Gas turbine unit waste heat boiler main steam temperature control method based on PID controller with acceleration term

Abstract

The application discloses a gas turbine unit waste heat boiler main steam temperature control method based on a PID controller with an acceleration term, belongs to the field of power plant thermal power engineering, and solves the problems of slow response to external disturbance and set value step change, lack of sensing ability for main steam temperature acceleration change, difficult controller parameter setting and strong subjectivity of the prior art method. The method comprises the following steps: introducing the PID controller with an acceleration term in a conventional lead differential main steam temperature control strategy of the gas turbine unit waste heat boiler, and adopting a setting method of the PID controller with an acceleration term based on a simplified prediction model to set parameters of the controller. The application can effectively inhibit fluctuation and oscillation of the main steam temperature of the gas turbine unit waste heat boiler caused by disturbance of the flue gas side or the working medium side, effectively reduce the maximum dynamic deviation of the main steam temperature, and improve the control performance of the main steam temperature control system of the waste heat boiler during rapid load change of the gas turbine unit.

Description

Technical Field

[0001] This invention belongs to the field of power plant thermal power engineering, specifically relating to a method for controlling the main steam temperature of a gas turbine unit waste heat boiler based on a PID controller with an acceleration term. Background Technology

[0002] The main steam temperature control system of the waste heat boiler in a gas turbine unit is one of the key control systems for ensuring the safe and economical operation of the unit. Main steam temperature, as an important thermodynamic parameter, directly affects the unit's thermal efficiency, equipment safety, and service life. Excessively high main steam temperature can lead to a decrease in the strength of superheater tubes, accelerate metal creep, shorten equipment life, and in severe cases, may even cause tube rupture accidents. Conversely, excessively low main steam temperature will reduce the unit's cycle thermal efficiency, increase the humidity of the turbine's last-stage blades, and affect the unit's safe operation. Therefore, controlling the main steam temperature within the allowable deviation range of the set value is of great significance for ensuring the safe and efficient operation of the gas turbine unit.

[0003] Currently, the main steam temperature control of the waste heat boiler in gas turbine units is mainly achieved by adjusting the opening of the desuperheating water spray valve to inject low-temperature atomized water into the main steam pipeline. In terms of control strategies, the most typical and widely used technology in industrial settings is the dual-loop control technology with lead-ahead differential.

[0004] However, with the increasing demand for gas turbine units to participate in grid peak shaving and frequency regulation, the rapid load change operation of the units is becoming more frequent. Traditional PID control strategies are gradually revealing the following technical shortcomings when dealing with these complex operating conditions: First, the response to external disturbances and abrupt changes in the setpoint is slow. Due to the long steam pipelines and the fact that the main steam temperature system of the waste heat boiler in the gas turbine unit consists of multiple heat exchangers connected in series, its dynamic characteristics exhibit high-order inertial characteristics. Traditional PID controllers typically employ conservative "slow adjustment" parameter settings to ensure system stability. Internal disturbances can be eliminated in advance using the lead differential signal. However, for external disturbances such as flue gas disturbances and load command changes, as well as abrupt changes in the main steam temperature setpoint, traditional PID controllers lack effective rapid adjustment capabilities, resulting in large dynamic deviations and long recovery times in the main steam temperature.

[0005] Secondly, traditional PID controllers lack the ability to sense changes in the acceleration of main steam temperature. Their highest order is first-order (i.e., only containing a derivative element), meaning their control action can only predict and respond to the rate of change of main steam temperature, but cannot sense or utilize the acceleration information of the main steam temperature. In scenarios requiring advance adjustment to suppress temperature fluctuations, the predictability and adjustment accuracy of traditional PID controllers are limited, making it difficult to achieve more precise proactive control.

[0006] Third, the tuning of controller parameters is difficult and highly subjective. The optimization and tuning of traditional PID controllers lacks a systematic engineering method and relies heavily on the experience of the commissioning personnel for repeated trial and error. The tuning process is time-consuming and laborious, and is greatly affected by the subjective factors of the commissioning personnel. This results in significant differences in control performance between different units or different commissioning personnel, making it difficult to guarantee the consistency and optimality of control quality.

[0007] To address the aforementioned issues, we propose a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term. This method solves the problems of slow response to external disturbances and step changes in setpoints, lack of perception of changes in main steam temperature acceleration, and difficulty and subjectivity in tuning controller parameters.

[0009] This invention is implemented as follows: a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term, the method comprising: In the conventional pilot differential main steam temperature control strategy of the waste heat boiler of the gas turbine unit, a PID controller with acceleration term is introduced, and the parameter tuning of the controller is carried out by the tuning method of the PID controller with acceleration term based on the simplified prediction model. The transfer function of the PID controller with acceleration term is expressed as: In the formula For the Laplace transform of a PID controller with an acceleration term, For Lagrange operators, For the proportional gain of the controller, For the integral time of the controller, For differential time, For acceleration time.

[0010] Preferably, the tuning method for the PID controller with acceleration term based on the simplified prediction model includes the following parameter tuning method: Establish a simplified prediction model for a PID controller with an acceleration term; An open-loop step test was conducted on the main steam temperature system. Open-loop step response data were collected, and the start time of the open-loop step was defined as time point 0. The time points t5, t6, and t7 corresponding to the main steam temperature reaching 5%, 35%, and 85% of the final steady-state increment during the step response were recorded. 35 t 85 ; Obtain time points t5 and t 35 t85 Based on time points t5 and t 35 t 85 Calculate the parameters of the simplified prediction model; The tuning parameters of the PID controller with acceleration term are calculated based on the simplified prediction model parameters.

[0011] Preferably, the transfer function of the simplified prediction model of the PID controller with acceleration term is expressed as: In the formula, This represents the simplified Laplace transform of the prediction model. The process gain of the main steam temperature system. The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. Pure delay time of the main steam temperature system It is a Lagrange operator.

[0012] Preferably, the step based on time points t5 and t 35 t 85 When calculating the parameters of the simplified prediction model, the calculation formula is expressed as follows: in, The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. This refers to the pure delay time of the main steam temperature system.

[0013] Compared with the prior art, the embodiments of this application have the following main advantages: This invention can effectively suppress the fluctuation and oscillation of the main steam temperature of the waste heat boiler in gas turbine units caused by disturbances on the flue gas side or working fluid side, effectively reduce the maximum dynamic deviation of the main steam temperature, and improve the control performance of the main steam temperature control system of the waste heat boiler during rapid load changes in gas turbine units. Attached Figure Description

[0014] Figure 1 The schematic diagram of the traditional dual-loop control technology with lead-ahead differential is shown.

[0015] Figure 2 A schematic diagram of the principle of the main steam temperature control method for waste heat boiler of gas turbine unit based on PID controller with acceleration term is shown. Detailed Implementation

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0017] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0018] The target of the main steam temperature control for the waste heat boiler of the gas turbine unit is the main steam temperature. The main steam temperature is controlled by injecting low-temperature atomized water into the main steam pipeline through the desuperheating water spray valve. It is a key control system to ensure the quality of the main steam temperature of the waste heat boiler of the gas turbine unit. Figure 1 The diagram illustrates the principle of a traditional dual-loop control technology with a lead-in differential loop. Currently, most typical main steam temperature control methods employ this traditional dual-loop control technology with a lead-in differential loop (as shown in the attached diagram). Figure 1 As shown), the Laplace transform calculation expression for the controlled water spray valve opening command U(s) is: Existing methods are slow to respond to external disturbances and step changes in setpoints, lack the ability to sense changes in main steam temperature acceleration, and are difficult and subjective in controlling parameter tuning. To address these issues, we propose a main steam temperature control method for gas turbine waste heat boilers based on a PID controller with an acceleration term. In short, the method involves introducing a PID controller with an acceleration term into the conventional lead-differential main steam temperature control strategy for the gas turbine waste heat boiler, and using a tuning method based on a simplified prediction model to tune the controller parameters. This invention can effectively suppress fluctuations and oscillations in the main steam temperature of the gas turbine waste heat boiler caused by disturbances on the flue gas or working fluid side, effectively reduce the maximum dynamic deviation of the main steam temperature, and improve the control performance of the main steam temperature control system for the waste heat boiler during rapid load changes in the gas turbine unit.

[0019] This invention provides a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term. Figure 2A schematic diagram of a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term is shown. The method specifically includes: In the conventional pilot differential main steam temperature control strategy of the waste heat boiler of the gas turbine unit, a PID controller with acceleration term is introduced, and the parameter tuning of the controller is carried out by the tuning method of the PID controller with acceleration term based on the simplified prediction model. In this embodiment of the invention, the traditional PID controller in the conventional lead-ahead differential main steam temperature control strategy of the waste heat boiler of the gas turbine unit is replaced with a PID controller with an acceleration term. This PID controller with acceleration term retains the proportional, integral, and derivative components of the traditional PID controller, but adds an acceleration component to sense the acceleration changes in the main steam temperature, thereby improving the control system's ability to suppress external disturbances and maintain the main steam temperature setpoint. The transfer function of the PID controller with acceleration term is expressed as follows: In the formula For the Laplace transform of a PID controller with an acceleration term, For Lagrange operators, For the proportional gain of the controller, For the integral time of the controller, For differential time, For acceleration time.

[0020] In a further preferred embodiment of the present invention, the method for tuning the parameters of the PID controller with acceleration term based on the simplified prediction model includes: Establish a simplified prediction model for a PID controller with an acceleration term; The transfer function of the simplified prediction model of the PID controller with acceleration term is expressed as follows: In the formula, This represents the simplified Laplace transform of the prediction model. The process gain of the main steam temperature system. The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. Pure delay time of the main steam temperature system It is a Lagrange operator.

[0021] An open-loop step test was conducted on the main steam temperature system. Open-loop step response data were collected, and the start time of the open-loop step was defined as time point 0. The time points t5, t6, and t7 corresponding to the main steam temperature reaching 5%, 35%, and 85% of the final steady-state increment during the step response were recorded. 35 t 85.

[0022] Obtain time points t5 and t 35 t 85 Based on time points t5 and t 35 t 85 Calculate the parameters of the simplified prediction model; Among them, the time point t5, t 35 t 85 When calculating the parameters of the simplified prediction model, the calculation formula is expressed as follows: in, The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. The pure delay time of the main steam temperature system, and the process gain of the main steam temperature system. The ratio of the final change in main steam temperature to the step amount of the desuperheating valve during the open-loop step process can be used to determine the temperature.

[0023] The tuning parameters of the PID controller with acceleration term are calculated based on the simplified prediction model parameters.

[0024] The formula for calculating the tuning parameters of the PID controller with acceleration term is expressed as follows: Where, in the formula, For the third-order coefficients of the process model, For the second-order coefficients of the process model, These are the first-order coefficients of the process model.

[0025] In this embodiment, the simplified prediction model adopts a series structure of first-order and second-order inertial elements and includes a pure time delay element to describe the high-order inertial characteristics of the main steam temperature system. The pure time delay time and the pure time delay coefficient together determine the time delay characteristics of the system, the first inertial time determines the dominant inertial characteristics of the system, and the control method controls the maximum dynamic deviation of the main steam temperature within 6°C under the rapid load change condition of the gas turbine.

[0026] In summary, this invention provides a method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term. This invention can effectively suppress the fluctuation and oscillation of the main steam temperature of the waste heat boiler in a gas turbine unit caused by disturbances on the flue gas side or the working fluid side, effectively reduce the maximum dynamic deviation of the main steam temperature, and improve the control performance of the main steam temperature control system of the waste heat boiler during rapid load changes in the gas turbine unit.

[0027] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions are also within the scope of protection of the present invention.

Claims

1. A method for controlling the main steam temperature of a waste heat boiler in a gas turbine unit based on a PID controller with an acceleration term, characterized in that, The method includes: In the conventional pilot differential main steam temperature control strategy of the waste heat boiler of the gas turbine unit, a PID controller with acceleration term is introduced, and the parameter tuning of the controller is carried out by the tuning method of the PID controller with acceleration term based on the simplified prediction model. The transfer function of the PID controller with acceleration term is expressed as: In the formula For the Laplace transform of a PID controller with an acceleration term, For Lagrange operators, For the proportional gain of the controller, For the integral time of the controller, For differential time, For acceleration time.

2. The method for controlling the main steam temperature of a gas turbine unit waste heat boiler based on a PID controller with an acceleration term as described in claim 1, characterized in that: The tuning method for the PID controller with acceleration term based on the simplified prediction model includes the following parameter tuning method for the controller: Establish a simplified prediction model for a PID controller with an acceleration term; An open-loop step test was conducted on the main steam temperature system. Open-loop step response data were collected, and the start time of the open-loop step was defined as time point 0. The time points t5, t6, and t7 corresponding to the main steam temperature reaching 5%, 35%, and 85% of the final steady-state increment during the step response were recorded. 35 t 85 .

3. The method for controlling the main steam temperature of a gas turbine waste heat boiler based on a PID controller with an acceleration term as described in claim 2, characterized in that: The tuning method for the PID controller with acceleration term based on the simplified prediction model further includes: Obtain time points t5 and t 35 t 85 Based on time points t5 and t 35 t 85 Calculate the parameters of the simplified prediction model; The tuning parameters of the PID controller with acceleration term are calculated based on the simplified prediction model parameters.

4. The method for controlling the main steam temperature of a gas turbine waste heat boiler based on a PID controller with an acceleration term as described in claim 3, characterized in that: The transfer function of the simplified prediction model of the PID controller with acceleration term is expressed as: In the formula, This represents the simplified Laplace transform of the prediction model. The process gain of the main steam temperature system. The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. Pure delay time of the main steam temperature system It is a Lagrange operator.

5. The method for controlling the main steam temperature of a gas turbine unit waste heat boiler based on a PID controller with an acceleration term as described in claim 4, characterized in that: The basis of time points t5 and t 35 t 85 When calculating the parameters of the simplified prediction model, the calculation formula is expressed as follows: in, The first inertial time of the main steam temperature system. The pure delay time coefficient of the main steam temperature system. This refers to the pure delay time of the main steam temperature system.

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