated control

Boiler operation generally uses conventional coal feed control based on the deviation between the actual main steam pressure and the set main steam pressure, because the lag time of the main steam pressure information is too long, it is often difficult to obtain satisfactory control quality

When the main steam pressure drops to 95% of the set value, the steam consumption of the steam turbine of the unit will increase by about 1%. Large fluctuations in steam enthalpy and temperature affect the quality of steam sent to the turbine

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