A method is presented for selecting optimal ratios of the geometric dimensions of a power electromagnet with a transverse magnetic flux corresponding to the minimum weight. The criterion of optimal choice is the indicator of specific working capacity—the ratio of the maximum mechanical work of an electromagnet to the total mass of its active volume. The main results were obtained using finite element modeling of the magnetic field. Based on the performed analysis, recommendations on the use of optimal size ratios in design tasks are prsented.
A rapid technique for determining the technical condition of batteries based on electrochemical impedance spectroscopy (EIS) and Nyquist curve analysis is considered. Unlike traditional Coulomb methods, which require a full charge and discharge cycle, the proposed approach allows for the rapid assessment of state of charge (SOC), state of health (SOH), functional state (SOF) and internal degradation processes without taking the battery out of service for a long time. The method is based on the application of low-signal harmonic effects in a wide frequency range and the subsequent construction of a complex frequency response of the impedance. It is shown that the parameters of the Nyquist curve—the active component of the resistance, the radius and shape of the semicircle, as well as the low-frequency diffusion region—correlate with electrochemical and diffusion processes in the battery and change with aging. An algorithm for interpreting spectra for diagnosing degradation and comparative analysis of batteries of various types is proposed. The possibility of a significant reduction in diagnostic time and energy consumption while maintaining high information content of measurements is substantiated. It is shown that the use of the EIS method as part of battery monitoring systems for transport and stationary electrical complexes makes it possible to increase the accuracy of assessing their life and reliability.
Presented are the results of a study of degradation processes in traction batteries. The main mechanisms and causes affecting the reduction of the effective capacity of lithium‑ion batteries were investigated. Using a simulation model of an electric vehicle, the battery degradation process was analyzed and optimal operating modes were determined. It was found that the amplitude of the traction current significantly affects the degree of battery degradation. The study established that the key factor influencing the rate of loss of battery charge capacity is the intensity of current draw. To mitigate the effects of high discharge currents, the use of next‑generation batteries with improved power characteristics and an increased number of possible charge/discharge cycles is proposed. In the MATLAB/Simulink environment a model of the Moskvich‑3 electric vehicle, classified as third class by power classification, was developed, equipped with both a standard and a hybrid 25 kWh battery.
A method for developing a simple analytical model is considered, which clearly shows the influence of input parameters on the voltage of battery cells in charge/discharge mode. The model is an algebraic expression without nonlinear coefficients and differential components, uniform for all modes, and independent of secondary characteristics. This allows the model to be considered as an independent and simple tool for solving various optimization problems and to build compact simulation models based on it, the structure of which remains simple and unchanged for all modes. The advantage of these models is significantly manifested in solving practical problems in which it is necessary to analyze the simultaneous interaction of a large number of cells in state-of-the-art energy-intensive batteries, where the speed of response and saving computing resources are crucial factors.
A simulation model is presented for investigating the dynamics of the system “Productive formation—electric submersible centrifugal pump (ECP)—pump‑compressor tubing—wellhead” in transient modes under variable‑frequency control. The model is intended for analysis of unsteady (transient) processes arising from changes in the rotational frequency of the ECP’s submersible electric motor. The model comprises three interrelated subsystems: reservoir hydrodynamics, a dynamic‑similarity model of the electric centrifugal pump, and flow dynamics in the pump‑compressor tubing. The influence of the pump unit’s ramp‑up (start‑up) time on the system’s dynamic parameters was investigated. It was found that at short ramp‑up times the system dynamics are weakly damped and accompanied by significant oscillations. Increasing the ramp‑up time reduces the oscillation amplitudes and yields a smoother transition of the system to steady‑state operation.
The development and approbation of a simulation model of the power circuit of a mining excavator with a valve-inductor electric drive are presented. The model is designed to analyze the electrical modes of the input rectifier and the associated thermal loads of MDx-1000-28-D diode modules. Based on the data of the instrumental examination of the facility in the MATLAB Simulink environment, a model was constructed that includes subsystems of a power transformer, a rectifier, a dc link, a heat exchanger, inverters, an equivalent load, and a thermal model of a diode module. The electrical part of the model was approbated using voltage and current waveforms recorded on a real object. It is shown that the model makes it possible to determine the current and thermal modes of diode modules, including estimating the instantaneous temperature values of the crystal and the cooler surface under operational and perturbed conditions.
The synthesis of a sensorless vector‑control system for a submersible permanent‑magnet synchronous motor used in the drive of a plunger pump for a low‑yield well is considered. A distinctive feature of the plant is a long supply circuit, a transformer and a 2000 m cable line, whose total resistance exceeds the stator resistance by a factor of 5–6. It is shown that neglecting the circuit parameters in the back‑EMF observer leads to loss of system stability. An analytical limit on the proportional gain of the current controller is derived from the gain‑margin condition at the resonance frequency of the equivalent circuit for a damping ratio ζ ≈ 0.052. To estimate rotor angle and speed, a back‑EMF observer with a phase auto‑tuning algorithm for the double‑angle frequency is used; this algorithm is invariant to the sign of the speed in the pump’s reversing mode. Simulation in SimInTech confirmed an angle estimation accuracy of ±0.005 rad, stable operation during reversal, and verified the analytical stability condition.
The application of a neural network algorithm in a control system for discrete symmetry-compensating devices designed to reduce the asymmetry of three-phase distribution network modes and reactive power compensation is considered. It is proposed to use a neural network algorithm in a discrete controller of the control system to select the optimal control parameters of the control system, ensuring the maximum efficiency of the distribution network. This approach allows us to take into account the nonlinear nature of the relationships between the parameters of the network mode and the discrete states of the power part of the device. Structures of neural network models of a discrete controller are presented, and the composition of input data (features), output control parameters, and the training procedure for models for two topologies of the control system are described. A procedure for creating a training sample based on a reference calculation is considered, in which the optimal discrete state of the device is determined for each network mode. It is shown that the use of a clarifying enumeration of the most probable states formed by the neural network model allows high accuracy in selecting the control action while maintaining acceptable computational complexity. Simulation results in MATLAB Simulink confirm the operability of the proposed approach, the effectiveness of the neural network controller in selecting discrete settings, and its prospects for building intelligent control systems for discrete power electronics devices.
The features of energy processes in a mobile mining microgrid with a diesel generator set are reviewed when asynchronous motors of comparable power to an energy source are turned on. A study of frequency start of an asynchronous motor when controlling the speed of rotation of a diesel engine has been performed. Equations are derived for the starting torque of an asynchronous motor when connected to a source of commensurate power with an adjustable frequency. Results are presented of modeling and experimental studies of processes in a mobile microgrid.
When the current of lightning spreads through a grounding system, it produces a strong electric field that causes soil ionization, which in turn causes a decrease in the grounding system impulsive impedance. The CIGRE formula provides a simple analytical dependence of the grounding system impedance on current, but it is applicable only in the case of the single-layered soil. A modified version of the CIGRE formula for the two-layered soil has been developed and investigated. The characteristics of ionization processes in the two-layered soil have been studied. The most significant decrease in the grounding system impedance is observed in the case of soil with a high specific resistance of the upper layer, in which the ionization processes are more intense in nature, whereas the expansion of the ionization zone brings the grounding system closer to the well-conducting lower layer. The critical ionization field strength in the single layer model depends to a significant extent on current, whereas in the two-layer model it is almost constant, which has been established both in the processing of experimental data and in theoretical studies. An the equivalent single-layered soil is characterized not only by an equivalent specific resistance, but also by an equivalent critical field strength, which can be significantly higher (if the conductivity of the upper layer is higher than that of the lower layer) or can be lower than the standard values at high currents. For 110 and 220 kV double-circuit overhead power lines, a significant decrease (several dozens of percent) in the expected probability of reverse insulation flashover has been obtained for the case of taking soil ionization into account.
One of the effective methods for combating load asymmetry is shunt regulation of power network operating modes, which allows for the control of currents and powers (active and reactive) in different phases. The choice of a specific shunt regulation method depends on the type and distribution of load across network phases, as well as power quality requirements. This paper considers the problem of balancing the operating modes of four-wire, three-phase networks with asymmetric loads using a power controller built around a single-phase transformer and a reactive element. The power controller regulates the exchange of active and reactive power between network phases by discretely controlling the transformer transformation ratio and the resistance of the reactive element. Analytical expressions describing the electromagnetic processes in the phases of the power controller and the network are presented. Methods for calculating the parameters of controller circuit elements for balancing active powers in network phases with different ratios of active powers in the load phases are developed. The results of calculating the power controller parameters and simulating network operating modes with different load profiles are presented.
The characteristics of an induction motor with a frequency-controlled drive in the conditions of its industrial operation in the manufacture of medicines are obtained, and the features of these characteristics are revealed when starting with various loads, including time-varying loads, as well as with different acceleration times, up to the nominal frequency. By modeling the electromagnetic field using the finite element method, the currents in the stator winding and the short-circuited rotor winding were determined and the electromagnetic force and the characteristics of rotation of the rotor with automatic restructuring of the finite element grid were determined. The results of comparing computational and field experiments in steady-state and start-up modes with a time-varying load are presented. The operating characteristics of an induction motor for various acceleration durations and loads are obtained.
The magnetic field in the air gap of a slotless two‑rotor disc electric motor with permanent magnets is analyzed. An analytical model in cylindrical coordinates is developed for axial magnetization with a sinusoidal distribution in the azimuthal direction. Using Laplace’s equation and appropriate boundary conditions, expressions are derived for the magnetic potential, the magnetic field intensity and flux density in the gap, as well as for the working harmonic averaged across the gap thickness. Dimensionless parameters relating the air gap and magnet thickness to the local pole pitch are introduced, and their influence on the field magnitude is demonstrated. Radial nonuniformity of the working harmonic is noted, which is important for the design of disc‑type machines and for the verification of numerical models.
The article is dedicated to the development and experimental study of a perspective highly efficient current converter designed for use in systems for powering spacecraft in a near-Earth orbit. The design consists of a four-switch uninsulated buck–boost converter that carries out critically important functions of controlling the charge and discharge of lithium-ion batteries and stabilizing bus voltage. The key characteristics of the development are the use of modern powerful wide-bandgap GaN transistors, which allow switching losses to be minimized and the total effectiveness of the system to be increased; operation under elevated bus voltage, which makes it possible to reduce the weight and size characteristics; and the use of a new control scheme. To guarantee smoothness of operation and maximum speed of operation of the system, a mixed mode of control is realized that allows sharp changes of current and electromagnetic interference upon switching between modes of voltage reduction and increase to be avoided, which is especially important in conditions of stringent requirements for electromagnetic compatibility in space technology. The average-current method of control provides high precision of the control parameters and significantly increases the resistance to interference of the system, as well as allowing high-accuracy sensors with a high level of inertia to be used in the power section of the converter, which increases the reliability of the construction. On the basis of the results of comprehensive testing, the experimental prototype of the converter showed an efficiency comparable with the calculated values of efficiency on the level of 96
Circuit design solutions and algorithms are proposed for the operation of a small-sized semiconductor high-voltage switching device (HVSD) for regulating voltage under load, designed for oil-sealed transformers of class 6–10/0.4 kV. The device is designed to be placed as part of typical transformer substations and makes phase-by-phase change of voltage levels on the consumer side possible. The circuit of each phase of the device is based on bidirectional thyristor switches and controlled relays and provides five discrete control steps in the range of ±5
The methodology for formation of operational control points to regulate the electric mode of an electric arc furnace (EAF) while implementing a specific economic optimization strategy such as minimizing the energy consumption or maximizing the furnace productivity has been considered. The problem is solved by analyzing the electrical and operating characteristics of the EAF at each voltage tap of the furnace transformer; the electrical parameters of the electric furnace circuit and the power supply parameters should also be taken into account. The methodology is demonstrated using a domestic ultra-high-power EAF with a 100‑ton capacity, which implements a strategy for maximizing the furnace productivity and clearly illustrates the capabilities and limitations that arise in practice.
It is shown that the calculation of the control program for electrical resistance furnaces, which is optimal according to the criterion of energy consumption, can be performed by neans of linear programming, whereas the implementation of the resulting program can be carried out using a control method with a predictive model making it possible to compensate for errors in the program control based on feedback appication. A mathematical formulation of the problem in synthesizing energy-saving laws for to control electrical resistance furnaces is formulated and a method for solving thereof is proposed, which provides, as to compare to the known methods, a significant decrease in the energy consumption in the course of furnace control, a high accuracy of temperature control, as well as the possibility of taking into account constraints on the values of adjusted parameters and controlling action. An example of the implementation of the proposed method is considered.
A simulation dynamic model of linear discrete electric power is proposed. Considered are the structure and elemental composition of an electric drive an executive device of which is a six-phase electromagnetic drive designed in the form of separate mechanically connected modules. Based on the identity of the phases of an electric drive, the general principle of forming its mathematical model in the form of a system of differential equations of electrical and mechanical equilibrium of an electromechanical system is considered, supplemented by 2D arrays of values of flow coupling and electromagnetic force. A variant of their implementation in the MATLAB Simulink environment is proposed. The model takes into account the mutual influence of electromagnetic and mechanical processes, the magnetic properties of steel, and scattering fluxes and energy losses in electrical and mechanical systems. An example of using a simulation model to calculate dynamic characteristics is considered.
The problem of electromagnetic compatibility (EMC) of automated farm equipment is considered. The objects of analysis are variable frequency drives, power cabinet equipment, sensors, controllers and industrial data transmission networks. It is shown that an increase in the number of power converters increases the probability of conducted and emitted interference affecting the measurement channels. A method for calculating and engineering evaluation of interference links is proposed, including a map of sources and receivers, measurement of the level of interference, calculation of filter attenuation and assessment of sensor error before and after measures aimed at improving EMC.
This article examines the features of key basic topologies, such as a neutral-point-clamped inverter, a flying capacitor inverter, and a cascaded H-bridge inverter with an isolated DC source. It is noted that each of the topologies discussed has important advantages and occupies a specific niche in industrial applications. A relatively new topology, a three-level T-type inverter, is also discussed. The energy-efficient operation of a T-bridge with a parallel resonant circuit is examined in detail. The use of a T-bridge with an integrated resonant circuit as a universal modular cell for constructing energy-efficient basic topologies for multilevel voltage-source inverters is discussed.
