Current Issue : January - March Volume : 2019 Issue Number : 1 Articles : 5 Articles
The energy crisis and environmental concerns worldwide have helped usher in the age of\nelectric vehicles (EVs) and hybrid EVs (HEVs). The interior permanent magnet motors (IPMMs) are\nwidely used in these vehicles. The analysis of the armature reaction field is the most critical issue in\nthe study of IPMMs since it determines the characters of torque, efficiency, vibration, and the radiated\nacoustic noise. This paper provides a calculation method of the armature reaction magnetic field\n(ARMF) of an IPMM. First, the formulas of ARMF without magnetic barrier are derived. Second,\nthe relative permeance function of an IPMM is calculated. Third, the analytical solution of the\nARMF of an IPMM is derived by applying the armature reaction magnetic field with unsaturated\nrotor multiplied by relative permeance function. Finally, several results of comparisons between the\ncalculation method proposed in this paper and the finite element method are presented. Based on\nthe calculation method proposed in this paper, the magnetic barrierâ??s influence on the ARMF\nis studied. The spatial harmonic orders and time harmonic orders of the ARMF of IPMM are\nrevealed respectively....
The knowledge about the behavior of cables is substantial in cases of transients or in\ncases of faults. However, there are only a few models that are tailored to the current requirements\nfor calculations of transient phenomena in three-phase cable systems. These models are based on\ncomplex structures. PI-section cable models with simple structures were previously qualified only\nfor calculations in the frequency domain. A new full frequency-dependent cable model to simulate\ntransient phenomena is introduced and validated. The model is based on lumped parameters with\ncascaded frequency-dependent PI-sections. For the implementation and the integration in simulation\ntools, it is important to investigate the impact of the PI-section parameters to the accuracy, the stability\nand the mathematical robustness. In this work, the impact of the frequency dependence of cable\nparameters, the length distribution and the number of PI-sections on the results of the developed\nthree-phase cable model have been discussed. For simulations in the time domain, two algorithms\nhave been presented to optimize the number of PI-sections based on a specified accuracy....
The flexible alternating current transmission systems (FACTS) have been widely used in\nmodern power systems. Because of the presence of the FACTS devices, distance relays in transmission\nlines may inaccurately locate fault locations. Therefore, it is significant to find a mechanism for\nlocating fault in transmission lines connected to FACTS in which a static var compensator (SVC) is\ninvestigated in this work. Based on the development of a phasor measurement unit (PMU) with global\npositioning system (GPS), this paper proposes a new method for calculating apparent impedance seen\nby the distance relay location while a short-circuit fault occurs in a transmission line connected the\nSVC to the midpoint of the line. According to the method, sampled voltage and current measurement\nat the relay and SVC locations are synchronized using PMUs and the synchronized measurements\nare then used to calculate a new apparent impedance and to locate the fault location in the line.\nThe method in this paper has the capability for fast calculation and it also has the robustness for\nidentifying different fault types in power systems. Matlab/Simulink software is applied to simulate\nthe study results and to evaluate the correctness of the modeling and effectiveness of the proposed\nmethod for locating fault in this paper....
The current tracking control strategy determines the compensation performance of shunt active power filter (SAPF). Due to\ninadequate compensation of the main harmonic by traditional proportional integral (PI) control, a control algorithm based on PI\nand multi vector resonant (VR) controllers is proposed to control SAPF. The mathematical model of SAPF is built, and basic\nprinciple of VR controller is introduced. Under the synchronous reference frame, the proposed control method based on pole zero\ncancellation is designed, which narrows the order of the control system and improves the system dynamic response and the\ncontrol accuracy. Then the feasibility of the method is demonstrated by analyzing the closed loop frequency characteristics of the\nsystem. Finally, the simulation and experimental results are carried out to verify the performance of the proposed method....
Corrosive sulfides in transformer oil could react with copper wire to produce cuprous\nsulfide, causing insulation failure. At present, both the quantitative measurement method and\ndistribution of sulfur components in operating oil are not clear yet. In this paper, the existing\ntypes and contents of sulfides in oil samples with different alkyl groups and different voltage\nlevels were investigated. With quantitative testing methods, the distribution of sulfur composition\nin the operating oil was analyzed. Results showed that the thiophene sulfide in transformer oil\nexisted mainly in the form of benzothiophene with an unsaturation of 6 and dibenzothiophene\nwith an unsaturation of 9. The content of monosulfide sulfide with unsaturation of 3 or 6 was the\nhighest. The disulfide existed basically in the form of Dibenzyl disulfide (DBDS). The influence of\nsulfides on the oil quality were analyzed on this basis. Results showed that the existence of sulfides\nwould increase the moisture content in oil. The absorbed moisture could cause the decrease of the\nbreakdown voltage and rise of the dielectric loss. The above study could provide some engineering\npractice for understanding the sulphide distribution in transformer oils and further prevent the sulfur\ncorrosion faults....
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