JPS5837404A - Method of controlling boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynamic compensation method for reducing the influence of transient disturbances on a control system of a boiler or the like.

In the control system of boilers, etc., the steam temperature control system (hereinafter simply referred to as the STC system) basically consists of a feedback circuit and a feedforward circuit using a load index, and may also have a dynamic compensation circuit added. be. Dynamic compensation is 0ver Firing + when load changes.
The filter is used to absorb transient disturbances caused by under-firing. Conventional dynamic compensation methods during transient disturbances include methods that use differential signals of load signals such as power generation, main steam flow rate, fuel flow rate, and air flow rate as dynamic compensation signals, and methods that use differential signals of load signals such as power generation amount, main steam flow rate, fuel flow rate, and air flow rate, and There are methods of using a difference or a ratio as a dynamic compensation signal.

However, in the case of the former method, both signals are flow rate signals and therefore contain noise.

Therefore, when these signals are differentiated and added to the STC system, it can be used for the water injection system, but it is difficult to use it for controlling the GRF damper system or burner tilt system.

In addition, in the case of the latter method, the fuel flow rate signal has noise peculiar to the flow rate signal, and there is a sudden change at the time of burner ignition (4? is large at light load), so the difference between this signal and the main steam flow rate or It is not appropriate to use the ratio as a dynamic compensation signal because it causes disturbance to other systems.

The present invention has been made in view of these points, and provides a boiler that can remove the influence of transient disturbances in the STC system of the boiler by using the output of the main steam pressure regulator as a dynamic compensation signal. This control method has been realized. Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the response of each control element to obtain the optimum response when the load changes with respect to static characteristics.

Figure (1) shows the desuperheater output temperature, Figure (b) shows the water inlet injection amount, and Figure (C) shows the GRF control damper opening degree. Both horizontal axes indicate the amount of load.

In the figure, the difference between the broken line and the solid line is the required amount of dynamic compensation. As shown in the figure, the main causes of fluctuations in the response of system 6 are 0ver firing and under firing during load fluctuations.
Firing. This 0ver Fillng or Under Fillng amount can be regarded as the difference between the load signal (usually the main steam flow rate) and the fuel flow rate.Here, attention is paid to the fuel flow rate request signal (hereinafter simply referred to as the BM double signal). FIG. 2 is an electrical connection diagram showing one embodiment of the BM signal generation circuit. In the figure, 1 is a subtracter that outputs the difference between the main steam pressure and the set pressure. 2 is a multiplier that multiplies the output of the subtracter by a certain constant K. 3 is
This is a main steam pressure regulator that integrates the difference between the main steam pressure and the set pressure.

4 is a gain compensation setting device which receives the main steam flow rate and obtains a gain compensation output. 5 is a multiplier that multiplies the output of the multiplier 2 and the output of the compensation setting device. 6 is an adder that receives the main steam pressure regulator 3, gain compensation setter 4, multiplier 5, and main steam flow rate output, and outputs the summed value thereof.

The output of the adder 6 becomes the BM multiplied signal. That is, the BM double signal is the sum of the main steam pressure controller output and the main steam flow rate. The BM outputs of and and are P-controlled outputs. Here, if we look at the output of the main steam pressure controller 3 statically, the output is approximately 50%, and even if fluctuations due to load are included, it is within 50%±2%. Therefore, the change from 50% ± 2% of this output is calculated as a transient 0ver.
It can be regarded as a Firing or Under Firing request amount, and the output of the main steam pressure controller 5 can be used as a dynamic compensation signal.

The influence of transient disturbances can be removed by introducing this dynamic compensation signal to the STC system and adding it in a direction that cancels out transient disturbances due to load fluctuations.

FIG. 3 is an electrical connection diagram showing another embodiment of the BM signal generation circuit. In the figure, 10 is a main steam pressure regulator that multiplies the difference between the main steam pressure and the set pressure by a constant and integrates it.

Reference numeral 11 denotes an adder that adds the output of the main steam pressure regulator and the main steam flow rate and outputs the result.

The output of the adder becomes the BM multiplied signal. This BM double signal PI
It has a controlled output. In the circuit shown in the figure as well, the output of the main steam pressure regulator 10 can be used as a dynamic compensation signal as in the case of FIG.

In the case of the embodiments shown in Figures 2 and 5, the output of the main steam pressure controller is approximately 50%, and if the receiver side that receives this output attempts to amplify the output, the output will become saturated due to the offset. There are cases where this happens.

In order to avoid such inconvenience, it is sufficient to subtract the offset from the output of the main steam pressure regulator and transmit only the variation to the receiving side.

As mentioned above, if the output of the main steam pressure controller is used as a dynamic compensation signal, a stable signal that is not affected by flow noise or the like can be obtained. Furthermore, since the output includes an integrated first-order lag element, stable dynamic compensation can be performed even for sudden sudden load changes.

FIGS. 4 to 6 are electrical connection diagrams showing examples of applying dynamic compensation signals to an STC system. Figure 4 shows an example of application to a control system for controlling main steam temperature, and Figure 5 shows main steam temperature III.
Figure 4 shows an example in which the IIs meter output is applied to a control system connected in cascade to a reduction output port temperature controller, and Figure 6 shows an example in which it is applied to a control system for reheating steam temperature adjustment.
20 is a main steam temperature controller that multiplies the difference between the main steam temperature and the set temperature by a constant, differentiates it, and integrates it. 21 is a gain compensation setting device which receives a load signal and obtains a gain compensation output; 022 is a main steam pressure controller 20; a gain compensation setting device 2;
This is an adder that receives the respective outputs of 1 and the dynamic compensation signal, adds them together, and outputs the result. The output of the adder is guided to a water injection control valve to adjust the opening degree of the pulp.

In FIG. 5, 30 is a main steam temperature controller that multiplies the difference between the main steam temperature and the set temperature by a constant, differentiates it, and integrates it.

31 is a gain compensation setting device that receives a load signal and obtains a gain compensation output. 32 is an adder that receives the output of the compensation setter, the main steam temperature controller 30, and the dynamic compensation signal, and outputs the sum of these signals. 33 is a desuperheater outlet temperature controller that multiplies the difference between the temperature at the desuperheater outlet and the output of the adder 32 by a constant and integrates the result. The output of the temperature controller is guided to the water injection control pulp to adjust the opening degree of the pulp.

In FIG. 6, 40 is a reheat steam temperature controller that multiplies the difference between the reheat steam temperature and the set temperature by a constant, differentiates it, and integrates it. Reference numeral 41 denotes an adder that receives the output of the controller, the dynamic compensation signal, and the output of the gain compensation setter 44, and outputs the sum of these signals. 42 is an upper limiter that receives the output of the adder and the output of the gain compensation setter 45. 43
is a lower limiter which receives the output of the upper limit and the gain compensation setter 46. These upper and lower limit limiters keep the upper and lower limit values constant so as not to apply excessive input to the operating section or the like. The output of lower limit 43 is:
The damper opening is adjusted by the GRF control drive.

As described above, in any of the cases shown in FIGS. 4 to 6, the dynamic compensation signal is added in a feedforward manner, and the influence of transient disturbances due to load fluctuations can be canceled. Note that the required amount of the dynamic compensation signal changes depending on the amount of load fluctuation. Therefore,
In some cases, the dynamic compensation signal may be obtained by multiplying the output of the main steam pressure controller by the output of the gain compensation setter.

As described above in detail, according to the present invention, the main steam pressure regulator output is used as a dynamic compensation signal,
It is possible to realize a boiler control method that can eliminate the influence of transient disturbances on the STC system of the boiler.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the response of each control element. FIGS. 2 and 5 are electrical connection diagrams showing an embodiment of the dynamic compensation signal generation circuit. 4 to 6 are diagrams showing application examples of dynamic compensation signals. 0 1... Subtractor, 2... Multiplier, 3.10... Main steam pressure controller, 4... Gain compensation setter, 5... Multiplier, 6, 11... Adder, 20.30... Main steam temperature controller, 40... Reheat steam temperature controller. Agent: Patent Attorney Makoto Ozawa (゛・nir″□・,
. 1-' Figure 2 (a) (b) (c)

Claims (1)

[Claims] When controlling steam temperature with a boiler control system that combines feedback control with dynamic compensation to absorb transient phenomena caused by disturbances, the main steam pressure controller output is used as a dynamic compensation signal. Boiler control method.