Amplitude Of Fundamental Component Research Articles

Discrimination Method of Interturn Short-Circuit and Resistive Unbalance Faults for Synchronous Condenser

In this paper, a discrimination method is proposed for the interturn short-circuit and resistive unbalance faults of the synchronous condenser. The mathematical models of the synchronous condenser are established under these two faults. Especially, the zero-sequence voltage components (ZSVC) under two faults are analyzed. Due to the direct connection between the synchronous condenser and the power grid, the fundamental component of ZSVC under the interturn short-circuit fault is not affected by the stator currents, while the resistive unbalance fault is just the opposite. Hence, the amplitude of fundamental component in ZSVC is used to detect the fault occurrence. Then, the change of the fundamental component in ZSVC is observed by changing the excitation current to discriminate the fault type. The effectiveness of the proposed method is verified by the simulation and experimental results.

Dual-Side Asymmetrical Voltage-Cancelation Control for Bidirectional Inductive Power Transfer Systems

Bidirectional inductive power transfer (BIPT) systems for electric vehicles allow power exchange between grid and vehicle. To achieve high transfer efficiency under a wide range of transmission power, this article proposes a dual-side asymmetrical voltage-cancelation (AVC) control technique. With the proposed dual-side AVC control, the adjustment of the fundamental component amplitude of the excitation voltage, the maintenance of a large phase angle between excitation voltages as well as zero-voltage switching (ZVS) of the power switches, and the optimization of the resonant tank power transfer efficiency can be achieved simultaneously. The basic characteristics and the conditions for maximum transfer efficiency of the resonant tank are derived. The control scheme for the overall system including the control of the primary-side and secondary-side full bridges is proposed, which considers both efficiency optimization and ZVS operation of all switches. The ZVS range of the proposed dual-side AVC control technique is presented. Experiments are performed with dual-phase-shift, triple-phase-shift, and the proposed dual-side AVC control technique, which show that the BIPT system with the proposed dual-side AVC control technique achieves a higher efficiency over the others in a wide range of transmission power.

New Dead-Time Compensation Method of Power Inverter using Carrier Based Sinusoidal Pulse-Width Modulation

<p>A new dead-time compensation method of power inverter circuits is suggested and presented in this paper. The proposed method utilizes carrier based sinusoidal pulse width modulation technique to produce driving signals of the inverter power switches with dead-time correction capability. The proposed method able to eliminate dead-time effects such as reducing the waveform distortion of the inverter output current, and increasing the fundamental component amplitude of output current. An analysis of the proposed method is presented. Some computer simulations were carried out to investigate the principle operation, and to test performance of the new method. The developed method was validated through experimental test of H-bridge voltage source inverter circuits. The data obtained from the computer simulation and prototype experiments have confirmed that that the proposed method worked well compensating the dead-time in the voltage source power inverter circuits.</p>

Bearing Fault Analysis in Induction Motor Drives Using Finite Element Method

Diagnosis of faults in induction motor is an indispensable process in industries to improve the reliability of the machine and reduce the financial loss. Among the various faults occurring in induction motors (IM), bearing fault is the predominant one which covers nearly 60% of faults. In this paper, a study of the electromagnetic field of an induction motor with bearing fault fed from both the mains and a three phase voltage source PWM inverter in open loop is carried out using Finite element method (FEM). Electromagnetic field parameters like flux lines distribution, flux density distribution and radial air gapflux density are analyzed. The presence of bearing fault can be detected from the spatial FFT spectrum of radial air gap flux density. From the FFT spectrum, it is seen that the amplitude of fundamental component of radial air gap flux density decreases and those around 100 mm distance increases with the severity of fault.

A Detection Method for Induction Motor Bar Fault Using Sidelobes Leakage Phenomenon of the Sliding Discrete Fourier Transform

The Fourier transform is widely used to diagnose induction motor faults through the monitoring of fault signatures from measured signals such as stator currents. For a good frequency resolution, Fourier transform needs a long signal acquisition time that increases the probability of speed fluctuations which, leads to fault signatures variations. In addition, limited acquisition time and acquired points generate unwanted sidelobes leakage phenomenon, caused by step frequency resolution. In signal processing, the use of window functions allows the avoidance of this phenomenon with the cost of losing a part of signal information. In this paper, the authors propose a new method for the diagnosis of induction motor broken bar fault based on sliding window discrete Fourier transform and the effect of sidelobes of sideband frequencies on the fundamental component amplitude of stator current. The main advantage of the proposed method is that one can detect the amplitude of the fault indicator frequency in vicinity of the fundamental one in shorter time and with good precision even if the motor turns at no-load when compared to used methods, as fast Fourier transform, zoom fast Fourier transform, multiple signal classification, and zoom multiple signal classification. The simulation and experimental results validate the effectiveness of the proposed method.

Detection of Interturn Short-Circuit Fault for PMSM With Simple Fault Indicator

Interturn short-circuit fault is a kind of initial failure of the permanent magnet synchronous motor (PMSM) and serious consequences may be caused if it is left undetected. In this letter, a simple fault indicator is defined as the sum of the absolute values of amplitude differences between the stator currents, where the amplitudes of fundamental components of the stator currents are calculated by the frequency-tracking algorithm. Then, an online interturn short-circuit fault detection method is proposed for the PMSM. The experimental results validate the effectiveness of the proposed method.

Close-Operation Overvoltage of No-Load Transmission Line with Fault Current Limiter

The comprehensive impacts of series resonance type fault current limiter (FCL) on power system need further investigation and verification. With regard to switching on 500kV EHV no-load transmission line, the instantaneous peak value, the free component oscillation frequency, the fundamental component amplitude and free component amplitude of terminal overvoltage waveform are simulated with and without installation of FCL considering different switching times. The relationship curves of free component oscillation period, the fundamental component amplitude and free component amplitude are gotten respectively by simulation results. The law of the influence of different fault current limiting reactance on terminal voltage of switching on no-load line is also summarized. The analysis results show that the installation of FCL is benefit for switching on no-load line.

Space vector PWM for a two-phase VSI

This paper proposes space vector pulse width modulation (SVPWM) technique to control a two-phase full bridge voltage source inverter (VSI) having reduced number of static switches with higher phase voltage output. SVPWM gives higher fundamental component amplitude, provides more efficient use of DC supply voltage and generates less harmonic distortion in the output voltages and currents than other pulse width modulation (PWM) techniques. Between asymmetric and symmetric SVPWM only symmetric one is considered so that the harmonic contents are minimized and two different timing sequences and corresponding switching states are proposed. For the implementation three level switching patterns are determined by using software. For real time application these theoretically determined switching signals for the six power transistors are generated by a digital signal processor (DSP) kit and finally the two-phase output voltages are applied to load. The experimental results are found good and in agreement with the theoretical results. Mathematical analysis along with theoretical and experimental performance of the proposed inverter are presented. Total harmonic distortion (THD) and distortion factor (DF) show that the output voltage quality is good enough to apply in any type of practical two-phase load.

Over-current relay implementation assuring fast and secure operation in transient conditions

In order to reduce hazardous effects of over current caused by faults, faster operation of over-current protections is desirable which means maximum sensitivity of the over-current relays to the current and a minimum reaction time. This high sensitivity may lead to operation of relays in normal transient events, such as transformers energizing and induction motors starting. Therefore, proper methods must be used to prevent mal-trip of the relays, due to these transient currents. This paper presents a new method to discriminate over currents caused by fault from transformer energizing and induction motors starting. In this method, a criterion function is introduced in terms of variation of fundamental component amplitude of current signal over consecutive segments. The criterion function is then used in over-current protection, and faults are precisely discriminated from non-fault switching. The performance of this method is demonstrated by simulation of different faults and switching conditions on the IEEE 13 bus test system using Electromagnetic Transients Program (EMTP) and field measured data.

A property of the nonlinearly geznnerated second-harmonic component of focused ultrasound detected by a concave receiver

The property of the fundamental and second-harmonic components of the acoustic pressure in a beam emitted from a uniformly excited focusing source has been investigated for the cases of the free field and the field with an inserted sample. Calculation of the detection by a concave receiver placed beyond the focal region, which is based on the successive approximation solution for the Khokhlov-Zabolotskaya-Kuznetsov equation, is validated through experiments. The range dependence of the fundamental component amplitude differs from that of the second harmonic, unlike the case of a Gaussian source. The cancellation of the second harmonic components generated in front of, and beyond, the focal region is degraded compared with the case of a Gaussian source. The result of the experimental determination of the nonlinearity parameter B/A for the inserted sample, utilizing the signal received beyond the sample, shows slightly poorer agreement with the literature values, owing to the less sensitive property of the second-harmonic component to the inserted sample.

Detection of nonlinearly propagating focused sound emitted from uniform source using a concave receiver.

The property of the fundamental and second harmonic components of the acoustic pressure in the beam emitted from a uniformly excited focusing source, which is detected by a concave receiver put normal to the acoustic axis beyond the focal region, has been investigated for both the cases of the free field and the field with inserted sample. Calculation based on the successive approximation solution for the Khokhlov-Zabolotskaya-Kuznetsov equation is validated through experiments. It has been clarified that the range dependence of the fundamental component amplitude differs from that of the second harmonic, unlike the case of a Gaussian source, and the cancellation of the second harmonic components generated in front of and beyond the focal region is degraded comparing with the case of Gaussian source. The signal experimentally received beyond the sample corresponds fairly well with the theoretical prediction, taking into account the acoustic properties of the inserted sample. However, the result of experimental determination of the B/A utilizing such responses shows slightly poorer agreement with the literature values, due to the less sensitive property of the second harmonic component to the inserted sample.

Time-Ratio Control of Chopper-Type AC Voltage Regulators

This paper discusses an improved technique and a completed design of a microprocessor-based AC voltage regulator circuit. The proposed regulator is working in the chopping mode and hence presents improvements in its performance characterized by:a) Control range is independent of load phase angle.b) Linear relationship is almost achieved between time ratio and amplitude of fundamental component of load voltage.c) Order of dominant load voltage harmonics can be controlled through changing chopping frequency.The designed controller employs Z80 microprocessor. Flow chart of the program used along with system hardware are provided. Experimental and related theoretical results for controller performance on static loads are presented. Moreover, a comparison with the phase-angle control strategy is presented demonstrating the merits inherited by the proposed scheme.

SOLUTIONS INCORPORATING MAGNETIC HYSTERESIS TO THE SUBHARMONIC PROBLEM IN POWER SYSTEMS

ABSTRACT One possibility of taking care of the subharmonics in high speed protection is to filter the fundamental frequency components from the fault transients and use them for fault detection and discrimination. This is correct only if the phases and amplitudes of fundamental components during and post-subharmonic periods remain the same in transient waveforms. An attempt is therefore made to establish this aspect by a detailed study of a typical electrical network presenting subharmonics. The Dual Input Describing Function is adopted to show the subharmonic boundaries and the influence of system parameters on subharmonic oscillations. Magnetic hysteresis is incorporated in the analysis. A fifth order nonlinearity and one-third subharmonic are assumed. The theory could be easily extended to any order of nonlinearity and to any subharmonic frequency and also to a combination of subharmonics. The analysis gives a set of nonlinear algebraic equations. These equations are solved by Newton's technique using ...

Analysis of intracranial pressure waveform during infusion test

An analysis of intracranial pressure (ICP), based on an examination of the temporary correlation between the changes in amplitude of the pulse wave and the mean ICP level, is presented. The paper contains a discussion of the preliminary results of the method when applied to the analysis of ICP as monitored during infusion tests in a group of 24 children. Infusion of a certain volume of CSF is a good example of an uncompensated volume process, introduced externally into the intracranial space. Results allow an interpretation of the short term correlation coefficient RAP (correlation coefficient between ICP and variations of the amplitude of fundamental component of the pulse wave AMP), as a steady state index. According to this interpretation, the presented analysis enables the observation of a loss of equilibrium during the test. Other phenomena can also be observed, for instance a recovery to equilibrium after the test, nonlinearities of amplitude-pressure relationship, vasomotor reflexes etc.

Impact-pair under periodic excitation

Stability regions of two equispaced impacts/period motion of an impact-pair under prescribed periodic displacement are determined analytically. Theoretical predictions and results from digital simulation are in agreement. The effect of higher frequency components is insignificant when their amplitude is small as compared to the amplitude of fundamental component; however, non-small high frequency components may have stabilizing or destabilizing effects.

The auditory neurophonic: Basic properties

In anesthetized cats an AC signal or neurophonic can he recorded from the auditory nerve and from the scalp when the cochlea is stimulated with low frequency tones. This study examines some of the basic properties of the auditory neurophonics. The auditorynerve signal, termed the auditory nerve neurophonic (ANN), was differentially recorded with a pair of plalinum-iridium ball electrodes placed on either side of the auditory nerve as it exits the internal meatus. The signal recorded from the scalp, termed the frequency following response (FFR), was recorded with silver wire. For purposes of comparison the round window-recorded cochlear microphonic was also examined under identical stimulus conditions. Several measures of the response to acoustic stimulation were taken for each recording configuration. Among these were total response amplitude as a function of stimulus level, spectral component amplitude and phase as a function of stimulus level, fundamental component amplitude as a function of stimulus frequency, response amplitude as a function of time after stimulus onset, response amplitude as a function of forward masker intensity. By all these measures the neurophonic responses are signals that are distinct from the CM and share many of the properties of single units in the auditory nerve. In addition, micro-injections of kainic acid into the cochlear nucleus leave these responses largely unaffected, while tetrodotoxin injections into the cochlea greatly diminish both neurophonic responses, while leaving the CM largely intact. From these results, we conclude that at stimulus levels below 90 dB SPL the ANN is almost entirely neural in origin, while the FFR is certainly largely neural, that is, that both responses are quite distinct from the CM. We also conclude that they represent a spatial summation of neural activity in the auditory nerve, probably arising from the phase-locked response of single units to low frequency stimuli. In addition to demonstrating that the neurophonics are neural responses, we have begun the process of relating their properties to the distributed phase-locked activity in the auditory nerve. auditory nerve, frequency following response, eochlear microphonic