Superheated steam temperature control system without water spray after vapor temperature measurement signal

Abstract

The application discloses a kind of overheat steam temperature control systems of no water injection post-steam temperature measurement signal, first controller carries out comprehensive operation to overheat steam temperature measurement value and overheat steam temperature set value and forms overheat temperature reducing water flow demand signal, second controller carries out comprehensive operation to overheat temperature reducing water flow demand signal and temperature reducing water flow measurement value and forms temperature reducing water regulating door opening degree instruction, and MA hand / automatic operation station is controlled temperature reducing water regulating door opening degree, realizes overheat temperature reducing water flow and overheat steam temperature closed-loop control;Using temperature reducing water flow closed-loop control, can accurately control overheat temperature reducing water flow, effectively overcome the non-linear defect of overheat temperature reducing water regulating door valve opening degree-flow, improve the comprehensive regulation quality of overheat steam temperature;And since no water injection post-steam temperature measurement signal that is difficult to accurately reflect temperature reducing water flow change is used, the regulation quality of conventional cascade overheat steam temperature control system is also avoided and the problem that overheat steam temperature automatic control is difficult to realize.

Description

Technical Field

[0001] This invention relates to the field of superheated steam temperature control systems for thermal power unit boilers, and more particularly to a superheated steam temperature control system without a steam temperature measurement signal after water spraying. Background Technology

[0002] The task of superheated steam temperature control in thermal power unit boilers is to keep the superheater outlet steam temperature, i.e., the main steam temperature, within the allowable range. Currently, most thermal power plants use water spray desuperheating devices to control the superheated steam temperature. When using water spray desuperheating devices to regulate superheated steam temperature, the superheater is divided into a pre-heating zone and an inertial zone based on the sensitivity of the node temperature to the effect of the desuperheating water. For example, a cascade PID control system is a method used for superheated steam temperature control in traditional thermal power units, and its control block diagram is shown below. Figure 1 As shown, W a2 (s) is the main loop controller, W a1 (s) is the lead-in zone controller, W o1 (s) is the transfer function of the controlled object in the lead-in zone control, W o2 (s) is the transfer function of the controlled object in the lazy region control, W H1 (s) is the transfer function of the lead signal object and W H2 (s) Transfer function of the master and the controlled variable. r This represents the reference value for the primary controlled variable. d This represents external disturbances in the lead-ahead region. v Represents external disturbances in the inert region. θ 1 represents the dominant modulated quantity, characterizing the physical quantity. θ 2 represents the leading signal characterizing the physical quantity. This type of cascade steam temperature control system often has the characteristics of large delay, large inertia and time-varying nature. It is mainly suitable for systems with basic linearity and dynamic characteristics that do not change with time. Simple proportional control is suitable for situations with small disturbances, small lag, small load changes, low requirements, and allowance for a certain amount of steady-state error. Since the accumulation of integral output is asymptotic, the control action it produces always lags behind the change in deviation. It cannot overcome the influence of disturbances in a timely and effective manner, and it is difficult to stabilize the control system. It has the disadvantage of untimely control. Derivative control cannot eliminate steady-state error, especially for constant deviation input, where there is no control action at all.

[0003] However, because the steam temperature sampling point after water spraying in some boilers is too close to the desuperheater outlet or the desuperheating water flow rate is too large, the steam temperature after water spraying remains near the saturation temperature for a long time. This makes it impossible for the steam temperature after water spraying to accurately reflect the change in the desuperheating water flow rate, causing the cascade steam temperature control system to malfunction and making it difficult to achieve automatic control of the superheated steam temperature.

[0004] In particular, the nonlinear characteristics of the desuperheating water regulating valves of some boilers are quite obvious, which makes the superheated steam temperature regulation speed within the valve opening range slow and oscillate within the valve opening range. This results in poor overall regulation quality of the cascade steam temperature control system and makes it difficult to achieve automatic control of superheated steam temperature (i.e., unable to start automatic, cannot be put into automatic mode, or cannot work normally, and it is difficult to start automatic steam temperature control).

[0005] Therefore, existing technologies still need improvement and development. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a superheated steam temperature control system without a post-spray steam temperature measurement signal, which can improve the overall regulation quality of superheated steam temperature and is easy to realize automatic control of superheated steam temperature.

[0007] The technical solution of the present invention is as follows: a superheated steam temperature control system without a water spraying steam temperature measurement signal, comprising a first controller, a second controller and an MA manual / automatic operation station;

[0008] The superheated steam temperature measurement value is connected to the measurement value interface of the first controller, and the superheated steam temperature setpoint is connected to the setpoint interface of the first controller. The first controller performs comprehensive calculations on the superheated steam temperature measurement value and the superheated steam temperature setpoint, including deviation, proportional, integral, and rate of change, to form the superheater desuperheating water flow demand signal, and outputs the first control command.

[0009] The first control command is connected to the set value interface of the second controller, and the measured value of the desuperheating water flow rate is connected to the measured value interface of the second controller. The second controller performs comprehensive calculations of deviation, proportional, integral and rate of change on the superheater desuperheating water flow rate demand signal and the measured value of the desuperheating water flow rate to form a desuperheating water regulating valve opening command and output the second control command.

[0010] The second control command is output via the MA manual / automatic operator station to control the opening of the desuperheating water regulating valve, thereby achieving closed-loop control of the superheated desuperheating water flow and the superheated steam temperature.

[0011] The superheated steam temperature control system without water spraying and steam temperature measurement signal, wherein: the first controller is a PID controller and the second controller is a PI controller.

[0012] The superheated steam temperature control system without water spraying steam temperature measurement signal, wherein: the first controller is a Smith controller and the second controller is a PI controller.

[0013] The superheated steam temperature control system provided by this invention, which eliminates the need for a post-spray steam temperature measurement signal, employs closed-loop control of the desuperheating water flow rate. This allows for precise control of the superheater desuperheating water flow rate, effectively avoiding the nonlinear characteristics of the superheated desuperheating water regulating valve opening versus flow rate, and unexpectedly improving the overall regulation quality of the superheated steam temperature. Furthermore, by eliminating the use of a post-spray steam temperature measurement signal that is difficult to accurately reflect changes in the desuperheating water flow rate, it also solves the problems of poor regulation quality and difficulty in achieving automatic superheated steam temperature control in conventional cascade superheated steam temperature control systems. Attached Figure Description

[0014] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way; the shapes and proportions of the components in the drawings are merely illustrative and are intended to aid in understanding the invention, and are not intended to specifically limit the shapes and proportions of the components of the invention; those skilled in the art, under the guidance of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0015] Figure 1 This is a control block diagram of a cascaded PID control system in the prior art;

[0016] Figure 2 This is a flowchart illustrating the structure of the superheated steam temperature control system of the present invention.

[0017] Figure 3 This is a structural flowchart of Embodiment 1 of the superheated steam temperature control system of the present invention;

[0018] Figure 4 This is a flowchart illustrating the structure of Embodiment 2 of the superheated steam temperature control system of the present invention. Detailed Implementation

[0019] The specific embodiments and examples of the present invention will be described in detail below with reference to the accompanying drawings. The specific embodiments described are only used to explain the present invention and are not intended to limit the specific embodiments of the present invention.

[0020] like Figure 2 As shown, Figure 2 This is a flowchart illustrating the structure of the superheated steam temperature control system of the present invention. The superheated steam temperature control system of the present invention, which eliminates the need for water spraying and provides a steam temperature measurement signal, consists of a first controller (i.e.,...) Figure 1 Controller 1), second controller (i.e. Figure 1The system consists of controller 2) and MA manual / automatic operation station. The superheated steam temperature measurement value is input to the measurement value interface of the first controller, and the superheated steam temperature setpoint is input to the setpoint interface of the first controller. The first controller performs comprehensive calculations of deviation, proportional, integral, and rate of change on the superheated steam temperature measurement value and the superheated steam temperature setpoint to generate a superheater desuperheating water flow demand signal and outputs a first control command CO. The first control command is input to the setpoint interface of the second controller, and the desuperheating water flow measurement value is input to the measurement value interface of the second controller. The second controller performs comprehensive calculations of deviation, proportional, integral, and rate of change on the superheater desuperheating water flow demand signal and the desuperheating water flow measurement value to generate a desuperheating water regulating valve opening command and outputs a second control command CO. The second control command outputs a control valve opening command via the MA manual / automatic operation station to control the opening of the desuperheating water regulating valve, thereby achieving closed-loop control of the superheated desuperheating water flow and the superheated steam temperature.

[0021] The superheated steam temperature control system provided by this invention, which eliminates the need for a post-spray steam temperature measurement signal, employs closed-loop control of the desuperheating water flow rate. This allows for precise control of the superheater desuperheating water flow rate, effectively overcoming the nonlinearity defect of the superheated desuperheating water regulating valve opening versus flow rate, and unpredictably improving the overall regulation quality of the superheated steam temperature. Furthermore, since it does not use a post-spray steam temperature measurement signal that is difficult to accurately reflect changes in the desuperheating water flow rate, it also avoids the problems of poor regulation quality and difficulty in achieving automatic superheated steam temperature control inherent in conventional cascade superheated steam temperature control systems.

[0022] Example 1, Combination Figure 3 As shown, a PID (Proportion Integration Differentiation) controller is used as the first controller, and a PI (Proportional Integral) controller is used as the second controller.

[0023] The function of proportional control: It reacts to the deviation of the system proportionally. Once a deviation occurs in the system, proportional control immediately produces a regulating effect to reduce the deviation.

[0024] The function of integral control is to eliminate steady-state error and improve the error-free rate of the system. Because there is an error, integral control is performed until there is no error, at which point integral control stops and the integral control output is a constant value.

[0025] The role of derivative adjustment: The derivative value is the rate of change of the deviation value. Only systems with time lag need to add this parameter. If the desired control requirements cannot be achieved by adjusting the proportional and integral parameters, the derivative time can be adjusted.

[0026] PID controllers combine the responsiveness and speed of proportional action, the ability to eliminate steady-state error with integral action, and the predictive control function of derivative action.

[0027] PI controllers are mainly used to improve the steady-state performance of control systems. They are suitable for controlled objects with large inertia and large hysteresis characteristics, such as boiler temperature control.

[0028] Example 2, combined Figure 4 As shown, a Smith controller is used as the first controller and a PI controller is used as the second controller.

[0029] The SMITH controller is a control strategy designed for pure time-delay systems. Also known as the Smith predictor or Smith predictive compensator, it is a pure time-delay compensation control method that weakens and eliminates pure time delay by introducing a compensator connected in parallel with the controlled object.

[0030] In superheated steam temperature control, the controlled object inevitably exhibits some degree of pure time delay. This pure time delay often reduces system stability, degrades dynamic performance, and may cause overshoot and oscillation. The introduction of the Smith predictor effectively compensates for the pure time delay of objects with large time delays, improving the stability and dynamic performance of the superheated steam temperature control system. For superheated steam temperature control systems where stability is the primary requirement and speed is a secondary requirement, the Smith predictor is highly effective.

[0031] Any content not described in detail in this specification belongs to the prior art known to those skilled in the art, such as MA manual / automatic operation stations.

[0032] It should be understood that the above description is only a preferred embodiment of the present invention and is not sufficient to limit the technical solution of the present invention. For those skilled in the art, within the spirit and principles of the present invention, additions, subtractions, substitutions, transformations or improvements can be made based on the above description, and all such additions, subtractions, substitutions or improvements should fall within the protection scope of the appended claims of the present invention.

Claims

1. A superheated steam temperature control system without a post-spray steam temperature measurement signal, characterized in that, It consists of a first controller, a second controller, and an MA manual / automatic operator station; the first controller adopts a Smith controller, which weakens and eliminates pure time delay by introducing a compensator connected in parallel with the controlled object, and the second controller adopts a PI controller; The superheated steam temperature measurement value is connected to the measurement value interface of the first controller, and the superheated steam temperature setpoint is connected to the setpoint interface of the first controller. The first controller performs comprehensive calculations of deviation, proportional, integral and rate of change on the superheated steam temperature measurement value and the superheated steam temperature setpoint to form the superheater desuperheating water flow demand signal and output the first control command. The first control command is connected to the set value interface of the second controller, and the measured value of the desuperheating water flow rate is connected to the measured value interface of the second controller. The second controller performs comprehensive calculations of deviation, proportional, integral and rate of change on the superheater desuperheating water flow rate demand signal and the measured value of the desuperheating water flow rate to form a desuperheating water regulating valve opening command and output the second control command. The second control command is output via the MA manual / automatic operator station to control the opening of the desuperheating water regulating valve, thereby achieving closed-loop control of the superheated desuperheating water flow rate and the superheated steam temperature.

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