PNRPU Bulletin. Electrotechnics, Informational Technologies, Control Systems

In connection with the development of the industrial complex, the development of new technologies, the increase in the extraction and processing of natural resources, as well as the study of new territories, there is a widespread use of a controlled electric drive and various types of electric energy converters in the world electric power industry, as well as a steady growth trend in their installed power. For these reasons, the issues of electromagnetic compatibility of the load with the supply network and ensuring the required quality of the converted electricity are particularly acute. A decrease in the quality of the converted electricity leads to a deterioration in energy performance, a decrease in productivity, a reduction in the life of electrical equipment, as well as an increase in the likelihood of an emergency. One of the effective ways to solve this problem is to use a cascade frequency converter, which allows the synthesis of high quality output voltage. Purpose: the development of circuit solutions and control algorithms for a cascade frequency converter that will allow the synthesis of high quality output voltage. Methods: on the basis of number-theoretic methods, theoretical foundations of electrical engineering, fundamentals of power electronics and positional number system, the study of options and ways to increase the possible number of levels of instantly synthesized voltage at the output of a cascade frequency converter was carried out. Results: proposed circuit solutions and control algorithms for a cascade frequency converter, which will improve the quality of the synthesized voltage. A mathematical description of the control algorithms of the unit cells of the cascade frequency converter, allowing to synthesize the required voltage. A quantitative and qualitative comparison of ways to improve the quality of the synthesized voltage at the output of a cascade frequency converter is presented, a histogram of the dependence of the number of synthesized voltage levels on the unit cell construction scheme, the number of cells and control algorithms is shown. The result of mathematical modeling of the phase voltage at the output of a cascade frequency converter synthesized using three two-level cells with differentiated supply voltage and control algorithms with summation and difference of cell voltages in phase is presented. Practical relevance: the proposed schemes and methods for improving the quality of the synthesized voltage at the output of the cascade frequency converter and the results of the studies can be used in the design and development of electric power converters with high quality output voltage. This allows you to increase energy efficiency and significantly improve the harmonic composition of the synthesized voltage.

Currently, research is actively ongoing in the field of quantum computing, quantum computers. Most likely, quantum computers, as it was already in the history of science many times, is not a panacea, but will occupy its niche on a par with conventional calculators. Moreover, in this area there are some features that can be used in binary logic. We are talking about the so-called reversible calculations and special elements, for example, Fredkin’s elements. Purpose: development of a methodology for studying billiard logic circuits in practical classes, development of thedevelopment of a decoder and a memory element, Fredkin element for use in laboratory classes. Methods: The analysis of the billiard full adder, the synthesis of thedecoder and a memory element, Fredkin element based on the LUT FPGA. Results: The study tested in detail the steps of an example of such calculations and offers an element for their implementation in binary logic.Thecircuit operation of the “forward” and “backward” using the symbols of “billiard” balls is analyzed.Decoder and memory element developed,Fredkin element based on the LUT FPGA. Running simulation in NI Multisim, the system of the company National Instruments Electronics Workbench Group circuit simulation, confirming the workability of the proposed gate. Practical relevance:a technique for studying billiard logic circuits is useful in practical exercises; the developed Fredkin element can be used in laboratory classes.

Thearticle substantiates the necessity of developing mathematical models of heat exchangers. A review of the methods of parametric and non-parametric identification of heat exchangers based on experimental data, as well as on material and heat balances is given. The author discusses advantages and disadvantages of these methods. The input, output, and intermediate parameters are selected as the main parameters of the object of study (shell-and-tube evaporator of the oil stabilization unit). The statement of the control problem is given. A mathematical model of the evaporator is developed in the form of a heat balance in a differential form. The coefficients in the heat balance equations are expressed through technological and design parameters. A transition was made from the obtained system of ordinary differential equations to expressions in the form of a system of transfer functions over various channels. The possibility of constructing a mathematical model of the studied object with the adjustment of the coefficients in the model using the experimental data of the current unit was suggested. The initial data were obtained from the trends of the process parameters. The resulting automatic control system is implemented using the tools of the software package Simulink. The search for coefficients in the model according to the selected criterion was performed using the fminsearch optimization function. As the initial search conditions, pre-calculated values of the coefficients of the model, presented in the form of heat balance, are accepted. The quality of the model was estimated by the average relative error of approximation. The proposed method for identifying the parameters of a dynamic shell-and-tube evaporator model improves the accuracy of the models. Research results were obtained using the Matlab software package. The proposed model of the object can be applied in the development of simulators, the study of the operating modes of the system, and in process control using mathematical models.

The relevance of the task considered in the paper is connected with the use of empirical models and classification methods for the preprocessing and preparation of data, and on their basis, increasing of accuracy and objectivity of decisions made as well as with the consideration of observed systems and tasks, and the use of statistical data. The paper is aimed at considering the identification method selection task to increase its efficiency performance on the base of a specific applied task under continuous data include. For the set task to be handled, the paper investigates the application of machine learning methods on the base of real time-collected statistical data about customer actions in self-service retail shops with a special device for scanning bar codes of goods. The obtained results allow classifying data into two categories (i.e. to identify target states. In the paper, this is the identification of frauds on the base of customer actions. The selected models and the ways to improve their efficiency can be used directly in the areas where staff and clients’ supervision and control in real-time (i.e. based on their e-actions) are of importance. The significance of the study is greatly connected with the outcome according to which classification methods used to consider various tasks show different efficiency levels. In the conducted study is given the method which determines how to build and select the most efficient models for solving binary classification and identification tasks. This process is limited to the series of formal operations, which can be performed by solving any classification task. Efficiency was evaluated with help of ROC curves, and the efficiency of machine learning methods’ performance was measured with help of building models’ ensembles, using cross-validation, special metrics by training models, and resembling.

The most common method of controlling asynchronous motors is vector control with the installation of sensors directly on the motor. The presence of sensors in the control system increases the risk of equipment failure. The most effective way to improve the quality characteristics of the electric drive,in particular, with vector control, is to approach sensorless methods of controlling an induction motor. Purpose: to develop a method for calculating the speed and position of the rotor of an induction motor with a sensorless vector control with fast programmed calculation time and with a simple implementation of regulation, taking advantage of complex calculations. Methods: the article considers a computer with sensorless control of an induction motor, obtained by solving the system of Park-Gorev equations in complex form. Conducting a simultaneous calculation for two projections of variables using recording in complex form allows you to speed up the calculation speed. Verification of the results was carried out using computer simulation. For these purposes, an asynchronous motor model was built in the MatLab software. Results: a computer assembled on the basis of the solution proposed in this article, with high accuracy (0,5 %) determines the value of the engine speed, has a simple and flexible structure. The solution can be scaled and applied in other versions of the electric drive due to its versatility. Practical relevance: a solution of the Park-Gorev system of equations in a complex form is proposed. A base has been obtained for creating an asynchronous motor control system with an integrated computer. The application of the method considered in the article allows the use of a microprocessor of lower performance and power, which significantly reduces the cost of the hardware of the control system.

When the distance between electric charges tends to zero, the potential energy of the electrostatic field tends to infinity, which is not good. Possible attempts to save the situation by reasoning about the impossibility of achieving a zero distance due to the finite size of charged objects are unproductive, since it is believed that, for example, electrons and positrons have no sizes. The purpose of the study is to exclude the possibility of developing infinitely large electrostatic energy. The relevance of the work is due to a significant increase in the role of electrostatic energy in connection with the start of mass production of electric vehicles and the need for the development of theoretical support in this regard. Definitions are given. Definition 1. The total stored energy is the energy of a system or an object equal to the maximum work that a system or object can do if it or he is given such an opportunity. Definition 2. The conditional realized stored energy is a part of the total stored energy of a system or object equal to the work that the system or object can do, limited by the condition that excludes the possibility of the system or object performing the maximum work that the system or object can hypothetically perform. Definition 3. Conditional unrealizable stored energy is a part of the total stored energy of a system or object equal to the work that the system or object cannot perform, limited by the condition that excludes the possibility of the system or object performing the maximum work that the system or object can hypothetically perform. A number of theorems are proved, including Theorem 1 - the stored energy is always positive; Theorem 6 - the field energy of a system of two charged spheres, one of which is completely inside the other, is a constant, i.e. independent of the location of the inner sphere.