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Quarterly published "Inventi Impact: Electrical Engineering" publishes high quality unpublished as well as high impact pre-published research and reviews related to all the areas of electrical engineering including power engineering, electrical machines, instrumentation and control, electric power generation, transmission and distribution etc.
This paper takes a typical 220 kV three-phase three-limb oil-immersed transformer as\nan example, this paper building transient field-circuit coupled model and 3D coupled magneto\n-fluid-thermal model. Considering a nonlinear Bââ?¬â??H curve, the magneto model uses the field-circuit\ncoupled finite element method (FEM) to calculate the magnetic flux distribution of the core and the\ncurrent distribution of the windings when the transformer is at a rated current and under direct\ncurrent (DC) bias. Taking the electric power losses of the core and windings as a heat source,\nthe temperature inside the transformer and the velocity of the transformer oil are analyzed by\nthe finite volume method (FVM) in a fluid-thermal field. In order to improve the accuracy of the\ncalculation results, the influence of temperature on the electrical resistivity of the windings and\nthe physical parameter of the transformer oil are taken into account in the paper. Meanwhile, the\nconvective heat transfer coefficient of the FVM model boundary is determined by its temperature.\nBy iterative computations, the model is updated according to the thermal field calculation result\nuntil the maximum difference in hot spot temperature between the two adjacent steps is less than\n0.01 K. The result calculated by the coupling method agrees well with the empirical equation result\naccording to IEC 60076-7....
This article presents a comparative study of the storage of energy produced by photovoltaic panels by means of two types of batteries: Lead–Acid and Lithium-Ion batteries. The work involved the construction of a model in MATLAB-Simulink for controlling the loading/unloading of storage batteries with energy produced by photovoltaic panels through a buck-type DC-DC convertor, controlled by means of the MPPT algorithm implemented through the method of incremental conductance based on a MATLAB function. The program for the MATLAB function was developed by the author in the C++ programming environment. The MPPT algorithm provides maximum energy transfer from the photovoltaic panels to the battery. The electric power taken over at a certain moment by Lithium-Ion batteries in photovoltaic panels is higher than the electric power taken over by Lead–Acid batteries. Two types of batteries were successively used in this model: Lead–Acid and Lithium-Ion batteries. Based on the results being obtained and presented in this work it may be affirmed that the storage battery Lithium-Ion is more performant than the Lead-Acid storage battery. At the Laboratory of Electrical Machinery and Drives of the Engineering Faculty of Bacau, an experimental stand was built for a storing system for electric energy produced by photovoltaic panels. For controlling DC-DC buck-type convertors, a program was developed in the programming environment Arduino IDE for implementing the MPPT algorithm for incremental conductance. The simulation part of this program is similar to that of the program developed in C++. Through conducting experiments, it was observed that, during battery charging, along with an increase in the charging voltage, an increase in the filling factor of the PWM signal controlling the buck DC-DC convertor also occurred. The findings of this study may be applicable to the storage of battery-generated electrical energy used for supplying electrical motors in electric cars....
Hybrid excitation synchronous motor (HESM) offers the advantages of a convenient flux regulation and a wide range of available\nspeeds. As such, it may be conveniently employed in the fields of electric vehicle and aerospace. In this paper, based on a suitable\ncontrol strategy for vector and speed partition, we put forward a speed control method for HESM which shows optimal efficiency.\nOn the one hand, our method aims at minimizing the copper loss by an optimal configuration of the q-axis current, the d-axis\ncurrent, and the excitation current under the constraint voltage at the armature end. On the other hand, we conduct a comprehensive\nanalysis of the effects of the flux-weakening speed coefficient on the operating performance of the motors and suggest a\nself-adaptive control method to regulate that coefficient and further improve the overall performance of the motors, including\ntheir speed-range regulation, their efficiency, and their dynamical properties. The proposed flux-weakening control method has\nbeen assessed by simulations and HESM-driven experiments. Results have confirmed the feasibility and optimality of our method....
Recently, the use of DC microgrid distribution system has become more attractive than\ntraditional AC systems due to their energy efficiency and ability to easily integrate with renewable\nenergy sources and batteries. This paper proposes a 500 V DC microgrid which consists of a 20 kWp\nphotovoltaic panel, batteries, and DC loads. A hierarchical control strategy to ensure balance power\nof the DC microgrid and the maintenance of common DC bus voltage is presented. The capability\nof exchanging power energy of the microgrid with the power system of neighborhood buildings\nis also considered. Typical operation modes are simulated in the Matlab/simulink environment to\nconfirm the good performance of the controllers and the efficiency of appropriately controlling the\nchargeââ?¬â??discharge of the battery system. This research is expected to bring benefits to the design\nand operation of the system, such as reducing the capacity of batteries, increasing the self-supply of\nbuildings, and decreasing the electricity demand from the AC grid....
The AC drive is an important component and the most common element of any manufacturing process. A particularly serious task is the proper assessment of the AC drive’s technical condition, as its failure can cause problems for entire units and complexes of industrial enterprises. At present, there are several approaches either to determine electric drives’ condition or to find certain defects. Frequently, these methods require the installation of additional equipment that exceeds the price of the electric drive by several times. In this work, a simple approach is proposed. It includes the use of a diagnostic curve to assess the condition. This diagnostic curve is produced from the measurement results of the current sensors on the drive. Based on the Park vector modification, this is a simple and affordable way to obtain real-time information. The obtained curve can be used for the following purposes: directly for condition assessment by visual monitoring, as a sign for diagnostic systems built on artificial intelligence methods, for dynamic tuning of the drive control system. The article gives the algorithm for obtaining the diagnostic curve, showing its efficiency for model and field experiments. In model experiments, the faults in the rotor and stator of the drive were simulated; in field experiments, the state was analyzed by changing the load on the motor....
A high-input voltage 2-phase series-capacitor (2-pscB) DC-DC buck converter is theoretically analyzed, designed, and implemented.\nA new design approach for an automatic current sharing scheme was presented for a 2-phase series-capacitor synchronous\nbuck converter. The series-capacitor voltage is used to achieve current sharing between phases without a current sensing\ncircuit or external control loop as each phase inductor charges and discharges the series capacitor to maintain its average capacitor\nvoltage constant. A novel isolated gate driver circuit to accommodate an energy storage capacitor is proposed to deliver isolated\ngate voltages to the switching transistors. An I2 control scheme that uses only one feedback path control for the four gate drivers is\nproposed to enable higher voltage conversion. An experimental 110-12V 6A load prototype converter was designed, and its\ncurrent sharing characteristics were experimentally verified....
This paper proposes a high-performance indirect control scheme for torque rippleminimization in the switched reluctancemotor (SRM) drive system. Firstly, based on the nonlinear torque-angle characteristic of SRM, a novel torque sharing function is developed to obtain the optimal current profiles such that the torque ripple is minimized with reduced copper losses. Secondly, in order to track current accurately and indirectly achieve high-performance torque control, a robust current controller is derived through the Lyapunov stability theory. The proposed robust current controller not only considers the motor parameter modeling errors but also realizes the fixed frequency current control by introducing the pulse width modulation method. Further, a disturbance-observer-based speed controller is derived to regulate the motor speed accurately, and the load torque is considered an unknown disturbance................................
The force ripple of a permanent magnet synchronous linear motor (PMSLM) caused by multi-source disturbances in practical applications seriously restricts its high-precision motion control performance. The traditional single-mechanism model has difficulty fully characterizing the nonlinear disturbance factors, while the data-driven method has realtime limitations. Therefore, this paper proposes a hybrid modeling framework that integrates the physical mechanism and measured data and realizes the dynamic compensation of the force ripple by constructing a collaborative suppression algorithm. At the mechanistic level, based on electromagnetic field theory and the virtual displacement principle, an analytical model of the core disturbance terms such as the cogging effect and the end effect is established. At the data level, the acceleration sensor is used to collect the dynamic response signal in real time, and the data-driven ripple residual model is constructed by combining frequency domain analysis and parameter fiing. In order to verify the effectiveness of the algorithm, a hardware and software experimental platform including a multi-core processor, high-precision current loop controller, real-time data acquisition module, and motion control unit is built to realize the online calculation and closedloop injection of the hybrid compensation current. Experiments show that the hybrid framework effectively compensates the unmodeled disturbance through the data model while maintaining the physical interpretability of the mechanistic model, which provides a new idea for motor performance optimization under complex working conditions....
In this paper, an U-shape flux barrier rotor concept for a hybrid excited synchronous\nmachine with flux magnetic bridges fixed on the rotor is presented. Using 3D finite element\nanalysis, the influence of axial flux bridges on the field-weakening and -strengthening characteristics,\nelectromagnetic torque, no-load magnetic flux linkage, rotor iron losses and back electromotive force\nis shown. Three different rotor designs are analyzed. Furthermore, the field control characteristics\ndepending on additional DC control coil currents are shown....
Compared to the conventional finite control set model predictive control (FCS-MPC), the double vector model predictive current control (DVMPCC) for permanent magnet synchronous motors (PMSMs) has a better steady-state performance without significantly increasing the switching frequency. However, determining optimal vectors with their dwell times requires a high computational burden. A low-complexity DVMPCC in the steady state was proposed in this study to address this problem. Firstly, the operating state of the motor was judged according to the speed error. During steady-state operation, the first optimal active vector was selected from three candidate vectors adjacent or identical to the active vector applied in the previous control period, reducing the number of comparisons by half. Next, the second optimal vector was selected from the other two active vectors, and the zero vector, the second optimal vector with the duty cycle, was determined according to the deadbeat condition of the q-axis current and cost function minimization. Finally, simulation and experimental results proved that the proposed low-complexity DVMPCC for surface-mounted permanent magnet synchronous motors is practical and feasible....
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