Superheated Steam Temperature Control Research Articles

Event‐triggered networked cascade control systems design subject to hybrid attacks

This paper deals with the design problem of networked cascade control systems (NCCSs) with two different event‐triggered mechanisms (ETMs) for the feedback loops. A combination of stochastic denial‐of‐service (DoS) attack and deception attack has been considered for the communication network. To comply with the practical point of view, the primary and the secondary systems have been considered with distinct disturbances. First, the closed‐loop system with state feedback controllers is provided in a unified stochastic delayed system. Then, the Lyapunov–Krasovskii stability theory and stochastic analysis techniques are employed to derive and formulate control design conditions in terms of linear matrix inequalities (LMIs). Finally, a superheater steam temperature control is utilized to assess the applicability of the proposed method.

Robust compensation for active disturbance rejection control of a class of high‐order systems with large time delay: Simulation and experimental studies

AbstractRejection of unknown disturbances and uncertainties in high‐order nonlinear systems with large delays is an important control problem. Active disturbance rejection control (ADRC) solves disturbances and uncertainties in a simple and effective way. In engineering, low‐order ADRC is often used to control high‐order large‐delay systems because of its ease of implementation and simplicity of operation. However, this leads to the problem that the low‐order ADRC has a limited ability to configure the high‐order nonlinear systems. The desired dynamics and the closed‐loop dynamics are almost always very biased. For a class of high‐order nonlinear systems with delay, a bias feedback compensation (BFC) approach to ADRC is suggested. This strategy works by adding a feedback loop based on the desired dynamics over the ADRC loop. The BFC strategy can improve the poor performance of low‐order ADRC for higher‐order nonlinear systems. In addition, a synthesis parameter tuning procedure of BFC‐ADRC is proposed in this article. Then, the stability problem is analyzed in this article. Finally, high‐fidelity simulation studies on a 1000 MW power plant for superheater steam temperature control and experiments on three interacting water tanks for level control are performed to verify the tracking, disturbance rejection, and robustness of the control strategy. Both simulation and experiments show that the method is highly robust and significantly improves both disturbance rejection and tracking performance.

A hybrid receding horizon optimization and active disturbance rejection control of boiler superheated steam temperature

Efficient control of superheated steam temperature is critical for maintaining the safety and efficiency of a power plant boiler. Exceeding the safe temperature range can cause irreversible damage. However, unknown disturbances and uncertainties, as well as large delay dynamics, often make superheated steam temperature safety control challenging. To this end, this paper proposes a hybrid bi-level safety control for superheated steam temperature control in a power plant boiler. The bottom level uses active disturbance rejection control, while upper level uses receding horizon optimization. The proposed method combines the advantages of active disturbance rejection control in solving unknown disturbances and the dynamic optimization of receding horizon optimization to effectively and safely control superheated steam temperature and optimize the control system performance. The main novelty of the scheme lies in making receding horizon optimization independent of the model of the plant, in terms of making full use of the closed-loop desired dynamics under active disturbance rejection control. Practical synthesis design methods are also presented to illustrate the tuning and optimization of this control strategy. On-site testing results show that the proposed method improves both disturbance rejection and tracking performance, with improvements of at least 20 % over comparison methods. In conclusion, the proposed bi-level control strategy is a promising approach for improving the safety and efficiency of power plants.

Robust regulation for superheated steam temperature control based on data-driven feedback compensation

Control of the superheated steam temperature is a significant technical challenge to coal-fired power plants due to the strong nonlinearity, large inertia and parameter uncertainties with external disturbances. This paper proposes a robust proportion–integration–differentiation (PID) control of the superheated steam temperature with proven stability and the external disturbance rejection. The design is based on the proposed data-driven feedback compensator (DFC) which is a neural network (NN) trained to isolate the nonlinearity and inertia from the PID controller, allowing the system for tuning the PID controller can be simplified as an approximate linear system with the modeling error based-feedback and feed-forward compensations. Then, the PID controller is tuned by the Nyquist stability criterion to place every closed-loop pole to a specific region in the left-half s-plane to guarantee the stability with considering the modeling error. Besides, a NN based feed-forward compensator is trained as the inverse model of the feedback compensator to further smooth the temperature fluctuation caused by the disturbance. The simulations and engineering implementation of the superheated steam temperature controls for a coal-fired power plant in Australia show the effectiveness.

Innovative Sensor Design Method of Industrial Ceramic Product Modeling Based on Immune Optimization Algorithm

A new method based on immune optimization algorithm was proposed for modeling and design of industrial ceramic products. Based on the joint coding of fuzzy rules and membership function parameters, an improved immune optimization algorithm was used to realize the synchronous optimization of industrial ceramic product modeling. A superheated steam temperature control system is taken as an example to carry out simulation tests. The results show that the ratio of the unit volume to the side length is between 0 and 1, which is called the mass of the grid element. Zero is the worst quality and one is the best. Element aspect ratio and distortion degree are also basic inspection indexes. The average mass of vacuum glass is 0.86, the aspect ratio is 1.71, and the element distortion degree is 0.13, indicating that the grid quality is well divided. It is proved that using the improved immune genetic algorithm to optimize fuzzy control can overcome the defects of the traditional genetic algorithm and ensure the faster and more stable search for the optimal rule base and membership function.

Multi-model adaptive predictive control of superheated steam temperature of DSG solar parabolic-trough collector based on heat-steam ratio and its reference trajectory

The direct steam generation (DSG) solar thermal power generation system has obvious inertia and nonlinearity in the response of superheated steam temperature. Due to the intermittent and random fluctuations of solar irradiation, the DSG system frequently undergoes large changes in operating conditions, which results in a very complicated problem of controlling the superheated steam temperature at the collector outlet. This paper proposed a multi-model adaptive control scheme based on the heat-steam ratio and its reference trajectory for the control problem of the outlet steam temperature of the DSG solar parabolic-trough collector. Firstly, through analyzing the dynamic characteristics of the superheated steam temperature, the main factors and the main nonlinear characteristics that lead to the nonlinearity of the steam temperature response are revealed. Secondly, taking the ratio of solar irradiation to the outlet steam flow (heat-steam ratio) as the characteristic parameter based on the nonlinear characteristics of the system, the DSG collector system is divided into several linearized subspaces, and then the corresponding steam temperature predictive sub-model set and steam temperature adaptive predictive control scheme are established. Finally, a smooth switching strategy based on the reference trajectory of the nonlinear characteristic parameter (heat-steam ratio) is established in response to the frequent or large switching of the controller caused by the large changes in the operating conditions, which effectively improved the stability of the temperature control process of the superheated steam at the DSG collector outlet. In this paper, the effectiveness of the above-mentioned control scheme has been preliminarily verified through simulation experiments.

Application of anti integral saturation cascade PID control algorithm in superheated steam temperature control

At present, most units adopt the superheated steam temperature control system with cascade PID control structure. However, because most cascade PID control algorithms have no anti-integral saturation function, the automatic control of boiler superheated steam temperature cannot be put into operation normally. On the existing cascade PID superheated steam temperature regulation system, we judge the deviation value of the main regulator and the output value of the auxiliary regulator, and cancel the integration function at an appropriate time. When the input deviation signal turns over, the regulating system can immediately enter the normal regulating state, so that the cascade PID superheated steam temperature regulating system can timely and accurately regulate the superheated steam temperature. The fuel cost is saved by about 155,600 yuan per year.

Configuration Design of Superheated Steam Temperature Control for No.2 Unit of Diaobingshan Power Plant

Configuration Design of Superheated Steam Temperature Control for No.2 Unit of Diaobingshan Power Plant

Application of Iterative Feedback Tuning Method in Superheated Steam Temperature Control System

Taking a 600 MW supercritical once-through boiler as the study object, this paper designed an IFT-based two-degree-of-freedom (DOF) PID superheated steam temperature control system. Besides, the IFT-PID controller was formed and compared with the conventional tuning method. The simulation results show that this method can be successfully applied to great-inertia and large-lag controlled objects, with evident superiority.

PID Controllers with a Constant Speed Actuator: Implementation Versions and Self-Tuning of Pulse Duration

The article considers three implementation versions of controllers operating with constant speed actuators that are used in automation systems of a technological process: with a relay-pulse control unit (RPCU) with a lagging feedback and topping differentiator (a real differentiating element, RD), with calculating the output according to a PID algorithm and using the actuator model for its implementation, and with calculating the control output speed and using a pulse-width modulator. Formulas for calculating the parameters of the RPCU and RD primary components from the condition of approaching the equivalent PID algorithm are given. The system version with a PID controller with the actuator control proceeding from its model is considered in two options: with individual integrators for the controller’s integral component and the actuator model, and with a common integrator for the controller’s integral component and the actuator model. In the latter option, the signal from the actuator model is subtracted from the controller’s integral component, due to which the possibility of the integrator’s output to reach the integral component’s limit values is ruled out. The versions are compared by analyzing the automatic control system performance in the pulsed actuator’s operation mode based on simulation for the superheated steam temperature control section of a steam boiler equipped with a surface steam desuperheater. The analysis was carried out taking into account both the usual dynamic accuracy indicators and the number of actuators switched into operation during the transient. It is shown that the advantage of the version with the PID algorithm and common integrator for the integral component and the actuator model is that there is no need in this case to calculate the controlled variable second derivative; in addition, this version is free from the problem connected with accumulation of the difference between the signals from the actuator and its model. This version can be considered to be more preferred in implementing a PID algorithm in the software of programmed controllers. Recommendations for self-tuning of pulse duration and the control unit relay element parameters during the control process depending on the algorithm’s individual components are given. By using the proposed recommendations, it becomes possible to achieve an essentially lower actuator switching frequency during the control process.

Multi-Objective Intelligent Optimization of Superheated Steam Temperature Control Based on Cascaded Disturbance Observer

Superheated steam temperature (SST) is one of the most critical parameters for the process safety, overall efficiency and pollution reduction of coal-fired power plants. However, SST control is challenging due to various disturbances and model uncertainties, especially in the face of the growing penetration of intermittent renewable energy into the power grid. To this end, a cascaded Disturbance Observer-PI (DOB-PI) control strategy is proposed to enhance control performance. The observer design and parameter tuning are carried out through mechanism analysis on the proposed structure. Furthermore, a robust loop shaping method is introduced as a hard constraint to balance the control performance and robustness. The controller parameters are optimized based on the multi-objective artificial bee colony optimization (MOABC) algorithm. Simulation results show that the proposed cascaded DOB-PI control strategy can significantly improve the disturbance rejection performance of both the inner- and outer-loops of the SST control system. This paper indicates promising prospects for the proposed method in future applications.

Superheated Steam Temperature Control Based on a Hybrid Active Disturbance Rejection Control

Superheated steam temperature (SST) is a significant index for a coal-fired power plant. Its control is becoming more and more challenging for the reason that the control requirements are stricter and the load command changes extensively and frequently. To deal with the aforementioned challenges, previously the cascade control strategy was usually applied to the control of SST. However, its structure and tuning procedure are complex. To solve this problem, this paper proposes a single-loop control strategy for SST based on a hybrid active disturbance rejection control (ADRC). The stability and ability to reject the secondary disturbance are analyzed theoretically in order to perfect the theory of the hybrid ADRC. Then a tuning procedure is summarized for the hybrid ADRC by analyzing the influences of all parameters on control performance. Using the proposed tuning method, a simulation is carried out illustrating that the hybrid ADRC is able to improve the dynamic performance of SST with good robustness. Eventually, the hybrid ADRC is applied to the SST system of a power plant simulator. Experimental results indicate that the single-loop control strategy based on the hybrid ADRC has better control performance and simpler structure than cascade control strategies. The successful application of the proposed hybrid ADRC shows its promising prospect of field tests in future power industry with the increasing demand on integrating more renewables into the grid.

Controlling the Superheated Steam Temperature during Buffer Consumption of Gaseous Production Waste through Adjusting the Injection and Flame Position

The article considers the possibility of achieving more efficient performance of a TP-13B industrial steam boiler fitted with a spray desuperheater and operating in the mode of buffer consumption of blast-furnace gas as applied to the superheated steam temperature automatic closed-loop control system. The main problem stems from the fact that the superheated steam temperature increases essentially due to large blast-furnace gas flowrates and displacement of the flame when shifting to operation with a large fraction of blast-furnace gas (with respect to the natural gas fraction). The usual injection adjustment range turns out to be insufficient for stabilizing the steam temperature downstream of the second-stage convection steam superheater (CSS2). In addition, the steam temperature downstream of the first-stage convection steam superheater (CSS1) increases significantly, because this section is not protected by injections. For solving the problem, it is proposed to use a combined system, which uses, in addition to the conventional steam temperature controller downstream of the CSS2, which adjusts the injection, a controller of steam temperature downstream of the CSS1, which adjusts the flame position by turning the air-control registers. With the steam temperature downstream of the CSS1 stabilized by adjusting the air-control registers, it becomes possible to pose less demanding requirements to the injections; in addition, with such stabilization, the CSS1 metal is protected from overheating. This is an advantage in comparison with the well-known arrangement in which such control is only performed when the injection valve position approaches the specified limit values. The functional and structural diagrams of the proposed control system are given. The parameters of the plant model channels’ transfer functions are determined proceeding from the known experimental data for the TP-13B boiler. The system has been studied by carrying out computations in the environment of the MathCad software system and the MatLab/Simulink modular simulation software package. The simulation model includes nonlinearities typical for the automation equipment used in thermal power engineering. The effectiveness of the proposed combined control system during operation with essential variations of the blast-furnace gas flowrate has been demonstrated. The information presented in the article can be used in fitting the industrial steam boilers operating with buffer consumption of gaseous production waste with means for automatic control of superheated steam temperature.

Improving Superheated Steam Temperature Control Using United Long Short Term Memory and MPC

Superheated steam temperature is one of the most important process variables for controlling the steam quality of thermal power units. In order to improve the accuracy of superheated steam temperature and the stability of valves for desuperheating water, this paper proposed a novel control strategy called united long short-term memory (LSTM) and model predictive control (MPC), which is weighted by particle swarm optimization. First, a deeply learnt inverse model is made to express the potential nonlinear dynamic characteristics of data and to predict the future valve opening in short-term. Secondly, model predictive control is used to control the secondary superheated steam temperature. Thirdly, the two predicted valve opening are weighted by particle swarm optimization. The combined deep learning inverse model control and MPC can make up the deficiencies of each other, i.e., over fitting of deep learning inverse model and linearity of MPC. The simulation experiments proved the advantage of LSTM-MPC in comparison with traditional PID and single MPC control.

The research of superheated steam temperature control based on generalized predictive control algorithm and adaptive forgetting factor

SummaryThe superheated steam temperature system of the thermal power plant has the characteristics of large inertia, nonlinearity, and strong time variation, which make it difficult to be controlled. To address these problems, this paper proposes a generalized predictive control algorithm with an adaptive forgetting factor. First, based on a fuzzy algorithm and a recursive least squares algorithm, the controlled object's model can be quickly and accurately obtained with the adaptive forgetting factor in real time. It overcomes the nonlinear and time‐varying problems of the controlled object in the control progress. Meanwhile, it also solves the problem of data saturation and the weight assignment of the “new and old” data during online identification. Second, an adaptive generalized predictive controller algorithm has been developed with the controlled object. It solves the large inertia problem of the controlled object. Finally, through establishing simulation model of the superheated steam temperature system and simulating, the results show that the proposed method has better control performance, antidisturbance ability, adaptability, and robustness. Moreover, it has a certain reference significance for the design of a practical control system.

A PSO-Based Recurrent Closed-Loop Optimization Method for Multiple Controller Single-Output Thermal Engineering Systems

For solving the problems of closed-loop optimization on controller parameters of multiple-controller single-output thermal engineering system, this paper proposes a recurrent optimization method that is based on the particle swarm computing and closed-loop simulation (PSO-RCO). It consists of a set of closed-loop identification, simulation, and optimization functions that are organized in a recurrent working flow. The working flow makes one controller tuned at a time whilst others keep their values. It ends after several rounds of overall optimizations. Such a recurrently alternative tuning can greatly speed up the convergence of controller parameters to reasonable values. Verifications on practical data from a superheated steam temperature control system show that the optimized control system performance is greatly improved by reasonable controller parameters and practicable control action. With the advantage of not interfering system operation and the potential supporting on big data identification method, the PSO-RCO is a promising method for control system optimization.

Modeling and modernization of the boiler unit temperature control system

The article considers controlling the temperature of superheated steam in boiler units. When regulating the temperature of steam in modern boilers, special requirements are imposed on the accuracy of maintaining the temperature at a given level. The temperature must be maintained close to the value set in the design of the unit, regardless of the operating conditions of the boiler and its load. With a decrease in temperature, not only the effectivity of the entire installation decreases, but there is also an increase in the probability of emergency situations. An increase in temperature leads to deformation and premature wear of the metal of the boiler, resulting in the boiler emergency stop. The necessity of controlling the temperature of superheated steam in boilers is also relevant owing to the aging of the equipment. These facts make us conclude that the problem of maintaining temperature is one of the most important tasks in the boiler controlling. A review of scientific and information sources on this subject has been presented. As it follows from the above analysis, at present the controlling the temperature of superheated steam has not been fully studied. A mathematical model of the superheated steam temperature control system is presented, it taking into account the non-linearities of the subjects of research. It has been established that the control system responds adequately to disturbances and restores the set temperature of superheated steam, changing the necessary parameters of the system. It is proposed to modernize the temperature control system of the boiler unit by installing a new VariCool desuperheater and vibration control system, which will proactively identify possible malfunctions and partially diagnose the condition of the equipment in real time under operating conditions, without waiting for stops and repairs. A visualization of the system work in Scada- system simulating manual work of a technologist has been fulfilled

Study and Application of Fuzzy PID Intelligent Control

In the boiler automatic control system, there are some characteristics of time-varying, large lag and many disturbances in the process of boiler superheated steam temperature control. The traditional PID control cannot achieve the desired control effect, so an intelligent control algorithm called fuzzy PID control is proposed. Fuzzy PID control is based on the PID algorithm, with the error and error rate as input, using fuzzy rules for fuzzy control. By comparing the PID control algorithm with the fuzzy PID control algorithm in MATLAB simulation, the superiority and feasibility of the fuzzy PID control algorithm are verified.

A Tuning Method of Active Disturbance Rejection Control for a Class of High-Order Processes

This paper aims to propose a quantitative tuning method for active disturbance rejection control (ADRC) that controls the K /( Ts + 1) n -type high-order processes. An asymptote in the Nyquist curve has been observed for the first time and its mathematical expression has been deduced. An asymptote condition is provided in order to derive a parameter tuning rule under the sensitivity constraint. Although this proposed tuning rule is originally designed for a certain type of high-order processes, it can be extended to other types processes that can be approximated into the form of K /( Ts + 1) n . Comparisons with different PID control strategies have been conducted for a range of cases to demonstrate the efficiency of the proposed tuning method. Finally, the effectiveness of the proposed tuning rule is experimentally verified on water tank system that exhibits high-order dynamics. Field tests on the superheater steam temperature control of a circulating fluidized bed power plant further demonstrate its potential for applications in complex industrial processes.

Superheated steam temperature control based on modified active disturbance rejection control

Control of superheated steam temperature (SST) is becoming more and more challenging because of unknown disturbances caused by the frequent and extensive load changes and strict control requirements for the efficiency and safety. This is becoming even severe while the intermittent renewables penetration is growing. To this end, the working principle of SST is depicted and the models of SST are identified from the open-loop step response data. Considering the sluggish responses to the disturbances caused by high order dynamics, a modified active disturbance rejection control (ADRC) is proposed to enhance the control performance. Stability analysis of modified ADRC is derived theoretically to perfect the theory of modified ADRC. Then a practical tuning procedure is summarized for modified ADRC that can be readily understood by field engineers even though it involves trial and error tests. A simulation example shows that modified ADRC can improve the performance of tracking and disturbance rejection simultaneously while maintain a good robustness. A modified ADRC based cascade control strategy is proposed for the SST control system and the control performance is initially confirmed by a simulation based on the identified models. A field application in a 300 MW circulating fluidized bed (CFB) power plant demonstrates the advantages of the proposed strategy, which shows the temperature deviation can be significantly reduced in both the small-scale load varying condition and the large-scale load varying condition. The successful application of the proposed SST control system indicates a promising future of modified ADRC in power industry with the increasing demand on integrating more renewables into the power grid.