Auxiliary feedforward direct energy balance control method for supercritical units

Abstract

The present invention discloses an auxiliary feedforward direct energy balance control method applicable to supercritical units, belonging to the technical field of coordinated control of supercritical thermal power units. The method includes obtaining a steam turbine energy demand signal correction value BD and a supercritical unit boiler heat signal HR; and using the difference Δe between the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR as a boiler master control auxiliary feedforward, thereby ensuring that the main steam pressure and load control are balanced; the method reconstructs the direct energy balance strategy applicable to subcritical units, making it applicable to the model of direct current boilers, and applies it to boiler master control feedforward, and participates in the regulation of boiler master control in a small range. The problem of unqualified AGC indicators caused by frequent load lock-in increase and decrease due to large main steam pressure deviation is solved, and the AGC performance indicators of the unit are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coordinated control of supercritical thermal power units, and more specifically, to an auxiliary feedforward direct energy balance control method suitable for supercritical units. Background Art

[0002] The design of the coordinated control system of supercritical thermal power units adopts the IEB (Indirect Energy Balance) control method. The characteristic differences between boilers and steam turbines are coordinated through the corresponding feedforward of the unit load command and the corresponding feedforward of the machine front pressure. With the changes in the coal-fired power market, the combustion of coal-blended thermal power units has become the norm, but the above control strategy has not been adjusted and matched according to the actual operating conditions. Therefore, after the normal operation of the thermal power unit, the machine front pressure response effect often has the problem of good and bad, which often causes a large deviation in the main steam pressure control, and then the pressure is locked and the AGC is exited. Especially when the unit load changes greatly, the boiler main control effect is often poor. Summary of the invention

[0003] The purpose of the present invention is to propose an auxiliary feedforward direct energy balance control method suitable for supercritical units. This method reconstructs the direct energy balance strategy suitable for subcritical units, makes it suitable for the model of direct-flow boilers, and applies it to boiler master control feedforward, and participates in the adjustment of boiler master control in a small range. It solves the problem of unqualified AGC indicators caused by frequent load lock-in increase and decrease due to large main steam pressure deviation, and improves the AGC performance indicators of the unit.

[0004] To achieve the above object, the present invention adopts the following technical solution: an auxiliary feedforward direct energy balance control method suitable for supercritical units, characterized in that the method comprises:

[0005] ① Obtain the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR;

[0006] ② The difference Δe between the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR is used as auxiliary feedforward for the boiler master control, thereby ensuring that the main steam pressure Pt is balanced with the load control;

[0007] in,

[0008] P1 represents the regulating stage pressure, Pt represents the main steam pressure, Ps represents the main steam pressure setting value, Pf represents the separator outlet pressure of the supercritical unit, K represents the adjustment coefficient of the differential intensity of the energy demand signal, and C represents the heat storage coefficient.

[0009] Furthermore, the process of obtaining the steam turbine energy demand signal correction value BD is as follows:

[0010] Send the regulating stage pressure P1 signal and the main steam pressure Pt signal to the divider module to obtain the intermediate variable The intermediate variable The main steam pressure set value Ps signal is sent to the first multiplier module to obtain the energy demand signal of the steam turbine

[0011] The energy demand signal of the steam turbine It is divided into three paths. The first path is the energy demand signal of the steam turbine. Sent to the first differentiator module to obtain the differential of the energy demand signal of the steam turbine The energy demand signal of the steam turbine is obtained by differential The signal is input to the second multiplier module;

[0012] Energy demand signal of the second steam turbine The second multiplier module receives the energy demand signal of the steam turbine. and the differential of the turbine energy demand signal The signal is multiplied to obtain the differential of the corrected turbine energy demand signal The differential of the corrected turbine energy demand signal is The signal is transmitted to the proportional module, which adjusts the differential of the corrected steam turbine energy demand signal. Signal strength, obtain adjustable turbine energy demand signal differential K is the adjustment coefficient of the differential strength of the energy demand signal. Its default value is 1. When the dynamic adjustment strength needs to be strengthened, the K value is increased. When the dynamic adjustment strength needs to be weakened, the K value is reduced and the differential strength of the energy demand signal of the adjustable steam turbine is increased. The signal is transmitted to the first adder module;

[0013] Energy demand signal of the third steam turbine The first adder module receives the adjustable steam turbine energy demand signal differential component. signal and turbine energy demand signal Perform addition operation to obtain the turbine energy demand signal correction value BD;

[0014] Furthermore, the acquisition process of the supercritical unit boiler heat signal HR is as follows: first, the separator outlet pressure Pf signal of the supercritical unit is sent to the second differentiator module, and after being differentiated by the second differentiator module, it is sent to the second adder module together with the regulating stage pressure P1 signal to obtain the boiler heat signal HR of the supercritical unit. C represents the heat storage coefficient.

[0015] Through the above design scheme, the present invention can bring the following beneficial effects: by reconstructing the direct energy balance control strategy, it is applied to the boiler master control feedforward of the coordinated control of the supercritical unit, realizing the universal application of the strategy from drum boilers to direct current boilers. After adjusting its coefficient, it acts on the boiler master control in a small range. The reconstruction retains the core content of direct energy balance control, takes advantage of its advantages, and adds a dynamic differential signal of heat storage when the power changes. Through the coefficient, the degree of influence of this transformation on the boiler master control is adjusted to achieve balance. Field application shows that this application solves the problem of unqualified AGC indicators caused by frequent load lock-in and increase and decrease due to large deviation of the main steam pressure, improves the AGC performance indicators, and has a good reference role for similar projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are used to provide a further understanding of the present invention and constitute a part of the present application. The exemplary embodiments of the present invention and their descriptions are used to understand the present invention and do not constitute improper limitations of the present invention. In the accompanying drawings:

[0017] Figure 1 It is a control logic diagram of an auxiliary feedforward direct energy balance control method applicable to supercritical units;

[0018] Figure 2 The load variation curve diagram of the unit after optimization by the auxiliary feedforward direct energy balance control method proposed by the present invention;

[0019] In the figure: 1-divider module, 2-first multiplier module, 3-first differentiator module, 4-second multiplier module, 5-proportional module, 6-first adder module, 7-second differentiator module, 8-second adder module.

[0020] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0021] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the present invention is clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the present invention is not limited to the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. In order to avoid confusing the essence of the present invention, known methods, processes, processes, components and circuits are not described in detail. In the description of the present invention, it should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0022] like Figure 1 As shown, an auxiliary feedforward direct energy balance control method suitable for a supercritical unit includes:

[0023] ① Obtain the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR;

[0024] ② The difference Δe between the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR is used as auxiliary feedforward for the boiler master control, thereby ensuring that the main steam pressure Pt is balanced with the load control;

[0025] The process of obtaining the turbine energy demand signal correction value BD is as follows:

[0026] The regulating stage pressure P1 signal (this signal is the unit state parameter measurement signal) and the main steam pressure Pt signal are sent to the divider module 1 to obtain the intermediate variable The intermediate variable The main steam pressure set value Ps signal is sent to the first multiplier module 2 to obtain the energy demand signal of the steam turbine Considering the dynamic change of power demand, the corresponding energy change on the boiler supply side, and the change of steam flow rate, the heat storage capacity of the boiler will also change. Therefore, the differential signal of the required steam flow rate is added to convert the energy demand signal of the steam turbine into It is divided into three paths. The first path is the energy demand signal of the steam turbine. Sent to the first differentiator module 3, the differential of the energy demand signal of the steam turbine is obtained The energy demand signal of the steam turbine is obtained by differential The signal is input into the second multiplier module 4; at the same time, it is also necessary to correct the differential of the turbine energy demand signal according to the different operating loads of the unit, because the energy demand signal of the steam turbine Proportional to the unit load, so the energy demand signal of the steam turbine can be used The differential of the energy demand signal of the steam turbine is corrected. The energy demand signal of the second steam turbine The energy demand signal of the steam turbine obtained by the first multiplier module 2 is sent to the second multiplier module 4. The differential of the energy demand signal of the steam turbine is obtained by outputting the first differentiator module 3. The signal is simultaneously sent to the second multiplier module 4 to obtain the differential of the corrected steam turbine energy demand signal The differential of the corrected turbine energy demand signal is The signal is sent to the proportional module 5, which adjusts the differential of the corrected turbine energy demand signal through the coefficient K. Signal strength, obtain adjustable turbine energy demand signal differential K is the adjustment coefficient of the differential strength of the energy demand signal. Its default value is 1. When the dynamic adjustment strength needs to be strengthened, the K value is increased. When the dynamic adjustment strength needs to be weakened, the K value is reduced and the differential strength of the energy demand signal of the adjustable steam turbine is increased. The signal is transmitted to the first adder module 6; the energy demand signal of the third steam turbine The first adder module 6 receives the adjustable energy demand signal of the steam turbine and calculates the differential component of the energy demand signal of the steam turbine. signal and turbine energy demand signal Perform addition operation to obtain the turbine energy demand signal correction value BD;

[0027] In the direct energy balance of a subcritical unit, the boiler heat is represented by the differential of the regulating stage pressure P1 plus the drum pressure Pd, which represents the amount of fuel entering the boiler. However, for a direct current boiler, there is no drum, so we can only find new physical quantities to characterize the change in boiler energy. The separator of a supercritical unit plays the role of a boiler drum in a subcritical unit. Therefore, the change in the separator outlet pressure Pf can represent the change in the heat storage of the boiler of the supercritical unit. The implementation method is as follows: first, the separator outlet pressure Pf signal of the supercritical unit is sent to the second differentiator module 7, and is sent to the second adder module 8 together with the regulating stage pressure P1 signal to obtain the boiler heat signal of the supercritical unit. C represents the heat storage coefficient.

[0028] Since the heat storage capacity of the DC furnace is relatively small, in the DC furnace control, direct energy balance control can be used as an auxiliary feedforward to reasonably control the size of the coefficient C, overcome the internal disturbance of the boiler, and slightly affect the boiler main control, so as to give full play to the advantages of direct energy balance control in quickly maintaining dynamic and static energy balance. Therefore, the difference Δe between BD and HR can be used as a small auxiliary feedforward for the boiler main control.

[0029]

[0030] The reconstructed direct energy balance strategy was applied to a supercritical unit. Before the optimization, the unit frequently had large deviations in the main steam pressure Pt when the load was increased or decreased, which locked the increase or decrease of the load, causing the unit to exit the CCS mode and seriously fail to meet the AGC indicators. The fundamental reason is that when the unit load changes, the load and the main steam pressure Pt are out of coordination. After optimization according to the auxiliary feedforward type direct energy balance control strategy, the control of the direct current boiler was applied. During the load change process, the maximum dynamic deviation of the main steam pressure Pt was 0.63MPa, and the main steam pressure Pt was balanced with the load control. The control effect diagram is shown in the figure below. Figure 2 As shown, Figure 2 Where a represents the load instruction; b represents the unit load; Ps represents the main steam pressure setting value; and Pt represents the main steam pressure.

[0031] The divider module 1, the first multiplier module 2, the first differentiator module 3, the second multiplier module 4, the proportional module 5, the first adder module 6, the second differentiator module 7 and the second adder module 8 described in the present invention are all common components in the power system. The method proposed in the present invention organically integrates and combines the above-mentioned devices or modules into a whole. It should be emphasized that, as far as the above-mentioned devices or modules are concerned, the specific structures for realizing their respective functions already exist in the prior art, and the protocols, software or programs involved in the work processing of each device and / or module also already exist in the prior art, and are fully known to those skilled in the art.

Claims

1. An auxiliary feedforward direct energy balance control method suitable for supercritical units, characterized in that: The method includes: ① Obtain the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR; ② The difference Δe between the steam turbine energy demand signal correction value BD and the supercritical unit boiler heat signal HR is used as auxiliary feedforward for the boiler master control, thereby ensuring that the main steam pressure Pt is balanced with the load control; in, P1 represents the regulating stage pressure, Pt represents the main steam pressure, Ps represents the main steam pressure setting value, Pf represents the separator outlet pressure of the supercritical unit, K represents the adjustment coefficient of the differential intensity of the energy demand signal, and C represents the heat storage coefficient.

2. The auxiliary feedforward direct energy balance control method for supercritical units according to claim 1, characterized in that: The process of obtaining the turbine energy demand signal correction value BD is as follows: The regulating stage pressure P1 signal and the main steam pressure Pt signal are sent to the divider module (1) to obtain the intermediate variable The intermediate variable The main steam pressure setting value Ps signal is sent to the first multiplier module (2) to obtain the energy demand signal of the steam turbine The energy demand signal of the steam turbine It is divided into three paths. The first path is the energy demand signal of the steam turbine. The signal is sent to the first differentiator module (3) to obtain the differential of the energy demand signal of the steam turbine. The energy demand signal of the steam turbine is obtained by differential The signal is input into the second multiplier module (4); Energy demand signal of the second steam turbine The second multiplier module (4) receives the energy demand signal of the steam turbine. and the differential of the turbine energy demand signal The signal is multiplied to obtain the differential of the corrected turbine energy demand signal The differential of the corrected turbine energy demand signal is The signal is transmitted to the proportional module (5), and the proportional module (5) adjusts the differential of the corrected steam turbine energy demand signal. Signal strength, obtain adjustable turbine energy demand signal differential The energy demand signal of the adjustable steam turbine is differentially The signal is transmitted to the first adder module (6); Energy demand signal of the third steam turbine The first adder module (6) receives the adjustable steam turbine energy demand signal differential component. signal and turbine energy demand signal Perform addition operation to obtain the turbine energy demand signal correction value BD; 3. The auxiliary feedforward direct energy balance control method for supercritical units according to claim 1, characterized in that: The acquisition process of the boiler heat signal HR of the supercritical unit is as follows: first, the separator outlet pressure Pf signal of the supercritical unit is sent to the second differentiator module (7), and after being differentiated by the second differentiator module (7), it is sent together with the regulating stage pressure P1 signal to the second adder module (8) to obtain the boiler heat signal HR of the supercritical unit. C represents the heat storage coefficient.

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