Articles, Books, & Book Chapters

Permanent URI for this collectionhttps://dspace.kstu.uz/handle/123456789/4865

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Improving Energy Efficiency in Metalworking Machine Tools: Vector Control of Electric Drives Using a Frequency Converter and System Modeling
(2026-09-10) Sardorjon Samiev; Shokhabbos Doliev; Farrukh Juraev; Sunnatjon Farxodov; Ramziddin Toshtemirov
Today, the mechanical processing and treatment of metals are of great importance in the development of industrial sectors. Therefore, in the process of mechanical metalworking, a need arises to create new modern equipment or improve existing devices. In industrial sectors, there are several problems with devices and machine tools (such as the 1K62 lathe-screw cutting machine) used in the mechanical processing of metals, including the turning of cylindrical and conical parts, machining their external and internal surfaces, thread cutting, and surface polishing. Specifically, it is difficult to precisely control the spindle speed during the metal-cutting process; energy consumption is high due to the high starting current (5–7 times the nominal value) of asynchronous motors during machine operation; the vibration level is high during operation; and there is no torque control. These problems can be eliminated by using scalar (simple) and vector control methods of frequency converters. In this case, the vector control method was used in the research because it has several advantages as a solution to these problems. As a result, it was demonstrated during the research process that the spindle speed can be reduced to 12.5 rpm. This made it possible to precisely control the spindle speed, maintain torque at low speeds, increase energy efficiency, reduce the load on mechanical transmissions, and ensure the stability of the cutting process. In addition, by operating the asynchronous electric motor through a frequency converter, it is possible to increase the efficiency and service life of such machine tools. This is of significant importance in the process of optimizing the electrical power supply system of the machine tool
Modeling and Analysis of the Process of Fractional Separation in a Rectification Column
(Publisher Name Springer, Cham, 2026-09-02) Doliev Sh.; Farkhodov S.; Yusupov X.; Toshtemirov R.
Today, oil, gas, and chemical industries, rectification columns are considered one of the most critical pieces of industrial equipment in the process of separating liquids into fractions. Therefore, this article presents a simulation of the separation of benzene and toluene into fractions within a rectification column using Aspen Plus software, along with an analysis of this process. This modeling approach enhances the ability to study and optimize the technological process by conducting experiments based on a modern software platform, rather than performing real-world physical and practical experiments. This research was conducted to optimize the fractionation process of the liquid mixture and increase the purity of the separated components, thereby achieving a higher level of separation efficiency. The modeling process carried out in the study improved the ability to control variables such as temperature, pressure, and reflux ratio. The optimal control of these parameters made it possible to improve the quality of the distillate and bottom product emerging from the rectification column. The results determined that it is possible to separate benzene at 90% purity and toluene at 99% purity in the rectification column. By utilizing such modern modeling methods and software, it is possible to obtain suggestions and recommendations for increasing efficiency and optimizing the substance fractionation process.
Assessing the Stability of Regional Energy Supply Systems: Econometric Models and Forecasts
(American Journal of Economics and Business Management, 2026-09-21) Doliev Sh.
This study investigates the econometric modeling and forecasting of energy consumption dynamics within the energy supply system. Per capita primary energy consumption was selected as the indicator of energy consumption in the energy supply system, and the analysis was conducted using annual data covering the period from 1990 to 2025. First, the descriptive statistical characteristics of the indicator were assessed, revealing an overall declining trend in energy consumption over the study period. The dynamics of energy consumption were modeled using the ARIMA(1,1,3) model, and the forecasting accuracy of the model was evaluated using the MAPE, MAE, and RMSE metrics. The estimated ARIMA(1,1,3) specification yields R² = 0.93, while the forecast evaluation reports MAPE = 3.14%, MAE = 597.96 kWh/person, and RMSE = 749.64 kWh/person. The baseline forecast indicates a decline in per capita primary energy consumption from 15,355.95 kWh/person in 2026 to 13,760.47 kWh/person in 2030, equivalent to approximately 86.3% of the 2025 level. The results demonstrate the usefulness of a transparent time-series benchmark for short- and medium-term energy planning while also highlighting the need to interpret forecasts conditionally on historical dynamics.
Dynamic Modeling Analysis of a Doubly-Fed Induction Generator-Based Wind Energy System
(Eng. Proc. MDPI, 2026-09-11) Sardorjon Samiev; Shokhabbos Doliev; Javlonbek Khamraev; Golibjon Makhmatqulov; Khurshid Yusupov
The increasing integration of wind energy into modern power systems introduces significant challenges in maintaining frequency stability and power quality due to the stochastic nature of wind speed, particularly in microgrid environments. This study focuses on the modeling and control of a wind energy conversion system based on a Doubly Fed Induction Generator (DFIG) operating in conjunction with an external power supply system. A comprehensive simulation model of the wind energy system was developed in MATLAB (R2023b), incorporating both the wind turbine and power converter subsystems. The control strategy is based on stator flux-oriented vector control, which enables independent regulation of active and reactive power, combined with space vector pulse-width modulation (SVPWM) to improve the performance of the power electronic converters. The system employs a dual-converter structure, where the rotor-side converter ensures bidirectional power flow and the grid-side converter maintains the DC-link voltage. The simulation results demonstrate that the proposed control system ensures fast dynamic response and stable operation under variable wind conditions. In particular, the stator current reaches a steady state within 0.01 s, satisfying the specified technical requirement for transient performance. Additionally, the DC-link voltage is effectively stabilized at approximately 700 V, ensuring reliable operation of the converter system. The use of SVPWM contributes to improved switching performance and efficient synthesis of voltage vectors, enhancing overall system stability. The developed model also confirms the stable operation of the wind energy system within a microgrid, ensuring coordinated interaction between system components under fluctuating wind conditions. Compared to conventional approaches, the applied vector control strategy provides effective decoupling of power components and improved dynamic characteristics for the system. The results obtained validate the effectiveness of the proposed modeling and control approach for small-scale wind energy systems and demonstrate its applicability for improving the stability and performance of renewable energy integration in modern power systems.

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