Bohumil Šulc

Power System and Power Plant Dynamic Simulation

Abstract The scale and complexity of the present power systems are increasing. To simulate such a system, it is necessary to model both the transmission grid and the power plant in detail. This paper presents the connection of the network simulator program MODES with the detailed model of the steam boiler. The power plant model consists of a boiler island model and turboalternator island model. It is a linearized model of the pulverized fuel fired drum steam boiler. This model is developed in standard simulation program. Examples of an island operation and auxiliary transients computation illustrate the use for power system analysis.

Advanced Modelling and Control using a Laboratory Plant with Hybrid Processes

Abstract Advanced control theory is usually associated with the use of abstract mathematical tools. It requires much time and a good theoretical background to understand and explain these tools. In ordinary university courses or in continuing professional education organized by employers, it is not easy to meet these requirements. Widely used system simulation and virtual experiments can be a good aid to increase clarity, but they cannot fully demonstrate the problems that a control designer or user may encounter in practical implementation. A laboratory scale plant has been designed for this purpose in the framework of research activities focused on hybrid systems. It exhibits most of the hybrid phenomena typical of process control applications. The plant is also equipped with industrial control hardware, so that educational (as well as research) experiments can be carried out implementing advanced hybrid control algorithms in conditions close to real world applications. The instrumentation provides a remote web access facility. A mathematical and technical description of the pilot plant is included here, and this will enable readers to consider whether a similar device could be useful for their own educational and/or research purposes. Some examples of experimental results are also given.

Control for ecological improvement of small biomass boilers

Abstract The aim of this paper is to present various types of research on reducing emissions in the flue gases produced by low-power biomass boilers, especially when the boilers operate outside their nominal operating regime. This long-term investigation program is being carried out on a pilot boiler in the university laboratories. The program involves acquiring additional instrumentation for performing and evaluating present and future experiments, creating various types of models of the boiler for designing and testing the control algorithms using available data, and implementing and evaluating the algorithms in real operation. The pilot device enables us to experiment using non-standard instrumentation, but throughout our research it is necessary to strike a balance between ecological policy requirements and economic considerations.

Transfer Issues of Control Optimizing Combustion from Small-scale to Medium-scale Biomass-fired Boilers

Abstract The quick development of biomass fired boilers increased the attention being paid to the ecological and economical aspects of their operation. A very important role in the process of adapting to harder regulations has been the control technology replacing older simple solutions. Lately, we have been offered a very interesting opportunity to make use of our experience with small-scale boiler control which has been gradually equipped with instruments for more sophisticated experiments and to transfer verified control algorithms to a district heating boiler of medium-scale size. The following text describes what has been achieved in experiments with the small-scale boiler and how this can be transferred to bigger scale one. An algorithm to optimize the combustion process from the efficiency point of view, as well as harmful emission reduction is described in detail.

Continuous Control Issues Concerning Operation Improvement of Small-Scale Biomass Boilers

Abstract To meet the increasing environmental and efficiency requirements, the possibilities to improve the performance of a 25 kWth wood pellet boiler by utilizing PLC and feedback control are investigated. The process is first stabilized by improving the grate sweeping sequence, which originally disturbs the process. Prior to continuous combustion control development, the process is analyzed and identified. After sequential control improvements the combustion behaves well but tends to drift. A PID controller was designed to enable drifting compensation. It is shown that improved grate sweeping sequence and continuous feedback control provide a major improvement for system performance cost effectively.

Evaluation of open-loop frequency indicators in a closed loop for PID controller autotuning

In industrial practice, PID controllers are extensively used because they can be successfully implemented without knowing a model of the object or process which is controlled. Despite of the fact that many PID controller tuning algorithms have been developed since the Ziegler and Nichols tuning procedures were published in 1942, their experimental method continues to be used up to now. There are two main reasons why newer methods are not widely-used: the methods are based on a model of the controlled plant, and/or it is necessary to stop the control process during controller retuning. Our method presented in this paper is based on an experimentally performed evaluation of excited frequency responses with the aim of achieving recommended values of one or more control quality indicators known from the course of the Nyquist plot, e.g. Frequency response evaluation can be performed in a closed loop with no controller function degradation, and no model is necessary for frequency response evaluation. In this way, the main problems of other tuning methods are eliminated. Since there is no need for a model, the tuning method can be used in a control loop involving nonlinearities even in the controller.

Engineering Models of a Coal Fired Steam Boiler in Teaching, Training and Research Applications

Abstract Nowadays, engineering models used in training and learning simulators have become an integral part in the preparation of power plant operators and in postgraduate courses. This paper provides a survey of major applications of an engineering model developed by the authors for engineering simulation and advanced control of processes in power units with coal-fired steam boilers. The model was developed in the MATLAB-SIMULINK simulation package allowing not only educational applications but even connection to industrial control systems.

Engineering Simulator of Coal Fired Steam Boiler Applied to Optimum Combustion Control

Abstract The paper presents an update of a coal fired steam boiler model and particularly describes a way and some possibilities how to work with the standard simulation program SIMULINK-MATLAB when these tools are used in preparation of an engineering simulator. This model is a linearized model of a real drum pulverized-coal fired steam boiler. The model is a basis for development of the Steam Drum Boiler Engineering Simulator. Besides the use of conventional PID controllers, the extremal controller is tested for Optimum Combustion Control with the aim to reduce amount of harmful emissions by controlling the primary air flow.

Neural Network Evaluation of Combustion Process for Continuous Control of Small Scale Biomass Fired Boilers

Abstract Boilers based on combustion of biomass become widely used as a heating source nowadays. The modern ones are typically controlled automatically. The control algorithm of those boilers is crucial in reaching optimal operational conditions by means of maximal efficiency and minimal environmental impact. On the other hand, the acquisition costs of these advanced devices should be maintained at reasonable level. This paper deals with implementation of modern proper control algorithm and obtaining the necessary input values that cannot be easily measured operationally by a direct measurement.

Harmonie excitation based autotuning: Autotuning usable for controlling biomass combustion processes

Controlling combustion processes is an important task, mainly with respect to energy efficiency and ecological impacts. This problem has become significant with the increased use of biomass-fired boilers, including low-power boilers. The combustion process is a process that we have limited information about. The equations for the chemical reactions are known, but in reality combustion of biomass is much more complicated and more variable than a mathematical model can express. It is therefore not simple to design a controller that is able to control the combustion process effectively in the whole range. Small-scale biomass-fired boilers are usually equipped with simple two-state (on/off) controllers. Many laboratories have attempted to develop a model of the combustion process suitable for controller setting and parameter adaptation, but the results are not yet satisfactory or generally valid. Thus, advanced model-based control strategies are not usable, while the use of a model-free controller is not excluded if well-designed tuning rules can be provided. An approach which tries to satisfy most of the requirements of industrial practice is presented in this paper, which is based on an experimentally performed evaluation of small amplitude excited frequency responses with the aim to achieve recommended values of one or more control quality indicator known e.g. from the course of the Nyquist plot. The indicators can be evaluated experimentally in control loops involving nonlinearities. In this sense, the method has a philosophy similar to that of the popular Ziegler and Nichols method, but no interruption of the control process is necessary and the amplitude of the excited oscillation can be set by operator. The main advantages of the method presented here are: there is no use of any mathematical model, it can be used as an addition to the existing controller purely by software, and there is no need to interrupt the control process while retuning the controller.