Digest of "Invariant Method of Load Independent Pressure Control in Steam Boiler"

The paper considers the possibility of steam production and supply process improvement by perfection of the steam boiler control system, applying invariance principle that makes possible preemptive compensation of the influence of steam expenditure as a disturbance on the control process quality and efficiency. For the development of invariant control system, the mathematical modeling and simulation in MATLAB - SIMULINK environment is made. The control unit is low pressure steam boiler with one input impact to control - the heat flow of burning gas mixture fuel, one measured output parameter of the process - the steam pressure, and the main disturbance as a load impact - the steam expenditure. The mathematical and virtual models and block-diagrams for transient process simulation is compiled, allowing to start practical design and investigation of steam boiler invariant control system with high operation stability under essentially fluctuating load. The simulation results prove that the optimal solution for the transient process improvement in steam boiler, taking in account fluctuating load, is invariant PID-DPC two loop control system with disturbance impact on steam pressure preemptive compensation. Under invariant control the steam pressure overshoots decreases substantially in comparison with the traditional PID-feedback control method

ENGINEERING FOR RURAL DEVELOPMENT DESIGN AND VERIFICATION OF VERTICAL AXIS WIND TURBINE SIMULATION MODEL

Abstract. In the course of this research the vertical axis wind turbine simulation model has been designed and verified using the MATLAB SIMULINK tool for transient process simulation. The research was based on the study of the real vertical axis wind turbine, which provided the basis for building the mathematical model. The mathematical model includes the mechanical model of the turbine, wind, turbine rotor, power output and all rotation parameter analysis and calculations. The main goal of the research was achieved and the designed model was successfully verified by the real turbine performance data. The results showed that the error of the modelled data and the real turbine data is less that 2 %, which provides an opportunity to use this model for subsequent research and turbine production or R&D in the future. Introduction Use of the renewable power resources has been the subject of active discussions and research for many years already. Exorbitant amounts have been invested to research this area aiming to find the possibility to gain high quality power from renewable energy resources (biomass, sun, wind) with a high degree of efficiency. Optimisation of the performance factor in energy generation and use remains a compelling and as yet unresolved issue in modern power production systems, the same being true for the renewable power industry The most important role in speeding-up the progress in the development of the new technologies belongs to computer model based engineering of equipment and process simulation, which provides an opportunity to test the new ideas, methods and strategic solutions and to obtain quick and accurate results without the necessity to spend considerable amounts on acquisition and installation of experimental equipment If we take wind power engineering -any system here is pretty complicated for the set of its parameters being described merely by means of simple algebraic equation, which suggests that the only way how to simulate the processes occurring within the system and analyse the obtained results both in digital and graphical format is to apply the real-time simulation method By analysing the exploratory work done in the area of simulation of mechanical stages of a wind station -blades, rotor, reducer, it may be concluded that in the majority of cases the simulation models of that stage are being simplified, which gives a generalised representation of the wind energy transformation process patterns while a lot of important aspects are disregarded and, as a result, the model fails to properly reflect the actual processes. The present research improves the traditional models by assessing the parameters determinative for dynamic transformation processes in wind turbine operatio

Adaptive Model of Wastewater Aeration Tank

Abstract – The paper discusses the methodology of oxygen transfer virtual simulation in a wastewater biological treatment process, using the MATLAB/SIMULINK technology. A self-tuning adaptive model of a wastewater aeration tank, as a non-stationary object, with variable time dependent sensitivity and inertia indexes, as the functions of input variable - air pneumatic supply capacity Lg(t) (m3/min), output variable – dissolved oxygen concentration C(t) (g/m3) and oxygen expenditure, as a load – q(t) (g/min), required for wastewater complete purification, is expounded. Virtual models, applying Laplace transforms and SIMULINK blocks library, are composed in order to compare the transient processes of dissolved oxygen concentration in the simplified stationary model with constant sensitivity and inertia coefficients, and in the non-stationary model with variable sensitivity and inertia indexes. The simulation block-diagram for non-stationary model adoption to the variable parameters is developed, using informative links from input variable Lg(t), from variable load q(t) and feedback from output variable C(t) as inputs of calculation modulus, allowing to instantly re-calculate the variable indexes during simulation time. Comparison of the simplified stationary model and the non-stationary model shows that the simulation results of oxygen transfer differ up to 50%

ENGINEERING FOR RURAL DEVELOPMENT NON-STATIONARY HEATING OF LOW-POWER INDUCTION MOTOR UNDER CONTINUED OVERLOAD

Abstract. The paper discusses transient heating processes and the response of a low-power induction motor to permanent constant load, overload and a locked rotor under a standard electrical supply system (380V, 50 Hz) for cold initial conditions and constant ambient temperature. The experimental investigations are performed on a 1.1 kW totally enclosed fan-cooled three-phase induction motor. The transient temperatures are measured in 6 points of the stator end windings and in 2 points of the motor casing using thermocouples, current sensors and loggers for data processing and archiving. The resistive stator losses for single-phase are calculated using the stator windings equivalent parameters, considering the dynamic change of the stator current and the windings resistance from temperature. The experimental tests and analytical calculations show that the stator windings heating curves obey the first order non-stationary thermal process with time dependent thermal capacity and heat dissipation factor, as the functions of the motor part temperature. Analyses of the study results show, that an adaptive self-tuning virtual model of the induction motor thermal process should be composed for adequate programming of the processor-based motor protective devices to improve their operation quality. Key words: induction motor, current, losses, heating temperature, continued overload, thermal model. Introduction Low voltage induction motors (400 V, 50 Hz) have got large applications in industry and agriculture, consuming the majority of the total electrical energy consumption in the world. They are available in a wide choice, as from several tens watts up to several hundreds kilowatts. Typical induction motor (IM) applications in rural industry include pumps, fans, compressors, mills, saw machines, cranes, conveyors, crushers, etc. The statistics have shown that despite the IM high reliability and simplicity of construction, the annual motor failure rate is conservatively estimated at 3-5 % per year, and in extreme cases, up to 12 % [1]. IM failures cause essential direct and technological losses involving the motor replacement and repair, as well as interruption of the production process. IM failures may be classified as follows: 1) electrical related failures ~35 %; 2) mechanical related failures ~31 %; 3) environmental impact and other reasons related failures ~34 % [1]. Analyses of the IM failure reasons show that many of them are caused by prolonged heating of the different parts involved in IM operation. That is why an accurate tracking of the IM thermal status and adequate response of the protection system to thermal overloads is very important. Modern trends in electric motor construction are to make IM more compact and efficient. At the same time the new IM are more sensitive to mechanical and electrical overloads. On the other hand, overestimation of the thermal state of the induction motor can cause undesirable IM stoppage and useless interruption of the production process. Therefore, it is very important to predict the thermal condition of the induction motor and to develop a desirable accurate and flexible thermal model of IM operation under prolonged overload. A detailed description of experimental and analytical research methods and results of the transient heating of IM parts and thermal modelling is given in The most sensitive part of IM to thermal overloads is stator windings. The main limiting factor of IM continuously loading is the stator winding temperature. Exceeding the temperature limit, results in acceleration of the oxidation process in the insulation materials what eventually leads to IM damage. Commonly for the heating process of the IM stator windings the first-order thermal model with constant parameter

Invariant Method of Load Independent Pressure Control in Steam Boiler

The paper considers the possibility of steam production and supply process improvement by perfection of the steam boiler control system, applying invariance principle that makes possible preemptive compensation of the influence of steam expenditure as a disturbance on the control process quality and efficiency. For the development of invariant control system, the mathematical modeling and simulation in MATLABSIMULINK environment is made. The control unit is low pressure steam boiler with one input impact to control – the heat flow of burning gas mixture fuel, one measured output parameter of the process – the steam pressure, and the main disturbance as a load impact – the steam expenditure. The mathematical and virtual models and block-diagrams for transient process simulation is compiled, allowing to start practical design and investigation of steam boiler invariant control system with high operation stability under essentially fluctuating load. The simulation results prove that the optimal solution for the transient process improvement in steam boiler, taking in account fluctuating load, is invariant PID-DPC two loop control system with disturbance impact on steam pressure preemptive compensation. Under invariant control the steam pressure overshoots decreases substantially in comparison with the traditional PID-feedback control method

Narrow and variable lines in the ultraviolet spectrum of the Seyfert galaxy NGC4151

The Seyfert galaxy NGC4151 observed when the nucleus is at a minimum has two emission lines of full width at half maximum less than 7 and 16 A, respectively, and varying in intensity by a factor of three in 10 days. These lines are too narrow to be emitted by the whole broad-line region and must arise instead from two localized regions which have a special excitation mechanism, possibly a two-sided jet

Modernas tehnologijas energijas ieguvei un efektivai izmantosanai Starptautiska zinatniska konference. Rakstu krajums

Abstracts in EnglishAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELatvian Electric Power Company " Latvenergo" , Riga (Latvia); Latvian Electric Power Engineering Society, Riga (Latvia); Power Company " Jauda" , Riga (Latvia); Latvian Council of Science, Riga (Latvia); Ministry of Agriculture of the Republic of Latvia, Riga (Latvia). Rural Development Dept.LVLatvi