Lukas Hubka

Calculation of robust PID-controller

This paper deals with a new approach to PID-controller parameter design that is based on the localization method. It is shown that controllers calculated by this method provide possibility to control system with non-linear and non-stationary plant. This paper includes numerical experiments with a set of linearized model of the super-heater. The main result is the methodology for parameter calculation.

Modeling and predictive control of a nonlinear power plant reheater with switched dynamics

This paper is focused on modeling and predictive control of a power plant reheater. The motivation for this research is the necessity to achieve tighter power plant control in the wide range load following operation. The reheater under consideration consists of a series of three heat exchangers and two of them can be fully or partially bypassed. Accurate first principles model of the reheater is developed in the first part of the paper. Good approximation of the distributed parameter behavior is obtained by dividing the dynamics of the individual heat exchangers into several control volumes. Resulting high order model is considerably nonlinear. Moreover, switching of its dynamic behavior occurs because of the bypassing of the individual reheat stages. Thus, this reheater represents a non-trivial control challenge. Model predictive controller is designed in the second part. It is based on a piecewise affine model. Piecewise affine model is used both to approximate reheater nonlinearity and to describe the switches of reheater dynamics. The performance of the predictive controller is compared with the classical control system. Considerable performance improvement can be observed.

Cogeneration units simulation models library

This paper focuses on cogeneration units (Combined Heat and Power (CHP) plants), especially on simulation models of these units or their main parts. The combined production of heat and electricity seems to be a good option for a future market. Cogeneration has fewer losses than traditional production, but on the other hand there are some consumption criteria that must be met. The result of this paper is a software library of the significant parts of CHP plants of different types. Firstly there are short introductions to the two main types of units used for low output power (up to approximately 100 kW) - the gas/biogas/diesel/biodiesel engine and gas (micro-)turbine. The next section describes the basic physical and mathematical relations and the final section presents some results.

Steam turbine and steam reheating simulation model

This paper describes a possible way to build a simulation model of the most important part of a power plant - the turbine with reheating section. The turbine is a key part of the power plant that allows the conversion of the heat energy to electricity via mechanical energy. The paper describes the usual construction of the steam reheater and the turbine connection. The mathematical analysis for all parts, that is, for all the units of the steam reheater, is presented in the form of ordinary differential equations. The turbine simulation model is based on real process measurements and uses the ARX model. Finally some verification results are presented.

Nonlinear model predictive control of the steam superheating - unmeasured disturbance suppression

This paper deals with the nonlinear model predictive control of the superheated steam temperature in the power plant once-through boiler. Particularly the controller response on impulse of unmeasured disturbance in the form of flue gas heat is investigated. The two different nonlinear predictive controllers are described in the paper. The feedback of the first controller is closed by nonlinear open loop observer with correction for offset free reference tracking. The second controller works with the close loop state and unmeasured disturbance observer based on the nonlinear moving horizon algorithm. Responses of these two controllers and response of the original controller based on the adaptive PID are compared.

STATE MODEL OF STEAM REHEATING FOR CONTROL OPTIMIZATION

Abstract This paper presents a nonlinear state space model for thermal process of steam reheating. The purpose of the model is to examine existing control system and to support the development of new more efficient control systems for steam reheating units. This model describes countercurrent heat exchanger (biflux) with bypass and two parallel flow heat exchangers with bypasses and spray attemperator. The model includes interconnections of subsystems and the dynamics of all control valves. The model is a state model which enables modeling of power variation from start up to shut down. First, the basic principles of this approach are compared with already published results. Second, the model is calibrated for the newly designed reheating unit for the planned upgrade of a power plant. Both results from static and dynamic characteristic responses, as well as selected control responses in operating range are presented.

Power plant steam superheater control system preliminary results and experiences from the field tests

This paper describes a newly developed steam superheater control system and its integration into the real power plant control system. The developed control system is based on the principles of the model predictive control. It is intended to replace one part of the existing classical control system that is based on gain scheduled PID controllers. The paper starts with a short description of the controlled plant and then it continues with the description of the predictive controller and its integration into the structure of the existing control system. The main focus is on the results of the functionality tests. The preliminary results hitherto achieved demonstrate the capability of the developed control system and its application potential. However, at the same time, they also show that extensive simulation testing of a controller for such a complex system does not necessarily guarantee perfect control performance and several modifications of the controller will be needed to make it really applicable.

Tram simulation model for energy balance analyses

This paper describes a mathematical model of a tramcar which allows to simulate traffic on any tram track and allows to analyze energetic balance on the electrical power link without real energetic data measurement. The described mathematical model could be a useful tool for the design of an energy recovery system for a real tram track. A short description of the tram track model in the city of Liberec is presented together with the mathematical model of the tramcar type T3.PLF that operates on mentioned track. The model simulation results are confronted with data measured during the real tram operation.

Steam superheaters predictive control system: An implementation Stulukas.hubdy

This paper describes one of the realization possibility of model predictive control algorithm for industry application. In this case, the predictive control strategy should be finally applied on the steam superheaters. It describes the steam superheating technology, the actual state and the vision how to realize the improvement in the control. The detailed description of the software/hardware realization is included. Some significant simulation results from simulation tests and from the real time tests are presented.

Nonlinear process control — once-through boiler

This paper presents the nonlinear control system design algorithm - the localization method - applied to the output superheater of the coal power plant once-through boiler. Theoretical basics of the localization method are shown. Linear and nonlinear models of the superheater were earlier developed. Basic descriptions of these models properties are presented, too. The control of the plant is processed by two control cascades; each of these cascades uses the localization controller and the special element for derivatives evaluating the differentiating filter. Through the research there were the different localization loop configuration developments. Simulation results for these variants of the localization loops are presented.