A coordinated control method to prevent main steam overpressure in thermal power units

Abstract

The invention discloses a coordinated control method for preventing main steam overpressure of a thermal power unit, and belongs to the field of thermal control automation technology of thermal power units. The existing coordinated control system technology adds a main steam pressure large deviation compensation instruction (pressure pull-back loop) in the steam turbine main control instruction. Although the instruction can maintain the main steam pressure stable, it also greatly sacrifices the accuracy and speed of power generation. With the strengthening of the assessment of the AGC (automatic generation control) of the power plant by the power grid dispatching center, the coordinated control system has higher and higher requirements for the accuracy and speed control of power generation. Therefore, this method is no longer suitable for the current AGC regulation needs. The solution of the invention is that the thermal power unit does not work when it is running at medium and low loads, and only works when the unit is under high load and the main steam pressure is high, which can prevent the main steam pressure of the boiler from overpressure, thereby ensuring the regulation quality of the power generation, improving the AGC regulation accuracy, and effectively protecting the safety of the boiler.

Description

Technical Field

[0001] The invention relates to the technical field of thermal control automation of thermal power units, in particular to a coordinated control method for preventing main steam overpressure of a thermal power unit. Background Art

[0002] The coordinated control system treats the power plant generator set as a multivariable control object with dual inputs and dual outputs. The two inputs are: turbine control valve opening command and boiler fuel quantity command. The two outputs are: main steam pressure and actual power of the unit. The coordinated control system (CCS) is divided into boiler master control (BF) and turbine master control (TF). The boiler master control (BF) mainly controls the main steam pressure by the fuel quantity, and also affects the power generation load; the turbine master control (TF) controls the power generation by the turbine control valve opening, and also has a direct impact on the main steam pressure.

[0003] In the coordinated control system (CCS), in order to prevent the main steam pressure fluctuation from endangering the boiler safety, the original technology is to add a main steam pressure deviation compensation instruction (pressure pull-back loop) in the turbine master control (TF) instruction. Although this instruction can maintain the main steam pressure stable, it also greatly sacrifices the accuracy and speed of power generation. With the strengthening of the power grid dispatching center's assessment of power plant AGC (automatic generation control), the coordinated control system has higher and higher requirements for the accuracy and speed control of power generation. Therefore, this method is no longer suitable for the current AGC regulation needs. Therefore, a compensation instruction is redesigned, which does not work when the unit is under medium and low load, and works when the unit is under high load and the main steam pressure is high. This can not only ensure the regulation quality of power generation, but also effectively protect the safety of the boiler. For this reason, a coordinated control method for preventing main steam overpressure of thermal power units is proposed to solve the above problems, which can not only ensure the regulation quality of power generation, but also effectively protect the safety of the boiler. Summary of the invention

[0004] The object of the present invention is to provide a coordinated control method for preventing main steam overpressure of a thermal power unit, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a coordinated control method for preventing main steam overpressure of a thermal power unit, comprising the following steps:

[0006] S1. Take the derivative of the measured main steam pressure signal, the value obtained is the rate of change of the main steam pressure, and multiply it by a constant C to obtain the predicted value of the main steam pressure, and obtain the value "a";

[0007] S2, instruction "a" and main steam pressure are summed to obtain instruction "b";

[0008] S3, instruction "b" is converted into generator power correction instruction "c" through broken line function f(X), and then superimposed on the turbine master (TM) power instruction to form power generation instruction "d". The broken line function f(X) takes the main steam pressure as input and outputs the power instruction. When the input main steam pressure prediction value is lower than the rated main steam pressure of the generator set, the output is 0. When it is higher than the rated pressure, the output power instruction feedforward becomes larger. When the pressure reaches a certain value, the slope is increased to make the output increase faster.

[0009] S4. The superimposed instruction "d" acts on the steam turbine main control. The steam turbine main control is adjusted by the regulator, the output instruction increases, and the turbine regulating door is opened, thereby increasing the actual power of the unit and reducing the main steam pressure.

[0010] Preferably, when the main steam pressure does not exceed the limit, the speed and accuracy of the load regulation will not be affected, thus avoiding the influence of the previous pressure pull-back loop on the load regulation.

[0011] Preferably, the pressure pull-back loop uses the main steam pressure instruction in the coordinated control system CCS and the actual main steam pressure deviation to correct the power generation instruction.

[0012] Preferably, in S1, the constant C can be set during application. The stronger the heat storage capacity of the boiler and the greater the inertia of the main steam pressure control object, the greater the C value.

[0013] Preferably, in said S1, in order to constrain the magnitude of the effect of the predicted value, the obtained value is bidirectionally limited.

[0014] Compared with the prior art, the beneficial effects of the present invention are: it does not work when the thermal power generating unit is running at medium and low loads, and only works when the unit is under high load and the main steam pressure is high, which can prevent the boiler main steam pressure from overpressure, thereby ensuring the regulation quality of the power generation and improving the AGC regulation accuracy, and effectively protecting the safety of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the control object block diagram of the unit coordinated control system;

[0016] Figure 2 To protect the command and control logic diagram;

[0017] Figure 3 It is a schematic diagram of the broken line function f(X);

[0018] Figure 4 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1-Figure 4 , the present invention provides a technical solution:

[0021] Example 1

[0022] A coordinated control method for preventing main steam overpressure of a thermal power unit comprises the following steps:

[0023] like Figure 1 As shown in the figure, the coordinated control system controls a multivariable strongly coupled system; the two input quantities are: turbine regulating valve opening command Ut, boiler fuel quantity command Ub; the two output quantities are: main steam pressure Pt and unit actual power Ne; the coordinated control system (CCS) is divided into boiler master control (BF) and turbine master control (TF), BF mainly controls the main steam pressure by the fuel quantity, and also affects the power generation load; TF controls the power generation by the turbine regulating valve opening, and also has a direct impact on the main steam pressure.

[0024] like Figure 2 and Figure 4 As shown, S1, take the derivative of the measured main steam pressure signal, the obtained value is the rate of change of the main steam pressure, and multiply it by a constant C to obtain the predicted value of the main steam pressure, and obtain the value "a";

[0025] S2, instruction "a" and main steam pressure are summed to obtain instruction "b";

[0026] S3, instruction "b" is converted into generator power correction instruction "c" through broken line function f(X), and superimposed on the turbine master (TM) power instruction to form power generation instruction "d". The broken line function f(X) takes main steam pressure as input and outputs power instruction, such as Figure 3 As shown in the figure, when the input main steam pressure prediction value is lower than the rated main steam pressure of the generator set, the output is 0. When it is higher than the rated pressure, the output power command feedforward becomes larger. When the pressure reaches a certain value, the slope is increased to increase the output faster. S4, the superimposed command "d" acts on the steam turbine main control. The steam turbine main control is adjusted by the regulator, the output command increases, and the turbine regulating door is opened, thereby increasing the actual power of the unit, thereby reducing the main steam pressure;

[0027] Specifically, when the main steam pressure does not exceed the limit, the speed and accuracy of the load regulation will not be affected, thus avoiding the influence of the previous pressure pull-back loop on the load regulation.

[0028] Specifically, the pressure pull-back loop uses the main steam pressure instruction in the coordinated control system CCS and the actual main steam pressure deviation to correct the power generation instruction.

[0029] Specifically, in S1, the constant C can be set during application. The stronger the heat storage capacity of the boiler and the greater the inertia of the main steam pressure control object, the greater the C value.

[0030] Specifically, in S1, in order to constrain the magnitude of the effect of the predicted value, the obtained value is bidirectionally limited.

[0031] Example 2

[0032] A coordinated control method for preventing main steam overpressure of a thermal power unit comprises the following steps:

[0033] like Figure 1 As shown in the figure, the coordinated control system controls a multivariable strongly coupled system; the two input quantities are: turbine regulating valve opening command Ut, boiler fuel quantity command Ub; the two output quantities are: main steam pressure Pt and unit actual power Ne; the coordinated control system (CCS) is divided into boiler master control (BF) and turbine master control (TF), BF mainly controls the main steam pressure by the fuel quantity, and also affects the power generation load; TF controls the power generation by the turbine regulating valve opening, and also has a direct impact on the main steam pressure.

[0034] like Figure 2 and Figure 4 As shown, S1, take the derivative of the measured main steam pressure signal, the obtained value is the rate of change of the main steam pressure, and multiply it by a constant C to obtain the predicted value of the main steam pressure, and obtain the value "a";

[0035] S2, instruction "a" and main steam pressure are summed to obtain instruction "b";

[0036] S3, instruction "b" is converted into generator power correction instruction "c" through broken line function f(X), and superimposed on the turbine master (TM) power instruction to form power generation instruction "d". The broken line function f(X) takes main steam pressure as input and outputs power instruction, such as Figure 3 As shown, when the input main steam pressure prediction value is lower than the rated main steam pressure of the generator set, the output is 0. When the pressure reaches a certain value, the slope is increased to make the output increase faster. S4, the superimposed instruction "d" acts on the steam turbine main control. The steam turbine main control is adjusted by the regulator, the output instruction increases, and the turbine regulating door is opened, thereby increasing the actual power of the unit, thereby reducing the main steam pressure;

[0037] Specifically, when the main steam pressure does not exceed the limit, the speed and accuracy of the load regulation will not be affected, thus avoiding the influence of the previous pressure pull-back loop on the load regulation.

[0038] Specifically, the pressure pull-back loop uses the main steam pressure instruction in the coordinated control system CCS and the actual main steam pressure deviation to correct the power generation instruction.

[0039] Specifically, in S1, the constant C can be set during application. The stronger the heat storage capacity of the boiler and the smaller the inertia of the main steam pressure control object, the smaller the C value.

[0040] Specifically, in S1, in order to constrain the magnitude of the effect of the predicted value, the obtained value is bidirectionally limited.

[0041] Example 3

[0042] A coordinated control method for preventing main steam overpressure of a thermal power unit comprises the following steps:

[0043] like Figure 1 As shown in the figure, the coordinated control system controls a multivariable strongly coupled system; the two input quantities are: turbine regulating valve opening command Ut, boiler fuel quantity command Ub; the two output quantities are: main steam pressure Pt and unit actual power Ne; the coordinated control system (CCS) is divided into boiler master control (BF) and turbine master control (TF), BF mainly controls the main steam pressure by the fuel quantity, and also affects the power generation load; TF controls the power generation by the turbine regulating valve opening, and also has a direct impact on the main steam pressure.

[0044] like Figure 2 and Figure 4 As shown, S1, take the derivative of the measured main steam pressure signal, the obtained value is the rate of change of the main steam pressure, and multiply it by a constant C to obtain the predicted value of the main steam pressure, and obtain the value "a";

[0045] S2, instruction "a" and main steam pressure are summed to obtain instruction "b";

[0046] S3, instruction "b" is converted into generator power correction instruction "c" through broken line function f(X), and superimposed on the turbine master (TM) power instruction to form power generation instruction "d". The broken line function f(X) takes main steam pressure as input and outputs power instruction, such as Figure 3 As shown, when the pressure is higher than the rated pressure, the output power command feedforward becomes larger. When the pressure reaches a certain value, the slope is increased to make the output increase faster. S4, the superimposed command "d" acts on the steam turbine main control. The steam turbine main control is adjusted by the regulator, the output command increases, and the turbine regulating door is opened, thereby increasing the actual power of the unit, thereby reducing the main steam pressure;

[0047] Specifically, when the main steam pressure does not exceed the limit, the speed and accuracy of the load regulation will not be affected, thus avoiding the influence of the previous pressure pull-back loop on the load regulation.

[0048] Specifically, the pressure pull-back loop uses the main steam pressure instruction in the coordinated control system CCS and the actual main steam pressure deviation to correct the power generation instruction.

[0049] Specifically, in S1, the constant C can be set during application. The stronger the heat storage capacity of the boiler and the greater the inertia of the main steam pressure control object, the greater the C value.

[0050] Specifically, in S1, in order to constrain the magnitude of the effect of the predicted value, the obtained value is bidirectionally limited.

[0051] In summary: Compared with the prior art, the beneficial effects of the present invention are: the thermal power generating unit does not work when it is running at medium and low loads, and only works when the unit is under high load and the main steam pressure is high, which can prevent the boiler main steam pressure from overpressure, thereby ensuring the regulation quality of the power generation and improving the AGC regulation accuracy, and effectively protecting the safety of the boiler.

[0052] Parts not involved in the present invention are the same as the prior art or can be implemented by the prior art. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A coordinated control method for preventing main steam overpressure of a thermal power unit, characterized in that: The following steps are involved: S1. Take the derivative of the measured main steam pressure signal, the value obtained is the rate of change of the main steam pressure, and multiply it by a constant C to obtain the predicted value of the main steam pressure, and obtain the value "a"; S2, command "a" and main steam pressure are summed to obtain command "b"; S3, instruction "b" is converted into generator power correction instruction "c" through broken line function f(X), and then superimposed on the turbine master (TM) power instruction to form power generation instruction "d". The broken line function f(X) takes the main steam pressure as input and outputs the power instruction. When the input main steam pressure prediction value is lower than the rated main steam pressure of the generator set, the output is 0. When it is higher than the rated pressure, the output power instruction feedforward becomes larger. When the pressure reaches a certain value, the slope is increased to make the output increase faster. S4, the superimposed instruction "d" acts on the steam turbine main control, which is adjusted by the regulator, and the output instruction increases, and the turbine regulating door is opened, thereby increasing the actual power of the unit and reducing the main steam pressure; In S1, the constant C can be set when applied. The stronger the heat storage capacity of the boiler and the greater the inertia of the main steam pressure control object, the greater the C value.

2. A coordinated control method for preventing main steam overpressure of a thermal power unit according to claim 1, characterized in that: The logic of main steam pressure and load regulation is: when the main steam pressure does not exceed the limit, it will not affect the speed and accuracy of load regulation, thus avoiding the influence of the previous pressure pull-back loop on load regulation.

3. A coordinated control method for preventing main steam overpressure of a thermal power unit according to claim 2, characterized in that: The pressure pull-back loop uses the main steam pressure instruction in the coordinated control system CCS and the actual main steam pressure deviation to correct the power generation instruction.

4. A coordinated control method for preventing main steam overpressure of a thermal power unit according to claim 1, characterized in that: In the above S1, in order to constrain the magnitude of the effect of the predicted value, the obtained value is subject to bidirectional clipping.

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