Showing papers on "Transient (oscillation) published in 2012"
TL;DR: Simulation studies indicate that the proposed MPC supervisory strategy considering diesel engine transient characteristics possesses superior equivalent fuel efficiency while maintaining HEV driving performance.
Abstract: This paper presents a model predictive control (MPC) torque-split strategy that incorporates diesel engine transient characteristics for parallel hybrid electric vehicle (HEV) powertrains. To improve HEV fuel efficiency, torque split between the diesel engine and the electric motor and the decision as to whether the engine should be on or off are important. For HEV applications where the engines experience frequent transient operations, including start-stop, the effect of the engine transient characteristics on the overall HEV powertrain fuel economy becomes more pronounced. In this paper, by incorporating an experimentally validated real-time-capable transient diesel-engine model into the MPC torque-split method, the engine transient characteristics can be well reflected on the HEV powertrain supervisory control decisions. Simulation studies based on an HEV model with actual system parameters and an experimentally validated diesel-engine model indicate that the proposed MPC supervisory strategy considering diesel engine transient characteristics possesses superior equivalent fuel efficiency while maintaining HEV driving performance.
191 citations
TL;DR: The experimental demonstration of a hybrid optoelectronic neuromorphic computer based on a complex nonlinear wavelength dynamics including multiple delayed feedbacks with randomly defined weights successfully evaluated on a standard benchmark test.
Abstract: We report on the experimental demonstration of a hybrid optoelectronic neuromorphic computer based on a complex nonlinear wavelength dynamics including multiple delayed feedbacks with randomly defined weights. This neuromorphic approach is based on a new paradigm of a brain-inspired computational unit, intrinsically differing from Turing machines. This recent paradigm consists in expanding the input information to be processed into a higher dimensional phase space, through the nonlinear transient response of a complex dynamics excited by the input information. The computed output is then extracted via a linear separation of the transient trajectory in the complex phase space. The hyperplane separation is derived from a learning phase consisting of the resolution of a regression problem. The processing capability originates from the nonlinear transient, resulting in nonlinear transient computing. The computational performance is successfully evaluated on a standard benchmark test, namely, a spoken digit recognition task.
170 citations
TL;DR: In this paper, a new transient harmonic current protection scheme is proposed, which can not only identify internal faults and external faults correctly and quickly, but also can respond to high ground resistance faults.
Abstract: Based on the boundary characteristic of a dc transmission line, the response of transient harmonic current in the line-commutated converter HVDC transmission system is analyzed under various fault conditions in this paper. A new transient harmonic current protection scheme is proposed. The discrete Fourier transform is used to extract transient harmonic currents at both terminals of the dc transmission line and the type of fault can be identified by the transient harmonic currents. Two main factors including fault resistance and fault location that affect performance of the protection are also discussed in this study. The test system is modeled based on the CIGRE benchmark including distributed parameters of the dc transmission line. Comprehensive test studies show that the performance of the transient harmonic current protection scheme is encouraging. It can not only identify internal faults and external faults correctly and quickly, but also can respond to high ground resistance faults.
162 citations
TL;DR: In this article, the authors proposed transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation.
Abstract: Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation. This study uses the wavelet transform (WT) of the time-frequency domain to analyze and detect the transient physical behavior of loads during the load identification. The experimental results show the transient response time and transient energy are better than the steady-state features to improve the recognition accuracy and reduces computation requirements in non-intrusive load monitoring (NILM) systems. The discrete wavelet transform (DWT) is more suitable than short-time Fourier transform (STFT) for transient load analyses.
149 citations
TL;DR: In this paper, the authors proposed a fault detection algorithm based on the traveling-wave principle, which relies on the fault-generated surge arrival times at two ends of the dc line as inputs.
Abstract: This paper presents a novel algorithm to determine the location of dc line faults in an HVDC system with a mixed transmission media consisting of overhead lines and cables, using only the measurements taken at the rectifier and inverter ends of the composite transmission line. The algorithm relies on the traveling-wave principle, and requires the fault-generated surge arrival times at two ends of the dc line as inputs. With accurate surge arrival times obtained from time-synchronized measurements, the proposed algorithm can accurately predict the faulty segment as well as the exact fault location. Continuous wavelet transform coefficients of the input signal are used to determine the precise time of arrival of traveling waves at the dc line terminals. Two possible input signals-the dc voltage measured at the converter terminal and the current through the surge capacitors connected at the dc line end-are examined and both signals are found to be equally effective for detecting the traveling-wave arrival times. Performance of the proposed fault-location scheme is analyzed through detailed simulations carried out using the electromagnetic transient simulation software PSCAD. The impact of measurement noise on the fault-location accuracy is also studied in this paper.
147 citations
TL;DR: An intelligent wide area synchrophasor based system (IWAS) for predicting and mitigating transient instabilities is proposed that incorporates artificial neural networks (ANN) for transient stability prediction.
Abstract: Increasing expansion of power systems and grids are accompanied nowadays by innovation in smart grid solutions to maintain systems stability. This paper proposes an intelligent wide area synchrophasor based system (IWAS) for predicting and mitigating transient instabilities. The IWAS incorporates artificial neural networks (ANN) for transient stability prediction. The ANN makes use of the advent of phasor measurements units (PMU) for real-time prediction. Coherent groups of generators-which swing together-is identified through an algorithm based on PMU measurements. A remedial action scheme (RAS) is applied to counteract the system instability by splitting the system into islands and initiate under frequency load shedding actions. The potential of the proposed approach is tested using New England 39 bus system.
136 citations
TL;DR: In this paper, the authors proposed a fault location algorithm for dc line faults in HVDC systems with multiple terminals connected to a common point, using only the measurements taken at the converter stations.
Abstract: This paper presents a novel algorithm to determine the location of dc line faults in an HVDC system with multiple terminals connected to a common point, using only the measurements taken at the converter stations. The algorithm relies on the traveling-wave principle, and requires the fault-generated surge arrival times at the converter terminals. With accurate surge arrival times obtained from time-synchronized measurements, the proposed algorithm can accurately predict the faulty segment as well as the exact fault location. Continuous wavelet transform coefficients of the input signal are used to determine the precise time of arrival of traveling waves at the dc line terminals. Performance of the proposed fault-location scheme is analyzed through detailed simulations carried out using the electromagnetic transient simulation software PSCAD. The algorithm does not use reflected waves for its calculations and therefore it is more robust compared to fault location algorithms previously proposed for teed transmission lines. Furthermore, the algorithm can be generalized to handle any number of line segments connected to the star point.
132 citations
TL;DR: In this article, a new transient energy protection scheme is proposed based on the distributed parameter line model in which the transient energy distribution over the line can be obtained from the voltage and current measurements at both terminals and the fault can be recognized from the calculated value simply.
Abstract: The relation between the parameters of dc transmission line and the variation of transient energy has been analyzed under various fault conditions in this paper. According to that, a new transient energy protective scheme is proposed. It is developed based on the distributed parameter line model in which the transient energy distribution over the line can be obtained from the voltage and current measurements at both terminals and the fault can be recognized from the calculated value simply. The test system is modeled based on the CIGRE benchmark and considered the distributed parameters of the dc transmission line. Comprehensive test studies show that the performance of transient energy protection scheme is encouraging. It can not only identify internal fault and external faults correctly and quickly, but can also respond to the high ground resistance fault. Finally, two main factors, including fault resistance and transmission distance, that affect the performance of the protection are also discussed.
120 citations
TL;DR: The impact of the phasor estimation models on the accuracy of these devices, focuses on algorithms proposed in the literature for the estimation of dynamic phasors, and studies their performances under several different conditions.
Abstract: Phasor measurement units (PMUs) are becoming one of the key issues of power network monitoring. They have to be able to perform accurate estimations of quantities of interest either under steady-state or transient conditions. Among all the sources which may contribute to the uncertainty introduced by PMUs, this paper analyzes the impact of the phasor estimation models on the accuracy of these devices, focuses on algorithms proposed in the literature for the estimation of dynamic phasors, and studies their performances under several different conditions.
119 citations
TL;DR: In this article, the authors proposed a new control scheme for doubly fed induction generator (DFIG)-based WPPs to fulfill the Australian grid code requirements, which requires wind generators to ride-through severe low and high-voltage conditions, provide reactive power support during the fault period, and exhibits fast power recovery after the supply voltage restoration.
Abstract: Australian Grid Code has recently enforced stringent regulations on the transient response of large wind power plants (WPPs). The new grid code requires wind generators to ride-through severe low- and high-voltage conditions, provides reactive power support during the fault period, and exhibits fast power recovery after the supply voltage restoration. This paper proposes a new control scheme for doubly fed induction generator (DFIG)-based WPPs to fulfill these requirements in one inclusive approach. New design strategies for the outer power control loops of DFIG are suggested and their corresponding P-Q capability curves are rigorously studied. It is shown that safely overloaded converters can enhance the reactive power capability of DFIGs during the fault periods. Moreover, for the inner current control loops, the conventional PI current regulators are replaced with enhanced hysteresis-based current regulators. This current regulator, with very fast transient response, increases low- and high-voltage ride-through capabilities of the DFIG, as requested by the Australian Grid Code. Finally, time-domain simulation studies are conducted to evaluate the capability of the proposed control scheme to fulfill the Australian regulations and examine its positive impacts on the transient response of the adjacent fixed-speed WPP.
107 citations
TL;DR: In this paper, a phase-controlled laser-induced transient thermal grating technique for noncontact, non-destructive measurements of thermal transport in opaque material is presented, where the phase grating signal includes components associated with both transient reflectivity and surface displacement.
Abstract: The methodology for a heterodyned laser-induced transient thermal grating technique for non-contact, non-destructive measurements of thermal transport in opaque material is presented. Phase-controlled heterodyne detection allows us to isolate pure phase or amplitude transient grating signal contributions by varying the relative phase between reference and probe beams. The phase grating signal includes components associated with both transient reflectivity and surface displacement whereas the amplitude grating contribution is governed by transient reflectivity alone. By analyzing the latter with the two-dimensional thermal diffusion model, we extract the in-plane thermal diffusivity of the sample. Measurements on a 5 μm thick single crystal PbTe film yielded excellent agreement with the model over a range of grating periods from 1.6 to 2.8 μm. The measured thermal diffusivity of 1.3 × 10−6 m2/s was found to be slightly lower than the bulk value.
TL;DR: A novel control scheme for the fast current control of permanent magnet synchronous machines that mainly works in the transient state of current control without deteriorating steady-state characteristics is proposed.
Abstract: This paper proposes a novel control scheme for the fast current control of permanent magnet synchronous machines. The proposed method mainly works in the transient state of current control without deteriorating steady-state characteristics. The proposed method is applicable in a wide range of speed: in the speed below the base speed and in the flux weakening region. Using the proposed method, the reference values of currents are modified so that the currents follow the so-called “shortcut” trajectory in the coordinate plane. The effectiveness of the proposed method is confirmed by computer simulations and experiments. The settling time is reduced by 55% compared with that of the conventional method.
TL;DR: A dc arc model derived from a hyperbolic approximation of observed arc voltage and current patterns, which permit analyzing the arc in terms of its resistance, power, energy, and quenching condition is presented.
Abstract: This paper presents a dc arc model to simplify the study of a critical issue in dc microgrids: series faults. The model is derived from a hyperbolic approximation of observed arc voltage and current patterns, which permit analyzing the arc in terms of its resistance, power, energy, and quenching condition. Recent faults staged by the authors on a dc microgrid yielded enough data to develop an arc model for three fault types: constant-gap speed, fixed-gap distance, and accelerated gap. The results in this paper compare experimental and simulation results for the three fault types. It is concluded that because the instantaneous voltage, current, power, and energy waveforms produced by the model agree well with experimental results, the model is suitable for transient simulations.
TL;DR: In this paper, the authors suggest a precursor to the loss of transient stability in multi-machine power systems based on the discovery of [Y. Susuki, I. Mezic, and T. Hikihara, 2011].
Abstract: We suggest a precursor to phenomena of loss of transient stability in multi-machine power systems. This precursor is based on discovery of [Y. Susuki, I. Mezic , and T. Hikihara, J. Nonlinear Sci., vol. 21, no. 3, pp. 403-439, June 2011], an emergent transmission path of energy from many oscillatory modes to one oscillatory mode that represents an instability phenomenon of interest. The pathway from high frequency modes to the lowest frequency mode is called the coherent swing instability (CSI). The modes are extracted from sensor data or data provided by simulation outputs of power system oscillations by using the Koopman mode analysis that is based on a fully nonlinear spectral theory and represents an extension of linear oscillatory mode analysis. The CSI transmission path is identified by computation of the so-called action transfer operator that is derived by refining a mathematical model of transient stability using the Koopman mode analysis. This provides a new technique for monitoring the loss of transient stability by a combination of practical data, mathematical modeling, and computation.
TL;DR: The new method proposed in this paper addresses both problems using the Gabor analysis of the current via the chirp z-transform, which can be easily adapted to generate high-resolution time-frequency stamps of different types of faults.
Abstract: Time-frequency analysis of the transient current in induction motors (IMs) is the basis of the transient motor current signature analysis diagnosis method. IM faults can be accurately identified by detecting the characteristic pattern that each type of fault produces in the time-frequency plane during a speed transient. Diverse transforms have been proposed to generate a 2-D time-frequency representation of the current, such as the short time Fourier transform (FT), the wavelet transform, or the Wigner-Ville distribution. However, a fine tuning of their parameters is needed in order to obtain a high-resolution image of the fault in the time-frequency domain, and they also require a much higher processing effort than traditional diagnosis techniques, such as the FT. The new method proposed in this paper addresses both problems using the Gabor analysis of the current via the chirp z-transform, which can be easily adapted to generate high-resolution time-frequency stamps of different types of faults. In this paper, it is used to diagnose broken bars and mixed eccentricity faults of an IM using the current during a startup transient. This new approach is theoretically introduced and experimentally validated with a 1.1-kW commercial motor in faulty and healthy conditions.
TL;DR: In this paper, a numerical transient three-dimensional heat transfer investigation of a hybrid PCM-based heat sink cooling technique was presented, where the n -eicosane was adopted inside the heat sink cavity as the Phase Change Material (PCM) for latent heat storage.
12 Nov 2012
TL;DR: In this paper, the authors investigated the transient magnetic behavior of an interior permanent magnet (IPM) synchronous machine following a large transient current caused by a fault condition using finite element analysis and numerical integration.
Abstract: This paper investigates the transient magnetic behavior of an interior permanent magnet (IPM) synchronous machine following a large transient current caused by a fault condition. A combination of finite element (FE) analysis and numerical integration of the machine equations is used to calculate the currents resulting from a symmetrical three-phase short-circuit fault at the machine terminals, including magnetic saturation effects. FE analysis is further used to simulate the magnetic behavior of the machine when subjected to the fault currents, with a particular focus on the propagation of the demagnetizing MMF throughout the conductive laminations as well as the conductive PM material. Eddy currents induced in the laminations and magnet material are shown to impede the progression of the demagnetizing MMF. However, the transient analysis illustrates the manner in which the fault currents ultimately trigger the onset of irreversible demagnetization of significant portions of the rotor magnets in the analyzed machine. The transient demagnetization analysis method is extended to investigate the influence of several key design variables, including machine operating temperature and segmentation of the rotor magnets.
Patent•
12 Oct 2012TL;DR: In this paper, the authors present various embodiment of systems and methods for calculating a fault location in electric power delivery system based on a traveling wave created by an electrical fault in the EPC system.
Abstract: Disclosed herein are various embodiments of systems and methods for calculating a fault location in electric power delivery system based on a traveling wave created by an electrical fault in the electric power delivery system. According to one embodiment, an intelligent electronic device may be configured to detect a transient traveling wave caused by an electrical fault. A first traveling wave value of the transient traveling wave may be determined and a corresponding first time associated with the first traveling wave may be determined. The IED may receive a second time associated with a second traveling wave value of the transient traveling wave detected by a remote IED. The distance to the remote IED may be known. An estimated fault location may be generated based on the time difference between the first time and the second time. Additional methods of calculating the fault location may also be employed.
TL;DR: In this article, the authors present the average-value modeling methodologies for the conventional three-phase (six-pulse) front-end rectifier loads, and demonstrate the system operation and dynamic performance of the developed average models in discontinuous and continuous modes, as well as under balanced and unbalanced operation.
Abstract: Electric power distribution systems of many commercial and industrial sites often employ variable frequency drives and other loads that internally utilize dc. Such loads are often based on front-end line-commutated rectifiers. The detailed switch-level models of such rectifier systems can be readily implemented using a number of widely available digital programs and transient simulation tools, including the Electromagnetic Transient (EMT)-based programs and Matlab/Simulink. To improve the simulation efficiency for the system-level transient studies with a large number of such subsystems, the so-called dynamic average models have been utilized. This paper presents the average-value modeling methodologies for the conventional three-phase (six-pulse) front-end rectifier loads. We demonstrate the system operation and the dynamic performance of the developed average models in discontinuous and continuous modes, as well as under balanced and unbalanced operation.
TL;DR: In this paper, a 3D FEM model is presented to predict the thermal behavior of a high speed motor spindle, which considers complex boundary conditions like heat sources as well as contact and convective heat transfer between spindle parts.
TL;DR: In this paper, a nonlinear sliding mode observer for the synchronous machine damper currents is constructed, and the stabilizing feedback laws for the complete nine order model of a power system, which takes into account the stator dynamics as well as the damper effects, are developed.
TL;DR: Simulation results show that adequately modelling the DC voltage droop characteristics or a distributed voltage control in both the powerfiow algorithm and in the transient stability models allows to simulate the steady-state results of the dynamic simulation by means of power flow software algorithms.
TL;DR: In this article, a GA-based method for the aggregation of a mixed wind farm with different wind turbine generator system (WTGS) parameters is proposed and validated, and the transient performances of a grid-connected wind farm including the output active power and the output voltage are investigated by using the proposed method.
22 Jul 2012
TL;DR: In this paper, the authors proposed an algorithm to determine the location of DC line faults in an HVDC system with a mixed transmission media consisting of overhead lines and cables, using only the measurements taken at the rectifier and inverter ends of the composite transmission line.
Abstract: Summary form only given. This paper presents a novel algorithm to determine the location of DC line faults in an HVDC system with a mixed transmission media consisting of overhead lines and cables, using only the measurements taken at the rectifier and inverter ends of the composite transmission line. The algorithm relies on the travelling wave principle, and requires the fault generated surge arrival times at two ends of the DC line as inputs. With accurate surge arrival times obtained from time synchronized measurements, the proposed algorithm can accurately predict the faulty segment as well as the exact fault location. Continuous wavelet transform coefficients of the input signal are used to determine the precise time of arrival of travelling waves at the DC line terminals. Two possible input signals, the DC voltage measured at the converter terminal and the current through the surge capacitors connected at the DC line end, are examined and both signals are found to be equally effective for detecting the travelling wave arrival times. Performance of the proposed fault-location scheme is analyzed through detailed simulations carried out using the electromagnetic transient simulation software PSCAD®. The impact of measurement noise on the fault location accuracy is also studied in the paper.
TL;DR: In this paper, a transient thermal measurement system was developed to investigate the transient thermal behavior of insulated-gate bipolar transistor (IGBT) modules attached by nanosilver paste and two kinds of lead-free solders.
Abstract: Recently, to accurately study the transient thermal behavior of power modules, a transient thermal measurement system was developed to investigate the transient thermal behavior of insulated-gate bipolar transistor (IGBT) modules attached by nanosilver paste and two kinds of lead-free solders. We found that the transient thermal impedance of IGBT modules attached by nanosilver paste was 9% lower than that of the modules using SAC305 and SN100C with 40-ms heating pulse. In addition, finite-element analysis is employed to simulate thermal performance of the IGBT devices. The simulation shows that the transient thermal impedance of IGBT modules attached by nanosilver paste was also lower than that of the modules using lead-free solders. A convenient way was introduced to well predict the transient thermal behavior of IGBT power module. The calculated results agreed well with the measured one. The interface thermal impedance of sintered nanosilver and SNC100C are calculated to be 0.011 ~ 0.031 K/W and 0.022 ~ 0.042 K/W, respectively.
TL;DR: In this article, a current-error space-vector-based hysteresis controller with online computation of boundary for two-level inverter-fed induction motor (IM) drives is proposed.
Abstract: This paper proposes a current-error space-vector-based hysteresis controller with online computation of boundary for two-level inverter-fed induction motor (IM) drives. The proposed hysteresis controller has got all advantages of conventional current-error space-vector-based hysteresis controllers like quick transient response, simplicity, adjacent voltage vector switching, etc. Major advantage of the proposed controller-based voltage-source-inverters-fed drive is that phase voltage frequency spectrum produced is exactly similar to that of a constant switching frequency space-vector pulsewidth modulated (SVPWM) inverter. In this proposed hysteresis controller, stator voltages along α- and β-axes are estimated during zero and active voltage vector periods using current errors along α- and β-axes and steady-state model of IM. Online computation of hysteresis boundary is carried out using estimated stator voltages in the proposed hysteresis controller. The proposed scheme is simple and capable of taking inverter upto six-step-mode operation, if demanded by drive system. The proposed hysteresis-controller-based inverter-fed drive scheme is experimentally verified. The steady state and transient performance of the proposed scheme is extensively tested. The experimental results are giving constant frequency spectrum for phase voltage similar to that of constant frequency SVPWM inverter-fed drive.
01 Jun 2012
TL;DR: In this paper, a particular case of the Wilson-Daubechies time-frequency transform for use in the gravitational-wave burst analysis was considered, where the spectral leakage control of the frequency subbands and the existence of the analytic time-delay filters were considered.
Abstract: The time-frequency transforms are important tools for identification of transient events in the output of the gravitational-wave detectors. Produced by the terrestrial and possibly by astrophysical sources, the transient events can be identified as patterns on the time-frequency plane with the excess power above stationary detector noise. In this paper we consider a particular case of the Wilson-Daubechies time-frequency transform for use in the gravitational-wave burst analysis. The presented Wilson-Daubechies basis shares some properties with the Gabor frames, but circumvents the Balian-Low theorem. It also shares similarity with the Meyer wavelet, which is actively used in the gravitational-wave burst analysis. The main advantages of the Wilson-Daubechies transform are the low computational cost, spectral leakage control, flexible structure of the frequency sub-bands, and the existence of the analytic time-delay filters, which are important for localization of the gravitational-wave sources in the sky. These properties of the Wilson-Daubechies transform may prove useful not only in the transient analysis, but also in other areas of the gravitational wave data analysis and detector characterization.
Posted Content•
TL;DR: The use of magnetic pulses to inject transient faults into the calculations of a RISC micro-controller running the AES algorithm is considered, which proves to be constant (i.e. data independent) under certain experimental conditions.
Abstract: This article considers the use of magnetic pulses to inject transient faults into the calculations of a RISC micro-controller running the AES algorithm. A magnetic coil is used to generate the pulses. It induces computational faults without any physical contact with the device. The injected faults are proved to be constant (i.e. data independent) under certain experimental conditions. This behaviour, combined with the ability to choose the faulted bytes thanks to timing accuracy in the fault injection process, makes it possible to implement most of the state-of-the-art fault attack schemes.
TL;DR: In this article, a detailed experimental investigation of G550 steel with a thickness of 1mm under both transient and steady state test methods is discussed, and the results show that the steady state method is not equivalent to the transient state method for G 550 steel.
TL;DR: In this article, a time-domain harmonic balance method is derived and adapted to phase lag periodic conditions to allow the simulation of only one blade passage per row regardless of row blade counts.
Abstract: In the absence of instabilities, the large deterministic scales of turbomachinery flows resulting from the periodic rotation of blades can be considered periodic in time. Such flows are not simulated with enough efficiency when using classical unsteady techniques as a transient regime must be bypassed. New techniques, dedicated to time-periodic flows and based on Fourier analysis, have been developed recently. Among these, harmonic balance methods cast a time-periodic flow computation in several coupled steady flow computations. A time-domain harmonic balance method is derived and adapted to phase lag periodic conditions to allow the simulation of only one blade passage per row regardless of row blade counts. Sophisticated space and time interpolations are involved and detailed. The test case is a single stage subsonic compressor. A convergence study of the present harmonic balance is performed and compared with a reference well-resolved classical unsteady flow simulation. The results show, on one hand, the good behavior of the harmonic balance and its ability to correctly predict global quantities as well as local flow pattern; on the other hand, the simulation time is drastically reduced.