Electrical Engineering and Power Engineering

Adaptive models of the four-switch buck-boost converter

O.V. Vasylenko, G.V. Snizhnoi — Sat, 14 Jun 2025 00:00:00 +0300

Purpose. Development of an economic adaptive model for the power stage of a four-switches buck-boost converter (FSBB) together with a control system that adequately simulates all modes of its operation.

Methodology. The main research method is mathematical modeling; empirical formulas are used to calculate the model parameters; a behavioral programming approach is used for the structural synthesis of the converter model.

Findings. The prospects for using a FSBB converter in energy conversion systems where the input and output voltages vary relative to each other are shown. The advantages of using computer-aided design (ECAD) programs for modeling converters together with control systems as multi-domain systems are identified. Approaches to modeling converters together with control systems are analyzed and limitations of using models based on "state space averaging" for studying electromagnetic characteristics and temperature management in the power stage of the converter are indicated.

A method for forming a dynamic FSBB model for ECAD program Micro-Cap 12 based on simulating the behavior of power switches over time and replacing them with programmable resistors is proposed. To control the rigidity of the model and accelerate the simulation, optimal values of the resistances of these resistors are obtained. A converter model was developed for the PSIM program too and a comparative analysis of modeling and simulation quality indicators in the Micro-Cap and PSIM programs was conducted. Recommendations for the fields of use of the developed models have been formed.

Originality. The scientific novelty of the work lies in the way of presenting an economical Spice-compatible dynamic model of FSBB, in which the power stage and the control system are integrated through the use of behavioral models for power switches. In these behavioral elements, the switching conditions are programmed by comparing the carrier signal with the reference of the PWM control subsystem; both signals are normalized and the reference is proportional to the duty cycle. By dynamically redefining the duty cycle parameter, the model is adapted for any converter mode (buck, boost, and transition), which makes it universal. A simple converter model was also developed together with a control system for the PSIM program, which makes it possible not only to analyze electromagnetic characteristics, but also to import to SmartControl the necessary transfer functions for optimal controller synthesis.

Practical value. The proposed models allow analyzing dynamic processes in the FSBB converter, optimally combining such contradictory indicators of simulation quality as accuracy and efficiency. The model for Micro-Cap allows to adequately simulate the transient processes of the power stage of the converter, since it is obtained without prior linearization and averaging, in addition, it can be supplemented with temperature coefficients, this option is absent for the PSIM model. The PSIM model makes it possible to obtain a transfer function for the synthesis of the control system.

Optimization of arc current pi regulator parameters by sofrware modeling

Sat, 14 Jun 2025 00:00:00 +0300

Purpose. To create a computer model of a converter operating on a plasma arc and to determine the optimal values of the coefficients of the PI current controller, ensuring optimal switching between its operating modes and high quality of control processes. In doing so, use the MATLAB / Simulink software.

Methodology. Computer simulation method, separation method – optimal filtering and optimal deterministic control and methods for adjusting regulators.

Findings. A multilevel model was formed, the values of the PI current regulator tuning parameters were determined, at which the DC-DC converter observes optimal switching between its operating modes and high quality of control processes. Analytical methods for determining the PI regulator parameters do not allow obtaining optimal settings, since they are based on highly simplified models, but their use is necessary to obtain preliminary settings, without which accurate tuning can take a long time. It was established that the optimal regulator provides optimal resistance to disturbances at the input and output of the object and compensates for changes in parameters in a similar way. The system has a satisfactory transient process under non-zero initial conditions in response to a given reference influence and to a change in the set point, has good stability characteristics and is not very sensitive to disturbances and changes in the parameters of the object.

Originality. An approach to determining a continuous linear model of a power converter of electrical energy is proposed and the optimal choice of parameters for setting the regulator of its control system is given, which form the basis for constructing any plasma torch power supply system, which ensures the specified accuracy of regulation and speed of operation.

Practical value. The proposed principle of solving the problem of determining the coefficients of PI regulators can be applied to various dynamic objects, the description of which is permissible using linear and differential equations. The results presented in the work can be used for the design of pulsed power supplies for electrical technologies.

Research of energy expenditures for mechanical mixing of raw materials in a biogas reactor

M.O. Spodoba, O.O. Spodoba — Sat, 14 Jun 2025 00:00:00 +0300

Purpose. Study of energy consumption by mechanical mixers and selection of an energy-efficient mixing device to ensure reduction of energy consumption for the biogas production process and increase interest in its further processing into other types of energy.

Methodology. Comparative analysis and use of mathematical modeling methods to determine the amount of energy consumed for mixing, generalization of the results obtained.

Findings. The formation of the energy system consists in including renewable alternative energy systems, including biogas technologies. The energy efficiency of which depends on the amount of energy consumed for the processes of intensification of the fermentation of raw materials. One of the main means of intensification is careful and frequent mixing of raw materials during fermentation. The presence of various types of devices for mixing substances in reactors confirms the relevance of the issue of developing energy-efficient means to accelerate fermentation and increase the profitability of further actions with biogas and its processing. The most rational ways to increase the energy efficiency of mixing are to establish the dependences of energy consumption by mechanical mixing devices, to choose a rational type of mixer, which includes the search for rational mass-dimensional characteristics that ensure uniform flows of raw materials in the biogas reactor and at the same time spend the least amount of energy for mixing. Performing the above actions ensures the determination of rational mass-dimensional characteristics of the mixer, which significantly reduces energy consumption for mixing and increases the profitability of implementing biogas technologies into the energy system.

Originality. The types of electric machines used as electric drives of mixing devices are analyzed. Taking into account the control systems of electric drives and the cycle diagrams of their operation, as well as the features of mixing the substance, the change in the Euler hydrodynamic similarity criterion for different types of mechanical mixers with the same geometric parameters of biogas reactors, the levels of organic raw materials and the same speed mode of movement of the working body of the mixer, the power consumption for the technological process – mixing is established. A comparative analysis of the influence of the type and geometric dimensions of mechanical mixers on the energy consumption for mixing the volume of the substance in a closed tank when using a single-phase asynchronous motor as a mixer drive is carried out. Using a polynomial dependence, an equation was obtained that describes the change in the power of the electric drive from the change in the frequency of rotation of the working body of a two-tier mixer in which the blades are installed at an angle of 900.

Practical value. The results presented in the work can be used to increase the energy efficiency of biogas plants. The direction of further research on the consumption of reactive power by electric motors during the technological cycle of the mixer operation has been established, which will allow determining the pattern of changes in reactive power consumption and outlining the directions of movement towards its reduction.

Research of thermal processes of an IGBT module-based inverter

S.P. Lushchin, D.P. Paxar — Sat, 14 Jun 2025 00:00:00 +0300

Purpose. Study of thermal processes of an inverter based on an IGBT module for used in a frequency converter to control the operation of an asynchronous motor.

Methodology. Analytical and computational methods to analyse thermal processes of an inverter based on an IGBT module.

Findings. The study of thermal processes of the SKM200GB12T4 inverter based on the IGBT module was performed using the SemiSel program. A mathematical model of the cooling process of the SKM200GB12T4 inverter was developed. The dependence of the dynamic thermal impedance Zth(s-a) on time, which is described by an exponential function, was obtained. The value of the time constant for this dependence, which characterizes the rate of change in the cooler temperature, i.e. the quality of its operation, has been calculated. The thermal time constant τ = 1.44 s indicates the time required to reach a temperature difference of approximately 63% of its stationary value. This low value reflects the effective cooling due to the high air flow velocity (7 m/s) and air flow rate (426.43 m³/h), which is critically important for maintaining the IGBT junction temperature below 175 °C during overload.

The values of the inverter temperature maxima during overload were obtained. For an overload of 10.94 seconds, the maximum temperature for IGBT transistors is 120.85 °C, and for diodes – 123.4 °C. The case temperature Tc = 71.21 °C and the radiator temperature Ts = 63.56 °C remain the same for transistors and diodes and do not exceed the maximum operating temperature of the module due to the stability of the cooling system. However, overheating can increase with prolonged loading, resulting in the degradation of semiconductor devices.

The temperature and power variation processes at nominal load and in overload mode for one period have been studied using the SemiSel program. The temperature change graphs reflect the stability of the temperature at various points, such as the transitions of IGBT transistors and reverse diodes, due to effective thermal control. The power graph indicates cyclical changes in losses, with peaks in the phases where current and voltage are maximum. These data confirm the suitability of the module for use in control circuits.

Originality. Based on the graphical analysis of the kinetic dependencies of temperature and inverter power, a mathematical model of the cooling process of the SKM200GB12T4 inverter was developed, that describes the dependence of the dynamic thermal impedance Zth(s-a) on time. The thermal time constant for this dependence, which characterises the rate of change of the cooler temperature, was calculated.

Practical value. The results of the study of the thermal characteristics of the SKM200GB12T4 inverter can be used to optimize the operating modes of the frequency converter for controlling the operation of an asynchronous motor.

Improving the protective properties of electrical equipment in low-voltage cabinets of complete transformer substations auxiliaries NPP

O.G. Sereda, L.B. Zhorniak, O.G. Sereda — Sat, 14 Jun 2025 00:00:00 +0300

Purpose. Analyze the existing problems in the relay-current protection system of electrical installations of 0.4 kV auxiliary substations of nuclear power plants, which do not allow the implementing the "long-range backup" mode, as well as to increase the sensitivity of relay protection devices to remote short-circuit currents by using additional criteria for identifying emergency modes in order to ensure selectivity and and protection against remote redundancy failures.

Methodology. Method of system analysis and synthesis, as well as the theory of electromagnetic transient processes in electric power systems for diagnostics of emergency modes of operation of distribution electrical circuits.

Findings. The article shows the need and provides scientific and technical justification for proposals to modernize relay-current protection systems for 0.4 kV electrical installations using digital technologies to implement the requirements of "long-range backup". A scientifically sound technical solution is provided for upgrading circuit breakers using microprocessor protection devices, the output circuits of which affect independent electromagnetic tripping devices of these circuit breakers. This solution allows for an in-depth analysis of processes in electrical circuits and the implementation of "long-range backup" by building high-speed selective protection and increasing the sensitivity of the protection to short-circuit currents. As a result of modernization of electrical installations of 0.4 kV NPP auxiliary substations due to implementation of new types of relay-current protection, the following is possible: significant reduction of protection response time at all stages between the source and receiver of electric power, both in the normal mode and in the "long-range backup" mode, and, accordingly, significant reduction of thermal effects on elements of electrical installations both from the flowing short-circuit current and from the effect of an electric arc; significant increase in sensitivity of protection to remote short-circuit currents, which will eliminate both cases of possible protection failure and its false operation. After modernization of the entire protection system due to the use of microprocessor protection devices, the existing structure of the protection system will be completely preserved without replacing switches of all stages, which will allow significant savings in time and financial costs compared to other modernization options.

Originality The article presents a technical solution for upgrading circuit breakers with microprocessor protection devices, in which the output circuits act on independent electromagnetic releasing mechanisms of these devices.

Practical value. The development allows increasing the reliability of emergency protection automation, as well as fire safety of auxiliary substations of nuclear power plants with a voltage of 0.4 kV.