The application of a new PID autotuning method for the steam/water loop in large scale ships

In large scale ships, the most used controllers for the steam/water loop are still the proportional-integral-derivative (PID) controllers. However, the tuning rules for the PID parameters are based on empirical knowledge and the performance for the loops is not satisfying. In order to improve the control performance of the steam/water loop, the application of a recently developed PID autotuning method is studied. Firstly, a 'forbidden region' on the Nyquist plane can be obtained based on user-defined performance requirements such as robustness or gain margin and phase margin. Secondly, the dynamic of the system can be obtained with a sine test around the operation point. Finally, the PID controller's parameters can be obtained by locating the frequency response of the controlled system at the edge of the 'forbidden region'. To verify the effectiveness of the new PID autotuning method, comparisons are presented with other PID autotuning methods, as well as the model predictive control. The results show the superiority of the new PID autotuning method

One approach to temperature distribution control in thermal power plant boilers

Optimization of the combustion control process in a tangentially fired pulverized coal boiler, to achieve uniform temperature distribution, is discussed in the paper. This issue is even more critical in those thermal power plants which are not equipped with modern systems for combustion enhancement, such as low NOx burners. Research has shown that the temperature distribution inside the boiler of such power plant can be controlled by adjusting firing, through coal redistribution among the mills. Furthermore, disturbed flame symmetry (i.e. non-uniform temperature distribution in the boiler) is reflected in a large difference between the output temperatures measured on the left and right sides of the boiler. Given the non-stationary conditions typical of thermal power plant boilers, an adaptive control approach is proposed, based on PI controllers which are very popular in industry and widely accepted. Self-tuning of the PI controllers is based on dynamic model parameters derived applying the weighted recursive least squares (WRLS) method to real data recorded at Nikola Tesla B thermal power plant in Serbia, whose nominal power is 650 MW. The same model was later used to test the proposed control approach

The potential of fractional order distributed MPC applied to steam/water loop in large scale ships

The steam/water loop is a crucial part of a steam power plant. However, satisfying control performance is difficult to obtain due to the frequent disturbance and load fluctuation. A fractional order model predictive control was studied in this paper to improve the control performance of the steam/water loop. Firstly, the dynamic of the steam/water loop was introduced in large-scale ships. Then, the model predictive control with an extended prediction self adaptive controller framework was designed for the steam/water loop with a distributed scheme. Instead of an integer cost function, a fractional order cost function was applied in the model predictive control optimization step. The superiority of the fractional order model predictive control was validated with reference tracking and load fluctuation experiments

Neural Network Based PI Controller Parameter Calculation on a Boiler Drum Level System

AbstractThe controller parameters influence the performance of the closed loop system. So we have to develop a tuning method for obtaining the optimum values of the controller parameters with respect to a particular process. Controller tuning is very much process dependent and any improper selection of the controller settings may lead to instability and affect performance of the closed loop system. Closed loop tuning methods like Ziegler-Nichols method depends on estimation of ultimate gain and ultimate time period. When trying different gains on an unknown process the amplitude of undampened oscillations can become unsafe or on the conversely for low initial gain settings the test can take a long time to reach sustained oscillation condition. This paper proposes a neural network based scheme to estimate ultimate gain and optimum proportional and integral value of PI controller within affordable time limit and safe input range when the parameters change

Internet based data logging and supervisory control of boiler drum level using LabVIEW

This work describes a framework of a Internet based data logging and supervisory control of boiler drum level system. The design and implementation of this process is done by the LabVIEW software. The data of the process variables (Temperature and Level) from the boiler system need to be logged in a database for further analysis and supervisory control. A LabVIEW based data logging and supervisory control program simulates the process and the generated data are logged in to the database as text file with proper indication about the status of the process variable (normal or not normal. Three different types of boiler drum level control system are designed in the Circuit Design and Simulation toolkit of LabVIEW. This work provides the knowledge about the Fuzzy Adaptive PID Controller and the various PID controller design methods such as Zeigler-Nichol method, Tyreus-Luyben method, Internal Model Control (IMC). Comparative study is made on the performance of the PID and Fuzzy Adaptive PID controller for better control system design. The internet plays a significant and vital role in the real time control and monitoring of the industrial process. Internet based system control and monitor the plant system remotely from anywhere without any limitation to any geographical region. Internet based boiler control system is developed by a Web Publishing tool in LabVIEW. The use of internet as a communication medium provides the flexible and cost- effective solution. Now, to analyse the performance of boiler drum level control system, Internet based data logging and supervisory control system is designed. Hence, anyone can control and monitor the boiler plant globally

Distributed model predictive control of steam/water loop in large scale ships

In modern steam power plants, the ever-increasing complexity requires great reliability and flexibility of the control system. Hence, in this paper, the feasibility of a distributed model predictive control (DiMPC) strategy with an extended prediction self-adaptive control (EPSAC) framework is studied, in which the multiple controllers allow each sub-loop to have its own requirement flexibility. Meanwhile, the model predictive control can guarantee a good performance for the system with constraints. The performance is compared against a decentralized model predictive control (DeMPC) and a centralized model predictive control (CMPC). In order to improve the computing speed, a multiple objective model predictive control (MOMPC) is proposed. For the stability of the control system, the convergence of the DiMPC is discussed. Simulation tests are performed on the five different sub-loops of steam/water loop. The results indicate that the DiMPC may achieve similar performance as CMPC while outperforming the DeMPC method

Control of milk pasteurization process using model predictive approach

YesA milk pasteurization process, a nonlinear process and multivariable interacting system, is difficult to control by the conventional on-off controllers since the on-off controller can handled the temperature profiles for milk and water oscillating over the plant requirements. The multi-variable control approach with model predictive control (MPC) is proposed in this study. The proposed algorithm was tested for control of a milk pasteurization process in three cases of simulation such as set point tracking, model mismatch, difference control and prediction horizons, and time sample. The results for the proposed algorithm show the well performance in keeping both the milk and water temperatures at the desired set points without any oscillation and overshoot and giving less drastic control action compared to the cascade generic model control (GMC) strategy

A Fuzzy Logic-based Tuning Approach of PID Control for Steam Turbines for Solar Applications

Abstract This work aims at improving the control concept based on PID controller by jointly exploiting experience and knowledge on the system behaviour and artificial intelligence. A Concentrated Solar Power Plant (CSPP) system has been modelled and a stability and performance analysis has been carried out, focusing on power control loop, which is normally based on standard PID. A hybrid fuzzy PID approach is proposed to improve the steam turbine governor action and its performance are compared to the classical PID tuned according to three different approaches. Compared to the classic PID, the PID fuzzy logic controller extends the simplicity of PID and adapts the control action at actual operating condition by providing the system with a sort of "decision-making skill". The possibility to design implementable algorithms on PLC, which have stringent computational speed and memory requirements, has been explicitly taken into account in the developed work