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

Improved control and monitor two different PLC using LabVIEW and NI-OPC server

This paper proposes an improved control and monitors between two different PLCs, the Mitsubishi, and Omron. The main advantage is interoperability and communication between both PLC. The use of NI OPC server as the software interface reached interoperability and communication. There were developed two field applications to test interoperability. Laboratory virtual instrument engineering workbench (LabVIEW) uses as the software application for creating the user interface to control and monitor. This improvement show OPC server technology solves data compatibility issue between different driver controller’s and reducing development cost. Regardless of whether there are more than two different PLCs, it's enough to use the NI OPC server. So the benefit of the NI OPC server is not limited to two types of PLC used right now but can also use the other manufacturers. Besides, the improvement of the previous study is the use of the LabVIEW makes data from the OPC server displayed more realistic. The use of LabVIEW allows additional monitoring functions, one of which is LabVIEW vision. Data utilization becomes more flexible, and so it can use for more complex purposes. It is envisaged that this is very useful for Integrator engineer to implement this method in industrial automatio

Implementation of self-tuning control for turbine generators

PhD ThesisThis thesis documents the work that has been done towards the development of a 'practical' self-tuning controller for turbine generator plant. It has been shown by simulation studies and practical investigations using a micro-alternator system that a significant enhancement in the overall performance in terms of control and stability can be achieved by improving the primary controls of a turbine generator using self-tuning control. The self-tuning AVR is based on the Generalised Predictive Control strategy. The design of the controller has been done using standard off-the-shelf microprocessor hardware and structured software design techniques. The proposed design is thus flexible, cost-effective, and readily applicable to 'real' generating plant. Several practical issues have been tackled during the design of the self-tuning controller and techniques to improve the robustness of the measurement system, controller, and parameter estimator have been proposed and evaluated. A simple and robust measurement system for plant variables based on software techniques has been developed and its suitability for use in the self-tuning controller has been practically verified. The convergence, adaptability, and robustness aspects of the parameter estimator have been evaluated and shown to be suitable for long-term operation in 'real' self-tuning controllers. The self-tuning AVR has been extensively evaluated under normal and fault conditions of the turbine generator. It has been shown that this new controller is superior in performance when compared with a conventional lag-lead type of fixed-parameter digital AVR. The use of electrical power as a supplementary feedback signal in the new AVR is shown to further improve the dynamic stability of the system. The self-tuning AVR has been extended to a multivariable integrated self-tuning controller which combines the AVR and EHG functions. The flexibility of the new AVR to enable its expansion for more complex control applications has thus been demonstrated. Simple techniques to incorporate constraints on control inputs without upsetting the loop decoupling property of the multivariable controller have been proposed and evaluated. It is shown that a further improvement in control performance and stability can be achieved by the integrated controller.Parsons Turbine Generators Ltd

The development of boiler control models for the optimization of boiler efficiency

With Eskom’s fleet rapidly reaching end of life and maintenance outages becoming more frequent, it has become more critical to be able to determine transient effects of auxiliary losses and system responses due to instabilities. A low mono-nitrogen oxide (low-NOx) burner replacement project has recently been completed at Camden power station in Ermelo. It has thus deemed itself as a perfect candidate for a model which can be used to understand the new systems’ response during transient scenarios. The aim is to develop a boiler control model to be used for simulation of various process conditions and failure scenarios in order to predict the boiler plants’ behaviour and improve its availability. Research was done on common boiler control practices and modelling of boiler control. A theoretical boiler control model was developed based on the Camden power station’s control system specification. The computational model of the boiler control was implemented in Flownex® simulation environment, which was found to be particular useful for modelling industrial applications. A number of simulations with the computational model were performed and the results were compared against the historic plant data showing good correlation. In parallel, a thermo-fluid model of the boiler was developed using Flownex® by a Masters student at the University of Cape Town, which was then integrated with the control model. The combined Flownex model was used for simulation of the following important cases: a mill trip, a Forced Draught fan trip and load changes. The obtained results show good correlation with the real plant data, indicating that the developed computational model can be considered accurate for Camden’s particular type of boiler and its control. Hence, it is envisaged that the developed combined Flownex model can be applied for simulation of the boilers of the Camden power station

Performance Analysis of Model Predictive Control For Distillation Column

Model predictive control is an advanced process control method. It is a popular technique in chemical plants and oil refineries. Model predictive controller depends on dynamic model of the process and predicts the future output and so that the present input is optimized to avoid the future error. An optimization problem is solved over a prediction horizon P by regulating M control moves .Dynamic matrix control is a popular MPC method and it relies on the state space model of the plant. In this work, first we represent the DMC as an LTI system. The effect of tuning parameter on both first order and second order system is observed by calculating transient parameters like settling time, rise time, peak over shoot. Then the close loop poles are calculated for a specific FOPDT by varying different tuning parameters using the DMC algorithm. From the observation, effect of tuning parameters like P, M, w, N are summarized and a design rule for the parameter adjustment of DMC is proposed. Next a brief study on distillation column is provided and a mathematical model is also discussed. The design rule and control strategy of distillation column are discussed. The control of a distillation column by PID controller is performed for different tuning methods. In order to get stable response decoupling technique is used. Two different techniques like inverted and simplified decoupling are performed and a comparison between them is given by calculating transient parameters. The control of a distillation column by the MPC is also performed. A comparison between two controllers (PID and MPC) is discussed. The features of MPC like constraint handling, disturbance rejection, set point tracking is observed. Here different distillation process is taken and its response after using an MPC controller is observed. MATLAB (matrix laboratory) provides a numerical environment and fourth generation programming language. It provides matrix manipulation, plotting of function, data and implementation of algorithms. It provides a different tool box and Simulink models for process control and design.Model predictive control tool box provides functions, Simulink block for analysing, designing and simulating model predictive control. Here user can provide control and prediction horizon, weighting factor and model length. The toolbox can guide the user regarding tuning parameters and it also facilitates softening of constraints