Thermal power generation unit main steam temperature control method

Abstract

The invention provides a thermal power generation unit main steam temperature control method. The thermal power generation unit main steam temperature control method comprises the following steps of 1, establishing a dynamic performance relation according to the dynamic performance of a boiler; arranging a state observer in the boiler and conducting computing on a smoke baffle instruction and themain steam flow as inputs of the state observer through an algorithm in the state observer to obtain a state feedback value, transmitting the state feedback value to a control device and transmittingan opening and closing instruction to a baffle through the control device; 2, establishing a static performance relation according to the static performance of the boiler, wherein the relation is shown as the formula: G(h<s>-h<w>)=BQ<eta>; and 3, establishing a steam temperature control loop according to the dynamic performance in the step 1 and the static performance relation in the step 2, wherein the steam temperature control loop comprises coal quantity control, feedwater quantity control and attemperation water flow control. Thus, the thermal power generation unit main steam temperature control method has the advantage that the main steam temperature control effect is improved.

Description

technical field [0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a method for controlling the main air temperature of a thermal power unit. Background technique [0002] At present, the main steam temperature of the boiler refers to the steam temperature after the final superheater. AGC control refers to automatic power generation control. At present, the AGC control strategy of domestic large-scale thermal power units mainly adopts the configuration logic provided by major foreign DCS (heat scanning) manufacturers, and adopts the adjustment scheme of load command feedforward and PID feedback. The idea is: as far as possible, the entire control system is set to an open-loop adjustment method, and the feedback adjustment only plays a small adjustment role. This scheme requires that the parameters of the feedforward control loop must be set very accurately. For foreign units with stable coal types, stable unit equip...

AI Technical Summary

Problems solved by technology

[0004] (1) The ability to eliminate disturbance is poor, and it is prone to large fluctuations in parameters and adjustment oscillations; this is the most common situation in the operation of the unit at present. , the control system often has unstable control or the temperature and pressure deviate greatly from the set value, which seriously affects the operation safety

[0005] (2) The rate of unit load rise and fall is low; with the conventional AGC control scheme, due to the inability to find an effective control method for the controlled object with a large lag, the rate of increase and decrease of the unit load is only about 1% / min, and the peak regulation and frequency regulation of the unit Poor capacity, unable to meet the response requirements of the power grid to the unit load

[0006] (3) The change of coal type has a great influence on the control system; when the coal type changes, the control system lacks adaptive means, and the control performance also deteriorates accordingly

In order to ensure the safety of the unit, the operators can only operate at a very low variable load rate

[0007] (4) During normal AGC adjustment, the control quantities of fuel and water supply fluctuate greatly; during normal AGC operation of the unit, due to the frequent and repeated changes of the AGC command (every 1 to 2 minutes on average), the unit’s fuel, water supply, air supply, etc. Each control quantity also fluctuates greatly back and forth. At this time, although the controlled parameters such as main steam pressure and temperature are relatively stable, it will cause repeated changes in the thermal stress of the boiler water wall and superheater pipes, which will easily lead to the peeling off of oxide scales and greatly increase the boiler explosion. tube possibility

[0008] To sum up the above problems, the main reason is that with the change of unit working conditions and coal types, the dynamic characteristics of the controlled object of the unit have become worse and worse, the lag and inertia of the process have become larger and larger, and the object is nonlinear. In this case, it is difficult to coordinate the contradiction between the rapidity and stability of the control system by adopting the conventional AGC adjustment scheme of load command feedforward and PID feedback. , the conventional PID control can not realize the automatic control of the casting of the baffle

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