• Title/Summary/Keyword: harmonic-analysis

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A Study on the Over Current Relay Misoperation in Power System with Distributed Generations (분산전원 연계 계통에서의 과전류계전기 오동작에 관한 연구)

  • Park, Jong-Il;Lee, Kyebyung;Park, Chang-Hyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.12
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    • pp.1705-1710
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    • 2018
  • This paper deals with an analysis of the causes of over current relay(OCR) misoperation in power system with distributed generations(DG). In general, Y-D and Y-Y-D transformer connections are used for grid interconnection of DG. According to the interconnection guideline, the neutral point on Y side should be grounded. However, these transformer connections can lead to OCR misoperation as well as over current ground relay(OCGR) misoperation. Several researches have addressed the OCGR misoperation due to the interaction between transformer connections and zero-sequence voltage of distribution system. Recently, a misoperation of OCR at the point of DG interconnection to the utility system has been also reported. With increasing the interconnections of DG, such OCR as well as OCGR misoperations are expected to increase. In this paper, PSCAD/EMTDC modeling including DG interconnection transformer was performed and various case studies was carried out for identifying the cause of OCR misoperation.

THE HARMONIC ANALYSIS ASSOCIATED TO THE HECKMAN-OPDAM'S THEORY AND ITS APPLICATION TO A ROOT SYSTEM OF TYPE BCd

  • Trimeche, Khalifa
    • Korean Journal of Mathematics
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    • v.27 no.1
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    • pp.221-267
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    • 2019
  • In the five first sections of this paper we define and study the hypergeometric transmutation operators $V^W_k$ and $^tV^W_k$ called also the trigonometric Dunkl intertwining operator and its dual corresponding to the Heckman-Opdam's theory on ${\mathbb{R}}^d$. By using these operators we define the hypergeometric translation operator ${\mathcal{T}}^W_x$, $x{\in}{\mathbb{R}}^d$, and its dual $^t{\mathcal{T}}^W_x$, $x{\in}{\mathbb{R}}^d$, we express them in terms of the hypergeometric Fourier transform ${\mathcal{H}}^W$, we give their properties and we deduce simple proofs of the Plancherel formula and the Plancherel theorem for the transform ${\mathcal{H}}^W$. We study also the hypergeometric convolution product on W-invariant $L^p_{\mathcal{A}k}$-spaces, and we obtain some interesting results. In the sixth section we consider a some root system of type $BC_d$ (see [17]) of whom the corresponding hypergeometric translation operator is a positive integral operator. By using this positivity we improve the results of the previous sections and we prove others more general results.

Reflection and propagation of plane waves at free surfaces of a rotating micropolar fibre-reinforced medium with voids

  • Anya, Augustine Igwebuike;Khan, Aftab
    • Geomechanics and Engineering
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    • v.18 no.6
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    • pp.605-614
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    • 2019
  • The present paper seeks to investigate propagation and reflection of waves at free surfaces of homogeneous, anisotropic and rotating micropolar fibre-reinforced medium with voids. It has been observed that, in particular when P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational wave and a wave due to voids. Normal mode Analysis usually called harmonic solution method is adopted in concomitant with Snell's laws and appropriate boundary conditions in determination of solution to the micropolar fibre reinforced modelled problem. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically. Also, the Reflection Coefficients are presented using numerical simulated results in graphical form for a particular chosen material by the help of Mathematica software. We observed that the micropolar fibre-reinforced, voids and rotational parameters have various degrees of effects to the modulation, propagation and reflection of waves in the medium. The study would have impact to micropolar fibre-reinforecd rotational-acoustic machination fields and future works about behavior of seismic waves.

Comparative Study of Flux Regulation Methods for Hybrid Permanent Magnet Axial Field Flux-switching Memory Machines

  • Yang, Gongde;Fu, Xinghe;Lin, Mingyao;Li, Nian;Li, Hao
    • Journal of Power Electronics
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    • v.19 no.1
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    • pp.158-167
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    • 2019
  • This research comparatively studies three kinds of flux regulation methods, namely, stored capacitor discharge pulse (SCDP), constant current source pulse (CCSP), and quantitative flux regulation pulse (QFRP), which are used for hybrid permanent magnet (PM) axial field flux-switching memory machines (HPM-AFFSMMs). Through an analysis of the operation principle and the series hybrid PM flux regulation mechanism of the objective machine, the circuit topologies and flux regulation process of these flux regulation methods are addressed in detail. On the basis of a simulation, the flux regulation characteristics of the researched machine during the magnetization and demagnetization processes are comparatively evaluated. Then, machine performance, including back EMF, direct and quadrature axis inductances, and magnetization and demagnetization characteristics, is quantitatively investigated. Results show that the QFRP enables the HPM-AFFSMM to achieve a less harmonic component of back EMF by approximately 7.28% and 7.97% at the magnetization and demagnetization states, respectively, and a more complete magnetization process than the SCDP and CCSP.

Instability and vibration analyses of FG cylindrical panels under parabolic axial compressions

  • Kumar, Rajesh;Dey, Tanish;Panda, Sarat K.
    • Steel and Composite Structures
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    • v.31 no.2
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    • pp.187-199
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    • 2019
  • This paper presents the semi-analytical development of the dynamic instability behavior and the dynamic response of functionally graded (FG) cylindrical shallow shell panel subjected to different type of periodic axial compression. First, in prebuckling analysis, the stresses distribution within the panels are determined for respective loading type and these stresses are used to study the dynamic instability behavior and the dynamic response. The prebuckling stresses within the shell panel are the same as applied in-plane edge loading for the case of uniform and linearly varying loadings. However, this is not true for the case of parabolic loadings. The parabolic edge loading produces all the stresses (${\sigma}_{xx}$, ${\sigma}_{yy}$ and ${\tau}_{xy}$) within the FG cylindrical panel. These stresses are evaluated by minimizing the membrane energy via Ritz method. Using these stresses the partial differential equations of FG cylindrical panel are formulated by applying Hamilton's principal assuming higher order shear deformation theory (HSDT) and von-$K{\acute{a}}rm{\acute{a}}n$ non-linearity. The non-linear governing partial differential equations are converted into a set of Mathieu-Hill equations via Galerkin's method. Bolotin method is adopted to trace the boundaries of instability regions. The linear and non-linear dynamic responses in stable and unstable region are plotted to know the characteristics of instability regions of FG cylindrical panel. Moreover, the non-linear frequency-amplitude responses are obtained using Incremental Harmonic Balance (IHB) method.

Single-Stage AC/DC Converter for Wireless Power Transfer Operating With Robustness in Wide Air Gaps (넓은 공극에서 강인성을 가지고 동작하는 단일전력단 무선전력전송 교류-직류 컨버터)

  • Woo, Jeong-Won;Jang, Ki-Chan;Kim, Min-Ji;Kim, Eun-Soo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.2
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    • pp.141-149
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    • 2021
  • In the field of electric vehicles and AGVs, wireless power transfer (WPT) charging systems have been developed recently because of its convenience, reliability, and positive environmental impact due to cable and cord elimination. In this study, we propose a WPT charging system using a single stage AC-DC converter that can be reduced in size and weight and thus can ensure convenience. The proposed single-stage AC-DC converter can control a wide output voltage (36-54 VDC) within coupling ranges by using the variable link voltage applied to the WPT resonant circuit through phase-shifted modulation at a fixed switching frequency. Moreover, the input power factor and total harmonic distortion can be improved by using the proposed converter. A 1 kW prototype that can operate with an air gap range of 40-50 mm is fabricated and validated through experimental results and analysis.

Single Phase Inverter High Frequency Circuit Modeling and Verification for Differential Mode Noise Analysis (차동 노이즈 분석을 위한 단상 인버터 고주파 회로 모델링 및 검증)

  • Shin, Ju-Hyun;Seng, Chhaya;Kim, Woo-Jung;Cha, Hanju
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.3
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    • pp.176-182
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    • 2021
  • This research proposes a high-frequency circuit that can accurately predict the differential mode noise of single-phase inverters at the circuit design stage. Proposed single-phase inverter high frequency circuit in the work is a form in which harmonic impedance components are added to the basic single-phase inverter circuit configuration. For accurate noise prediction, parasitic components present in each part of the differential noise path were extracted. Impedance was extracted using a network analyzer and Q3D in the measurement range of 150 kHz to 30 MHz. A high-frequency circuit model was completed by applying the measured values. Simulations and experiments were conducted to confirm the validity of the high-frequency circuit. As a result, we were able to predict the resonance point of the differential mode voltage extracted as an experimental value with a high-frequency circuit model within an approximately 10% error. Through this outcome, we could verify that differential mode noise can be accurately predicted using the proposed model of the high-frequency circuit without a separate test bench for noise measurement.

Cyclic testing of a new visco-plastic damper subjected to harmonic and quasi-static loading

  • Modhej, Ahmad;Zahrai, Seyed Mehdi
    • Structural Engineering and Mechanics
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    • v.81 no.3
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    • pp.317-333
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    • 2022
  • Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

On the wave propagations of football game ball after contacting with the player foot

  • Lei Sun;Cancan Wei;Fei Liu;Lijun Wang;Bo Ren
    • Geomechanics and Engineering
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    • v.33 no.6
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    • pp.529-542
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    • 2023
  • Wave propagation with high transverse deflection could affect the stability of the ball in its trajectory. For low stiffness balls similar to soccer and volleyball balls, the waves are more noticeable in comparison to other balls like ping-pong ball. On the other hand, the soccer balls are under heavy impact loads from shoots and contacting different objects in the field. The maximum recorded speed of a soccer ball after kicking is the 211 km/hr and the average maximum speed is around 112 km/hr. Therefore, in such speeds the aerodynamic forces become important which are directly related to geometrical shape of the ball. In this regard, the wave propagation in soccer ball is examined in the current study using large deformation shear deformable formulations. Classical relations of stress-strain components are taken into consideration along with minimum total energy principle. The final derived relations were solved by using harmonic differential quadrature method. The results are generally presented ion term of phase velocity as function of different influencing parameters of the materials, geometry and mass of the ball.

Studies on control mechanism and performance of a novel pneumatic-driven active dynamic vibration absorber

  • Kunjie Rong;Xinghua Li;Zheng Lu;Siyuan Wu
    • Structural Engineering and Mechanics
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    • v.87 no.2
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    • pp.117-127
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    • 2023
  • To efficiently attenuate seismic responses of a structure, a novel pneumatic-driven active dynamic vibration absorber (PD-ADVA) is proposed in this study. PD-ADVA aims to realize closed-loop control using a simple and intuitive control algorithm, which takes the structure velocity response as the input signal and then outputs an inverse control force to primary structure. The corresponding active control theory and phase control mechanism of the system are studied by numerical and theoretical methods, the system's control performance and amplitude-frequency characteristics under seismic excitations are explored. The capability of the proposed active control system to cope with frequency-varying random excitation is evaluated by comparing with the optimum tuning TMD. The analysis results show that the control algorithm of PD-ADVA ensures the control force always output to the structure in the opposite direction of the velocity response, indicating that the presented system does not produce a negative effect. The phase difference between the response of uncontrolled and controlled structures is zero, while the phase difference between the control force and the harmonic excitation is π, the theoretical and numerical results demonstrate that PD-ADVA always generates beneficial control effects. The PD-ADVA can effectively mitigate the structural seismic responses, and its control performance is insensitive to amplitude. Compared with the optimum tuning TMD, PD-ADVA has better control performance and higher system stability, and will not have negative effects under seismic wave excitations.