Study on Non-Fundamental Frequency Components in the Output Current of DFIG-Based Wind Turbines During Faults

2018 ◽  
Author(s):  
Wei Jin ◽  
Yuping Lu ◽  
Tao Huang
Keyword(s):  
Fundamental Frequency ◽  
Wind Turbines ◽  
Output Current ◽  
Frequency Components

scholarly journals On the Injection of Sub/Inter-Harmonic Current Components for Active Anti-Islanding Purposes

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2183 ◽  
Author(s):  
Dionisis Voglitsis ◽  
Fotis Valsamas ◽  
Nick Rigogiannis ◽  
Nick Papanikolaou
Keyword(s):  
Fundamental Frequency ◽  
Parallel Operation ◽  
Output Current ◽  
Detection Zone ◽  
Fast Detection ◽  
Pv Systems ◽  
Harmonic Currents ◽  
Distortion Effect ◽  
Specific Frequency ◽  
Detection Response

Active anti-islanding schemes that are based on the injection of harmonic currents, such as the measurement of the impedance at a specific frequency or similar techniques, have been proposed for anti-islanding protection in photovoltaic (PV) systems due to their low impact on inverter active power, their fast detection response in island, and reduced non-detection zone (NDZ). Integer multiples of the fundamental frequency as well as sub/inter-harmonics have both been used for the implementation of those schemes. Although utilization of sub/inter-harmonics present significant advantages, they also present significant limitations. This work investigates those limitations, particularly the ones that are caused by the parallel operation of multiple inverters. In addition, the distortion effect that is caused in the output current of the widely used PV microinverters with pseudo dc-link (PV Pdc-MICs) is discussed and thoroughly analyzed. It is concluded that when the injection is performed asynchronously (without communication among the inverters) sub/inter-harmonics are unsuitable for utilization under the parallel operation of multiple inverters. It is worth noting that a strategy is proposed in the current work that retains the effectiveness of the harmonic injection scheme under the injection of integer multiples of fundamental frequency. On the other hand, the distortion effect that is caused by the sub/inter-harmonics on PV Pdc-MICs output current, has been evaluated as insignificant when harmonics are used for anti-islanding purposes. Finally, the theoretical/mathematical outcomes of this work are supported by simulation and experimental results.

A New Incremental Harmonic Balance Method With Two Time Scales for Quasi-Periodic Motions of an Axially Moving Beam With Internal Resonance Under Single-Tone External Excitation

2019 ◽  
Author(s):  
Jianliang Huang ◽  
Weidong Zhu
Keyword(s):  
Fundamental Frequency ◽  
Time Scales ◽  
Harmonic Balance ◽  
Axially Moving Beam ◽  
Periodic Motions ◽  
Moving Beam ◽  
Frequency Components ◽  
Incremental Harmonic Balance ◽  
Axially Moving ◽  
Ihb Method

Abstract In this work, a new incremental harmonic balance (IHB) method with two time scales, where one is a fundamental frequency, and the other is an interval distance of two adjacent frequencies, is proposed for quasi-periodic motions of an axially moving beam with three-to-one internal resonance under singletone external excitation. It is found that the interval frequency of every two adjacent frequencies, located around the fundamental frequency or one of its integer multiples, is fixed due to nonlinear coupling among resonant vibration modes. Consequently, only two time scales are used in the IHB method to obtain all incommensurable frequencies of quasi-periodic motions of the axially moving beam. The present IHB method can accurately trace from periodic responses of the beam to its quasi-periodic motions. For periodic responses of the axially moving beam, the single fundamental frequency is used in the IHB method to obtain solutions. For quasi-periodic motions of the beam, the present IHB method with two time scales is used, along with an amplitude increment approach that includes a large number of harmonics, to determine all the frequency components. All the frequency components and their corresponding amplitudes, obtained from the present IHB method, are in excellent agreement with those from numerical integration using the fourth-order Runge-Kutta method.

Research on the Whole Condition Loaded Noise Measurement Circuit of Power Capacitor

2014 ◽  
Vol 490-491 ◽  
pp. 1647-1651
Author(s):  
Guo Xing Huang ◽  
Zhi Yuan Li ◽  
Yin Huang ◽  
You Meng Lu
Keyword(s):  
Fundamental Frequency ◽  
Harmonic Signal ◽  
Noise Spectrum ◽  
Noise Measurement ◽  
Harmonic Frequency ◽  
Hvdc Transmission ◽  
High Voltage Direct Current ◽  
Frequency Components ◽  
The One ◽  
Parallel Resonance

Power capacitor is one of the key equipments of the high-voltage direct current (HVDC) transmission system. It is also the main noise source difficult to control. Presently in the world, there are none explicit requirement and regulation on the evaluation and measurement of the noise generated by the power capacitor, which has seriously restricted the development of the further research on the noise control in power capacitor. So the research on the noise measurement method and technology has extremely important significance in scientifically evaluating the noise of power capacitor. Power capacitor in HVDC Converter Station under practical conditions has apparent fundamental frequency and rich harmonic frequency components. In order to simulate this condition, a whole condition loaded bridge circuit of noise measurement on power capacitor has been designed and studied. Two arms of the bridge are used to load fundamental frequency and a parallel resonance compensation inductance is used to reduce the fundamental current, while the other two arms are used to load harmonic frequency. The harmonic frequency load power supply composed of harmonic signal generator and power amplifier which can simultaneously load any combination of harmonics under 48th to simulate the various actual working conditions. The tests indicated that the noise spectrum measured under the designed circuit completely accorded with the one in HVDC Converter Station.

An analytic method for measuring accurate fundamental frequency components

2002 ◽  
Vol 17 (2) ◽  
pp. 405-411 ◽  
Author(s):  
Soon-Ryul Nam ◽  
Sang-Hee Kang ◽  
Jong-Keun Park
Keyword(s):  
Fundamental Frequency ◽  
Analytic Method ◽  
Frequency Components

A New Incremental Harmonic Balance Method With Two Time Scales for Quasi-Periodic Motions of an Axially Moving Beam With Internal Resonance Under Single-Tone External Excitation

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
J. L. Huang ◽  
W. D. Zhu
Keyword(s):  
Fundamental Frequency ◽  
Time Scales ◽  
Harmonic Balance ◽  
Axially Moving Beam ◽  
Periodic Motions ◽  
Moving Beam ◽  
Frequency Components ◽  
Incremental Harmonic Balance ◽  
Axially Moving ◽  
Ihb Method

Quasi-periodic motion is an oscillation of a dynamic system characterized by m frequencies that are incommensurable with one another. In this work, a new incremental harmonic balance (IHB) method with only two time scales, where one is one of the m frequencies, referred to as a fundamental frequency, and the other is an interval distance of two adjacent frequencies, is proposed for quasi-periodic motions of an axially moving beam with three-to-one internal resonance under single-tone external excitation. It is found that the interval frequency of every two adjacent frequencies, located around the fundamental frequency or one of its integer multiples, is fixed due to nonlinear coupling among resonant vibration modes. Consequently, only two time scales are used in the IHB method to obtain all incommensurable frequencies of quasi-periodic motions of the axially moving beam. The present IHB method can accurately trace from periodic responses of the beam to its quasi-periodic motions. For periodic responses of the axially moving beam, the single fundamental frequency is used in the IHB method to obtain solutions. For quasi-periodic motions of the beam, the present IHB method with two time scales is used, along with an amplitude increment approach that includes a large number of harmonics, to determine all the frequency components. All the frequency components and their corresponding amplitudes, obtained from the present IHB method, are in excellent agreement with those from numerical integration using the fourth-order Runge–Kutta method.

Special Cases of Input Speed Doubling Linkage Mechanisms and Their Dynamics Advantage

2004 ◽  
Author(s):  
J. Rastegar ◽  
J. Zhang
Keyword(s):  
Fundamental Frequency ◽  
Linkage Mechanism ◽  
Practical Applications ◽  
Special Cases ◽  
Lower Amplitude ◽  
Full Rotation ◽  
Rocking Motion ◽  
Frequency Components ◽  
Special Case ◽  
Input Torque

In a recent study, Rastegar, et al. (2003), presented a special class of planar and spatial linkage mechanisms in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. In a special case of such mechanisms, for periodic motions of the input link, the output motion is periodic with a doubled fundamental frequency. The above class of linkage mechanisms were referred to as “speed-doubling” linkage mechanisms. Such mechanisms can be cascaded to further double the fundamental frequency (rocking motion) of the output motion. They can also be cascaded with other linkage mechanisms to obtain crank-rocker or crank-crank type of mechanisms. The conditions for the existence of “speed-doubling” linkage mechanisms were also provided. In this paper, a study of the dynamics of a “speed-doubling” linkage mechanism is presented. It is shown that such mechanisms have dynamic advantage over regular mechanisms designed to achieve similar output motions. The main advantage of such mechanisms is shown to be their lower peak input torque requirement, and that the required torque generally has lower amplitude high-frequency components. The speed-doubling mechanisms have practical applications, particularly when higher output speeds are desired, since higher output motions can be achieved with lower input speeds and smaller motors.

The Dynamics of Leakage in Bent Axis Units Without Timing Gear

2016 ◽  
Author(s):  
Bernhard Manhartsgruber
Keyword(s):  
Fundamental Frequency ◽  
High Efficiency ◽  
Low Frequency ◽  
Speed Range ◽  
Frequency Components ◽  
Flow Pulsations ◽  
Cylinder Barrel ◽  
Large Speed

Bent axis hydraulic pumps and motors are extremely popular due to their high efficiency and large speed range. A number of different concepts exist with respect to kinematic restraints on the cylinder barrel motion. Some manufacturers rely upon a timing gear for precise synchronization of the shaft and barrel speeds while other companies have successfully introduced bent axis units without such a mechanism. The paper analyses the dynamics of bent axis machines with tapered pistons driving the cylinder barrel. A rotation of the pistons inside the corresponding bores is proposed to result in changing cylinder chamber to case drain leakages. The reported phenomenon is shown to have a significant effect on the low frequency part of pressure and flow pulsations. In this way, frequency components far below the fundamental frequency associated with the shaft revolution are generated.

scholarly journals Low frequencies in the display vocalization of the Western Capercaillie (Tetrao urogallus)

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9189
Author(s):  
Vlastimil Hart ◽  
Richard Policht ◽  
Vojtěch Jandák ◽  
Marek Brothánek ◽  
Hynek Burda
Keyword(s):  
Fundamental Frequency ◽  
Bird Species ◽  
Low Frequency ◽  
Tetrao Urogallus ◽  
Vocal Expression ◽  
Low Frequencies ◽  
Discrimination Analysis ◽  
Frequency Components ◽  
Specific Individual ◽  
Casuarius Casuarius

Only a few bird species are known to produce low-frequency vocalizations. We analyzed the display vocalizations of Western Capercaillie males kept in breeding centers and identified harmonically structured signals with a fundamental frequency of 28.7 ± 1.2 Hz (25.6–31.6 Hz). These low-frequency components temporally overlap with the Whetting phase (96% of its duration) and they significantly contribute to the distinct vocal expression between individuals. The resulting model of discrimination analysis classified 67.6% vocalizations (63%, cross-validated result) correctly to the specific individual in comparison to the probability by chance of 12.5%. We discuss a possible function of low-frequency components that remains unclear. The occurrence of such low frequencies is surprising as this grouse is substantially smaller than cassowaries (Southern cassowary Casuarius casuarius and Dwarf cassowary Casuarius bennetti) , the species that produces similarly low frequencies. Because these low frequency components temporarily overlap with the Whetting phase, they are hardly audible from a distance larger than several meters.

scholarly journals A Numerical Study for Flow Excitation and Performance of Rampressor Inlet considering Rotor Motion

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Weijia Kang ◽  
Zhansheng Liu ◽  
Jiangbo Lu ◽  
Yu Wang ◽  
Yanyang Dong
Keyword(s):  
Power Systems ◽  
Fundamental Frequency ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Frequency Component ◽  
Inlet Flow ◽  
Compressor Rotor ◽  
Frequency Components ◽  
Subsonic Diffuser ◽  
And Performance

A unique supersonic compressor rotor with high pressure ratio, termed the Rampressor, is presented by Ramgen Power Systems, Inc. (RPS). In order to obtain the excitation characteristic and performance of Rampressor inlet flow field under external excitation, compression inlet flow of Rampressor is studied with considering Rampressor rotor whirling. Flow excitation characteristics and performance of Rampressor inlet are analyzed under different frequency and amplitude of Rampressor rotor whirling. The results indicate that the rotor whirling has a significant effect for flow excitation characteristics and performance of Rampressor inlet. The effect of rotor whirling on the different inlet location excitation has a definite phase difference. Inlet excitation becomes more complex along with the inlet flow path. More frequency components appear in the excitation spectrum of Rampressor inlet with considering Rampressor rotor whirling. The main frequency component is the fundamental frequency, which is caused by the rotor whirling. Besides the fundamental frequency, the double frequency components are generated due to the coupling between inlet compression flow of Rampressor rotor and rotor whirling, especially in the subsonic diffuser of Rampressor rotor inlet. With the increment of rotor whirling frequency and whirling amplitude, the complexity of Rampressor inlet excitation increases, and the stability of Rampressor inlet performance deteriorates.

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