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Quarterly published "Inventi Impact: Electrical Engineering" publishes high quality unpublished as well as high impact pre-published research and reviews related to all the areas of electrical engineering including power engineering, electrical machines,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....
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................................
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....
Prediction of available energy storage power is essential for increasing the energy management performance of fuel cell hybrid electric systems (FCHES). A simple yet effective power prediction index is proposed to estimate the supercapacitor state of power. It prevents the supercapacitor’s total depletion in the battery/supercapacitor combination. Modern energy management is equipped with an equivalent consumption minimization strategy. The power prediction index is simple compared with other predictive algorithms while providing excellent efficiency compared with supercapacitor-based management strategies. A supercapacitor-based strategy is presented which extends battery life, at the cost of increased fuel consumption. However, it cannot predict the future low state of charge for the supercapacitor. In such conditions, the battery provides the demand power while fuel cells generate more current. On the other hand, the modern power prediction index energy management strategy significantly increases battery life without adding extra hardware. Moreover, fuel consumption decreased by 15.1 percent. The results show that the modern energy management strategy provides outstanding performance for battery life and fuel consumption compared with other energy management strategies due to its power limitation prediction....
Induction motors are widely applied in motor drive systems. Effective temperature monitoring is one of the keys to ensuring the reliability and optimal performance of the motors. Therefore, this paper introduces a multiplexed optical temperature sensing system for induction motors based on few-mode fiber (FMF) spatial mode diversity. By using the spatial mode dimension of FMF, fiber Bragg grating (FBG) carried by different spatial modes of optical paths is embedded in different positions of the motor to realize multipoint synchronous multiplexing temperature monitoring. The paper establishes and demonstrates a photonic lantern-based mode division sensing system for motor temperature monitoring. As a proof of concept, the system demonstrates experiments in multiplexed temperature sensing for motor stators using the fundamental mode LP01 and high-order spatial modes LP11, LP21, and LP02. The FBG sensitivity carried by the above mode is 0.0107 nm/◦C, 0.0106 nm/◦C, 0.0097 nm/◦C, and 0.0116 nm/◦C, respectively. The dynamic temperature changes in the stator at different positions of the motor under speeds of 1k rpm, 1.5k rpm, 2k rpm with no load, 3 kg load, and 5 kg load, as well as at three specific speed–load combinations of 1.5k rpm_3 kg, 1k rpm_0kg, 2k rpm_5 kg and so on are measured, and the measured results of different spatial modes are compared and analyzed. The findings indicate that different spatial modes can accurately reflect temperature variations at various positions in motor stator winding....
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