The integration of distributed generation into electric power systems requires advanced methods for control under normal, emergency, and post-emergency operating conditions. Distributed generation can rely on asynchronized synchronous generators (ASGs), which have advantages over synchronous machines. Their application however necessitates sophisticated automatic control systems. This study aims to identify the effects of a self-tuning predictive controller designed to control rotor speed of ASGs of the mini hydropower plant operating within the system for power supply to non-traction consumers of alternating current railway. The paper presents a diagram of the simulation model of the power system under study, which encompasses the mini hydropower plant based on ASGs. To improve the quality of electric power, a DC link is used for connection with the railway power system. The developed models of the ASG excitation system and self-tuning predictive speed controller are described. The method for determining the forecasting time is presented along with the modeling results for normal and emergency conditions of the power system at issue. The modeling results have proven the effectiveness of the proposed automatic speed controller, which exhibits the improved indicators of rotor speed and frequency control in the network. In the short-term remote short-circuit mode, compared to conventional automatic speed controllers, the use of the proposed controller allowed: to reduce the transient process time of the ASG rotor speed and network frequency by 33.3 %; to reduce the ASG rotor speed overshoot by 42.1 % and the frequency overshoot by 28.6 %; to improve the damping degree of the ASG rotor speed oscillations by 56 % and the network frequency by 52 %. After disconnecting a long-term remote short-circuit, the transient process time of the rotor speed decreases by 3.8 times, and for the network frequency - by 2.2 times; also, the maximum deviation of the ASG rotor speed decreases by 29 times. For voltage, a slight decrease in the dip in the long-term short-circuit mode can be noted.
This work addresses the challenge of poor wettability and agglomeration of cheap silica (SiO2) particles in aluminum melts, which hinders the production of cost-effective aluminum matrix composites. The aim was to develop a resource-efficient technology for fabricating Al-SiO2 composites using silicon production waste (amorphous microsilica) as a reinforcement. A hypoeutectic AlSi7 alloy was reinforced with 5-wt
Introduction. One of the vibration methods for processing loose finely dispersed mineral raw materials is the separation method on a vibrating surface. Separation occurs according to size, shape of particles, coefficient of friction, elasticity and other mechanical parameters of particles. The efficiency of the separation process depends on the correct choice of technological characteristics of the working equipment. To solve such problems, mechano-rheological models are widely used. The issues of rational construction of research models, based on the specific conditions of the considered dynamic processes, are important and relevant. Materials and methods of research. Identification of rational parameters and modes of operation of vibration equipment is carried out experimentally or by mathematical modeling of the vibration process of the interaction of particles of mineral raw materials with the vibrating body of the separator. Mathematical models are developed for the separated components of the original ore material, which allow studying the dynamics of the movement of particles of the material along the vibrating body of the separator, and as a result of the research, the most rational operating modes of the equipment are determined. Research results and discussion. The presented mechano-rheological system as a model of a material particle is designed to study the processes of interaction with the working body of the separator, a mathematical description of the model is given. The model makes it possible to study the influence of the mechanical properties of the material (elastic, dissipative, plastic) on the dynamics of the process of movement of a material particle along the working body of the separator. For different stages of particle motion, models of different levels of complexity are recommended, which greatly facilitates the solution of problems for the development of algorithms and software for the vibration process under study. This increases the efficiency of the practical application of mathematical models in determining the rational operating modes of the equipment and evaluating the effectiveness of the vibration separation process. Conclusion. To study the process of vibrational separation at various stages of the movement of particles of ore material, it is recommended to use mathematical models of different levels of complexity. A mathematical description of research models for various stages of the vibrational process is presented, the conditions for the transition between the stages of particle motion are given. Resume. Thus, the presented mathematical model makes it possible to study the dynamics of the movement of ore material along the working body of the separator, taking into account the main mechanical properties of the material. The use of the developed recommendations increases the efficiency of the practical application of mechanorheological models for research purposes.
A method of preparing tomographic images of multielectron (molecular) systems is theoretically substantiated. According to the current concepts, spin-spin coupling between resonating nuclei manifested in the NMR spectra is due to the electron motion inside the space of the molecule. Thus, it can be assumed that the interaction-containing space corresponds to the molecule′s size. Modern high-resolution NMR spectrometers allow studying low-energy (<1 Hz) interactions. From the experimental viewpoint, the inherently incorrect J → F(r, θ, φ, E) inverse problem should be solved. At the first stage, points of space occupied by some molecular (multielectron) system can be visualized using spin-spin coupling constants. At the next stage, tomographic images can be obtained from the calculated “exact” wave functions. This requires quite powerful computers and corresponding software programs. We propose a block diagram of a device for implementing a theoretically substantiated fundamentally new method of retrieving information about the spatial structure of substance at the molecular level.
Abstract. The purpose of this work is to evaluate the effect of the outer shell of a rod made using FDM printing on its static strength under central tension. The discrete filling structure of the internal volume of the part is determined by the specifics of the FDM printing. The specified geometry and dimensions of the part are provided by the outer shell. It is not possible to correctly assess the strength of such a part using existing calculation methods. Experimental studies were conducted to achieve this goal. Since thermoplastic materials are used for the manufacture of rods using FDM technology, GOST for tensile testing of plastics was adopted as the basis for selecting the shape and size of samples and conducting tests. With the same percentage of filling of the inner volume of the samples, the thickness parameters of the outer shell changed. According to the test results, it was found that the overall strength of the rod, all other things being equal, is influenced by the proportion of the shell area relative to the nominal cross-sectional area of the sample and the nature of the shell thickness distribution along the contour of the section. The dependencies determining the influence of the parameters of the outer shell of the rod on its strength properties were revealed. The knowledge gained is a prerequisite for the theoretical substantiation of the influence of the parameters of the shell of the FDM rod on its strength.
