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Showing papers on "Transient (oscillation) published in 2016"


Journal ArticleDOI
TL;DR: Transient technology is an emerging field that requires materials, devices, and systems to be capable of disappearing with minimal or non-traceable remains over a period of stable operation.
Abstract: Transient technology is an emerging field that requires materials, devices, and systems to be capable of disappearing with minimal or non-traceable remains over a period of stable operation. Electronics with the capability of disintegrating or vanishing after stable operation are becoming an interesting research topic and have attracted increasing attentions. In recent years, transience technology has been extended to intelligence applications, bioelectronics and environmental monitoring systems, and energy harvesters and storage. Although the transient concept has only a few years of development, this emerging transient technology is believed to find more opportunities in the fast development of advanced electronics. In this review, we will examine recent progress in the development of transient electronics. First, an overview of various transient materials, including metals, polymers, and semiconductor materials, is described. Second, recent progress in the design and development of transient electronic...

249 citations


Journal ArticleDOI
TL;DR: The proposed generalized model proves to be accurate for angle and voltage stability analysis, as it includes a balanced, fundamental-frequency model of the voltage source converter (VSC) and the dynamics of the dc link.
Abstract: This paper presents a generalized energy storage system model for voltage and angle stability analysis. The proposed solution allows modeling most common energy storage technologies through a given set of linear differential algebraic equations (DAEs). In particular, the paper considers, but is not limited to, compressed air, superconducting magnetic, electrochemical capacitor and battery energy storage devices. While able to cope with a variety of different technologies, the proposed generalized model proves to be accurate for angle and voltage stability analysis, as it includes a balanced, fundamental-frequency model of the voltage source converter (VSC) and the dynamics of the dc link. Regulators with inclusion of hard limits are also taken into account. The transient behavior of the generalized model is compared with detailed fundamental-frequency balanced models as well as commonly-used simplified models of energy storage devices. A comprehensive case study based on the WSCC 9-bus test system is presented and discussed.

149 citations


Journal ArticleDOI
TL;DR: In this paper, a small-signal model based on dynamic phasors is introduced which takes into consideration the dynamics of internal variables, such as circulating arm currents, which have a tendency for a large second harmonic component and module capacitor voltage ripple, which has other harmonic components.
Abstract: This paper reveals the existence of poorly damped resonant modes in the modular multilevel converter (MMC) that can result in harmonic instability. A small-signal model based on dynamic phasors is introduced which takes into consideration the dynamics of internal variables, such as circulating arm currents, which have a tendency for a large second harmonic component and module capacitor voltage ripple, which has other harmonic components. The small-signal model is validated by comparison with the electromagnetic transient simulation of a detailed model. It is shown that the use of an active circulating current suppressing scheme can effectively improve the damping of internal harmonic modes in comparison with a passive filter used for the same purpose. The damping of internal harmonic modes has been shown to be significantly impacted by the gains of the MMC's outer-loop controller but is less sensitive to the ac system strength or the gain of the phase-locked loop. A larger arm resistance also increases the damping of these internal modes.

145 citations


Journal ArticleDOI
15 Sep 2016-Energy
TL;DR: In this article, the electrical power and energy of fractional-order capacitance and inductance were derived in both steady-state and transient conditions, and verified using a number of commercial supercapacitors and fractionalorder coils.

101 citations


Journal ArticleDOI
TL;DR: A combined theoretical and experimental study is presented of a harvester configuration that utilizes the motion of a levitated hard-magnetic element to generate electrical power and a semi-analytical, non-linear model is introduced that enables accurate and efficient analysis of energy transduction.
Abstract: Magnetic levitation has been used to implement low-cost and maintenance-free electromagnetic energy harvesting. The ability of levitation-based harvesting systems to operate autonomously for long periods of time makes them well-suited for self-powering a broad range of technologies. In this paper, a combined theoretical and experimental study is presented of a harvester configuration that utilizes the motion of a levitated hard-magnetic element to generate electrical power. A semi-analytical, non-linear model is introduced that enables accurate and efficient analysis of energy transduction. The model predicts the transient and steady-state response of the harvester a function of its motion (amplitude and frequency) and load impedance. Very good agreement is obtained between simulation and experiment with energy errors lower than 14.15% (mean absolute percentage error of 6.02%) and cross-correlations higher than 86%. The model provides unique insight into fundamental mechanisms of energy transduction and enables the geometric optimization of harvesters prior to fabrication and the rational design of intelligent energy harvesters.

93 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a transient thermal model for IGBT junction temperature simulations during short circuits or overloads using finite element method (FEM) thermal simulations with temperature-dependent physical parameters.
Abstract: A basic challenge in the insulated gate bipolar transistor (IGBT) transient simulation study is to obtain the realistic junction temperature, which demands not only accurate electrical simulations but also precise thermal impedance. This paper proposed a transient thermal model for IGBT junction temperature simulations during short circuits or overloads. The updated Cauer thermal model with varying thermal parameters is obtained by means of finite-element method (FEM) thermal simulations with temperature-dependent physical parameters. The proposed method is applied to a case study of a 1700 V/1000 A IGBT module. Furthermore, a testing setup is built up to validate the simulation results, which is composed of a IGBT baseplate temperature control unit, an infrared camera with a maximum of 3 kHz sampling frequency, and a black-painted open IGBT module.

90 citations


Journal ArticleDOI
TL;DR: A novel centroid-based diagnostic method of the power switches in five-leg voltage source inverter is proposed to provide a simple and robust diagnostic process for switches fault regardless of the shape of the back electromotive forces and the transient states due to the load variation.
Abstract: A novel centroid-based diagnostic method of the power switches in five-leg voltage source inverter is proposed in this paper. Using a vectorial multimachine description, a five-phase drive presenting an opened switch or an opened phase faults has typical operating characteristics in comparison to classical three-phase drives. Based on such characteristics, this paper aims to provide a simple and robust diagnostic process for switches fault regardless of the shape of the back electromotive forces (harmonic components) and the transient states due to the load variation. Original theoretical developments are presented. Experimental results are shown to validate the proposed strategy.

84 citations


Journal ArticleDOI
TL;DR: In this paper, a single phase multilevel inverter configuration that conjoins three series connected full bridge inverters and a single half bridge inverter for renewable energy application especially photo-voltaic system was proposed.

84 citations


Journal ArticleDOI
TL;DR: In this article, a nonlinear dynamic transfer coefficients of the hydro-turbine were proposed by utilizing internal characteristics and analyzing the change laws of the characteristic parameters of the Hydro-Turbine governing system.

77 citations


Journal ArticleDOI
TL;DR: In this paper, a scaled current tracking control for rotor-side converter (RSC) is proposed to enhance its low voltage ride-through capacity without flux observation, which can suppress overcurrent and overvoltage.
Abstract: For doubly fed induction generator (DFIG)-based wind turbine, the main constraint to ride-through serious grid faults is the limited converter rating. In order to realize controllable low voltage ride through (LVRT) under the typical converter rating, transient control reference usually need to be modified to adapt to the constraint of converter's maximum output voltage. Generally, the generation of such reference relies on observation of stator flux and even sequence separation. This is susceptible to observation errors during the fault transient; moreover, it increases the complexity of control system. For this issue, this paper proposes a scaled current tracking control for rotor-side converter (RSC) to enhance its LVRT capacity without flux observation. In this method, rotor current is controlled to track stator current in a certain scale. Under proper tracking coefficient, both the required rotor current and rotor voltage can be constrained within the permissible ranges of RSC, thus it can maintain DFIG under control to suppress overcurrent and overvoltage. Moreover, during fault transient, electromagnetic torque oscillations can be greatly suppressed. Based on it, certain additional positive-sequence item is injected into rotor current reference to supply dynamic reactive support. Simulation and experimental results demonstrate the feasibility of the proposed method.

76 citations


Journal ArticleDOI
TL;DR: A technique to convert the nonlinear equations to a specific control system and use a look-up table, integral controllers and a decoupling controller to help the system converge to a zero-error steady state is presented.
Abstract: Applying the selective harmonic elimination (SHE) technique to grid-connected-cascaded modular multilevel inverters has been widely discussed in the literature. However, due to the difficulties of solving high-order nonlinear transcendental equations, the SHE technique cannot be implemented in real time so its applications are limited. This paper presents a technique to convert the nonlinear equations to a specific control system and use a look-up table, integral controllers and a decoupling controller to help the system converge to a zero-error steady state. An inner instantaneous observer is introduced to directly extract the harmonic spectrum of the output voltages without applying FFT algorithm to output step voltage waveforms. It can not only simplify software design but also eliminate the phase delay generated by conventional spectrum extracting algorithm. The proposed technique can achieve an accurate switching angle control and a fast response. Simulation and experimental results verified that the system can achieve zero-error steady state within one line period.

Journal ArticleDOI
Ke Yan1, Jun Hong1, Jinhua Zhang1, Mi Wei1, Wenwu Wu1 
TL;DR: In this paper, a thermal network approach was developed for spindle transient analysis in consideration of thermal-structure interaction, and the radial and axial deformation of spindle system during assembling process, deformation by thermal extension and centrifugal effect were all obtained.

Journal ArticleDOI
TL;DR: In this paper, applied numerical techniques and flow modeling approaches to simulate the hydraulic turbines are discussed, and the performance of the applied numerical models and turbulence modeling with respect to the operating conditions are discussed.
Abstract: Applications of computational fluid dynamic (CFD) techniques to hydropower have increased rapidly in the last three decades. The majority of the experimental investigations of hydraulic turbines were supported by numerical studies and this has become a standard practice. In the paper, applied numerical techniques and flow modeling approaches to simulate the hydraulic turbines are discussed. Both steady-state and transient operating conditions of the turbines are considered for the review. The steady-state conditions include the best efficiency point (BEP), high load (HL), and part load (PL). The transient conditions include load variation, startup, shutdown, and total load rejection. The performance of the applied numerical models and turbulence modeling with respect to the operating conditions are discussed. The recently developed numerical technique (transient blade row modeling) using the Fourier transformation (FT) method is discussed. This technique allows guide vane and blade passages to be modeled with the pitch ratio other than unity. Numerical modeling and simulation of hydraulic turbines during the transient operating conditions is one of the most challenging tasks because guide vanes' angular movement is time-dependent and mesh should be dynamic/moving. Different approaches applied to simulate the transient conditions and their limitations are discussed. Overall, this review summarizes the role of numerical techniques, advantages, limitations, and upcoming challenges within hydropower.

Journal ArticleDOI
TL;DR: In this article, a new EMT-transient stability (TS) hybrid simulation platform and its application to a detailed fault-induced delayed voltage recovery (FIDVR) study on the WECC system is presented.
Abstract: This paper deals with the development of a new electromagnetic transient (EMT)-transient stability (TS) hybrid simulation platform and its application to a detailed fault-induced delayed voltage recovery (FIDVR) study on the WECC system A new EMT-TS hybrid simulation platform, which integrates PSCAD/EMTDC and the open source power system simulation software InterPSS has been developed A combined interaction protocol with an automatic protocol switching control scheme is proposed A multi-port three-phase Thevenin equivalent is developed for representing an external network in an EMT simulator Correspondingly, the external network is represented in three-sequence, and a three-sequence TS simulation algorithm is developed These techniques allow simulation of unsymmetrical faults within the internal network without the constraint of phase balance at the boundary The effectiveness of the proposed techniques is first tested on the IEEE 9-bus system Subsequently, the proposed hybrid simulation approach is applied to a detailed FIDVR study on a large WECC system The study shows that a normally cleared single-line-to-ground (SLG) fault in the transmission system could lead to an FIDVR event, with compressor motors of the air conditioning units on the faulted phases stalling first, followed by a propagation of motor stalling to the unfaulted phase Moreover, similar events are observed in simulations with a wide range of load compositions Lastly, the effect of the point-on-wave (POW) at which a fault is applied on the occurrence of an FIVDR event is also analyzed

Journal ArticleDOI
TL;DR: In this article, a supercapacitor type ESS was used in transient state analysis of a grid connected wind turbine in order to enhance low voltage ride through (LVRT) capability.

Journal ArticleDOI
TL;DR: In this paper, a new approach to 3D transient thermal analysis for additive manufacturing for 3D complex industrial structures with freeform features in powder bed systems using laser heat source is introduced.
Abstract: Additive layer manufacturing is growing very fast in various industries such as biomedical, aircraft, and aerospace industries. There is a need for developing simulation tools for predicting transient temperature fields in additive layer manufacturing of three-dimensional (3D) complex parts in these industries. Transient temperature fields in additive manufacturing are critical due to the fact that transient temperatures directly affect residual stresses, microstructure, fatigue life, 3D distortions, and deformations of produced parts. Considering this industrial need, this article introduces a new approach to 3D transient thermal analysis for additive manufacturing for 3D complex industrial structures with freeform features in powder bed systems using laser heat source. Incorporating the features of phase changes, porous media, and temperature-dependent thermal material properties in COMSOL Multiphysics, the developed technique is able to simulate instantaneous transient temperature fields in additive layer manufacturing of 3D complex and freeform structures. Temperature model validations are performed on titanium alloy with the experimental temperature measurements available in the literature. It is observed that the predicted model simulation results agree well with the experimental measurements.

Journal ArticleDOI
TL;DR: In this article, a wide-area control approach was proposed to improve the transient stability of the power systems while also damping the post-fault inter-area oscillations.
Abstract: This paper presents a wide-area control approach to improve the transient stability of the power systems while also damping the post-fault inter-area oscillations. The proposed approach employs a nonlinear Kalman filter to estimate the inter-area modes using phasor measurement units (PMUs). The wide-area control system then uses the estimated inter-area dynamics through the developed control algorithms to improve the first swing and damping stability of the system. The performance of the proposed approach is evaluated on the simplified Australian test system with different load models including induction motors and the results show significant improvement in the stability of the system by simply adding the wide-area control signals to the available controllers in the system. The application of the proposed wide-area control system is shown to be feasible on realistic systems by improving the system stability and efficiency.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss various transient trajectories for increasing the magnetization state (MS) of variable flux permanent magnet synchronous machines (PMSMs), a class of PMSM where the magnets are demagnetized and remagneticized using the drive inverter during drive cycle operation.
Abstract: This paper discusses various transient trajectories for increasing the magnetization state (MS) of variable flux permanent magnet synchronous machines (PMSMs), a class of PMSM where the magnets are demagnetized and remagnetized using the drive inverter during drive cycle operation. To manipulate MS, a magnetizing current pulse can be used, which may drive a large amount of flux linkage in the machine. As a result, above low-speed operation, a large voltage may be required from the inverter. This paper extends several existing methods for improved voltage properties, and proposes and experimentally evaluates a new method—a straight line stationary frame flux linkage trajectory—for higher speed capability. The presented trajectories, along with existing trajectories, are organized into families and compared regarding their required voltage, high-speed capability, torque ripple, and time duration.

Journal ArticleDOI
TL;DR: “power-neutral” operation is proposed, a new paradigm for transient computing systems, whereby the instantaneous power consumption of the system must match the instantaneous harvested power.
Abstract: Transient computing systems do not have energy storage, and operate directly from energy harvesting. These systems are often faced with the inherent challenge of low-current or transient power supply. In this paper, we propose “power-neutral” operation, a new paradigm for such systems, whereby the instantaneous power consumption of the system must match the instantaneous harvested power. Power neutrality is achieved using a control algorithm for dynamic frequency scaling, modulating system performance gracefully in response to the incoming power. Detailed system model is used to determine design parameters for selecting the system voltage thresholds where the operating frequency will be raised or lowered, or the system will be hibernated. The proposed control algorithm for power-neutral operation is experimentally validated using a microcontroller incorporating voltage threshold-based interrupts for frequency scaling. The microcontroller is powered directly from real energy harvesters; results demonstrate that a power-neutral system sustains operation for 4%–88% longer with up to 21% speedup in application execution.

Journal ArticleDOI
TL;DR: In this paper, a Lumped Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet is presented, which includes non-linear dynamic effects such as the dependence of the magnet's differential self-inductance on the presence of inter-filament and interstrand coupling currents in the conductor.

Journal ArticleDOI
TL;DR: In this paper, the design and implementation of a new control system for reactive power compensation and mechanical torque, voltage regulation and transient stability enhancement for wind turbines equipped with fixed-speed induction generators (IGs) in power systems is presented.

08 Feb 2016
TL;DR: In this article, the characteristics of cell polarization V-I curves are studied for three different dynamic models (Dicks, impedance and electrical equivalent circuit) using MATLAB-SimulinkTM, providing an adequate evaluation of each model under different load conditions.
Abstract: Different Fuel Cell (FC) stacks or system models must be developed relevance to a specified main objective,either an accurate electro-chemical behavior descriptionoroptimization procedure at a system level. In this paper,the characteristics of cell polarization V-I curves arestudied for three different dynamicmodels (Dicks, impedance and electrical equivalent circuit). Thesimulation results, usingMATLAB-SimulinkTM,provideanadequateevaluation of each modelunder different load conditions.Although the different models provide acceptable results and are suitable for many applications particularlyembedded systems, the electrical equivalent circuit model offers accuracy four times better than the Dicks model.The experimental validation of the FC voltage-current characteristic obtained by the different models at steady-state and transient conditions is performed. The agreement between the simulation and the experimental results is adequate.

Journal ArticleDOI
TL;DR: In this article, a three-dimensional thermal weight function (TWF) method was proposed for solving elliptical interface crack problems in bimaterial structures under a transient thermal loading.
Abstract: Different from previous two-dimensional thermal weight function (TWF) method, a three-dimensional (3D) TWF method is proposed for solving elliptical interface crack problems in bimaterial structures under a transient thermal loading. The present 3D TWF method based on the Betti's reciprocal theorem is a powerful tool for dealing with the transient thermal loading due to the stress intensity factors (SIFs) of whole transient process obtained through the static finite element computation. Several representative examples demonstrate that the 3D TWF method can be used to predict the SIFs of elliptical interface crack subjected to transient thermal loading with high accuracy. Moreover, numerical results indicate that the computing efficiency can be enhanced when dealing with transient problems, especially for large amount of time instants.

Journal ArticleDOI
TL;DR: In this paper, different guide-vane closing schemes for reducing the maximum transient pressures, including the water-hammer and pulsating pressures, and runaway speed were investigated, and the principles for improving the closing schemes were theoretically analyzed based on the transient characteristics in the S-shaped region.
Abstract: During the transitional processes of load rejection in a pumped-storage station, the S-shaped characteristics of the pump-turbines can result in relatively large water-hammer and pulsating pressures. These pressures and the high runaway speed during transient processes may directly damage the penstocks and shorten the life of the turbine. In this study, different guide-vane closing schemes for reducing the maximum transient pressures, including the water-hammer and pulsating pressures, and runaway speed were investigated, and the principles for improving the closing schemes were theoretically analyzed based on the transient characteristics in the S-shaped region. First, an analytical expression for the rate of change of relative water head during the transitional processes was deduced based on a simplified mathematical model. It reveals the relationship between the slopes of the trajectory at the pump-turbine operating points (defined as trajectory slopes) and the rigid water-column pressure, which approximates the water-hammer pressure considering compressibility. Then, based on the characteristics of the rigid water-column pressure during the transient process and the effects of guide-vane closure on the trajectory slopes, the selection method for a two-phase guide-vane closing scheme was proposed. The method included the technique for choosing the coordinates of the turning point and the closing speed of the guide vane. Furthermore, the pulsating pressures of pump-turbines were discussed under different working regions and guide-vane openings (GVOs). Considering the characteristics of the pulsating pressures and the runaway speed during the transient processes, the advantage of three-phase valve-closing schemes in controlling the pulsating pressures and the runaway speed was clarified. Finally, a series of model tests were conducted on a pumped-storage station model and the measured data fully validated the correctness of our analyses in this work.

Journal ArticleDOI
TL;DR: In this paper, a dominant-pole substitution (DPS) technique for low-dropout regulator (LDO) is proposed, which involves signal-current feedforward and amplification such that an ultralow-frequency zero is generated to cancel the dominant pole of LDO, while a higher frequency pole substitutes in and becomes the new dominant pole.
Abstract: A dominant-pole substitution (DPS) technique for low-dropout regulator (LDO) is proposed in this paper. The DPS technique involves signal-current feedforward and amplification such that an ultralow-frequency zero is generated to cancel the dominant pole of LDO, while a higher frequency pole substitutes in and becomes the new dominant pole. With DPS, the loop bandwidth of the proposed LDO can be significantly extended, while a standard value and large output capacitor for transient purpose can still be used. The resultant LDO benefits from both the fast response time due to the wide loop bandwidth and the large charge reservoir from the output capacitor to achieve the significant enhancement in the dynamic performances. Implemented with a commercial 0.18-μm CMOS technology, the proposed LDO with DPS is validated to be capable of delivering 100 mA at 1.0-V output from a 1.2-V supply, with current efficiency of 99.86%. Experimental results also show that the error voltage at the output undergoing 100 mA of load transient in 10-ns edge time is about 25 mV. Line transient responses reveal that no more than 20-mV instantaneous changes at the output when the supply voltage swings between 1.2 and 1.8 V in 100 ns. The power-supply rejection ratio at 3 MHz is −47 dB.


Journal ArticleDOI
TL;DR: In this article, the sensitivity analysis of hydraulic transient for two parallel pump-turbine units operating at runaway (unstable S-shaped zone of pump-turbine hill-chart) has been numerically investigated.

Journal ArticleDOI
TL;DR: In this paper, a useful equivalent circuit model was developed to simulate the spontaneous transient balancing currents among parallel strings in a battery system and validated with experimental data to illustrate the accuracy and validity of the model predictions.

Journal ArticleDOI
TL;DR: This model has been found to give an accurate picture of the long term evolution of synchronous machines in the engineering literature for post fault studies and is studied to find evidence that some stable fix points of the swing equation become unstable when the authors add voltage dynamics.
Abstract: Extreme events are a challenge to natural as well as man-made systems. For critical infrastructure like power grids, we need to understand their resilience against large disturbances. Recently, new measures of the resilience of dynamical systems have been developed in the complex system literature. Basin stability and survivability respectively assess the asymptotic and transient behavior of a system when subjected to arbitrary, localized but large perturbations in frequency and phase. To employ these methods that assess power grid resilience, we need to choose a certain model detail of the power grid. For the grid topology we considered the Scandinavian grid and an ensemble of power grids generated with a random growth model. So far the most popular model that has been studied is the classical swing equation model for the frequency response of generators and motors. In this paper we study a more sophisticated model of synchronous machines that also takes voltage dynamics into account, and compare it to the previously studied model. This model has been found to give an accurate picture of the long term evolution of synchronous machines in the engineering literature for post fault studies. We find evidence that some stable fix points of the swing equation become unstable when we add voltage dynamics. If this occurs the asymptotic behavior of the system can be dramatically altered, and basin stability estimates obtained with the swing equation can be dramatically wrong. We also find that the survivability does not change significantly when taking the voltage dynamics into account. Further, the limit cycle type asymptotic behaviour is strongly correlated with transient voltages that violate typical operational voltage bounds. Thus, transient voltage bounds are dominated by transient frequency bounds and play no large role for realistic parameters.

Journal ArticleDOI
TL;DR: This paper develops mathematical models for transient analysis and derives closed-form expressions for evaluating the production rate, consumption rate, work-in-process, and probabilities of machine starvation and blockage, during transients, and develops a computationally efficient algorithm to approximate the transient performance measures with high accuracy.
Abstract: A production system is characterized by both its steady state and transient properties. While extensive research efforts have been spent in the analysis of the steady state of production systems, very few results, especially analytical ones, have been reported regarding their transient behavior. Indeed, transient behavior of production systems has significant practical and theoretical implications. A better understanding of the transient properties of production systems is critical to effective utilization of real-time production data for efficient factory floor operation and management. In the framework of serial production lines with geometric machines and finite buffers, this paper develops mathematical models for transient analysis and derives closed-form expressions for evaluating the production rate, consumption rate, work-in-process, and probabilities of machine starvation and blockage, during transients. In addition, a computationally efficient algorithm based on aggregation is developed to approximate the transient performance measures with high accuracy. Numerical experiments show that the methods developed can be applied to systems with time-varying machine parameters as well.