33,416 research outputs found
Improved p-q Harmonic Detection Method for Hybrid Active Power Filter
The accuratedetermination of the load harmonic current is one of the important factors, it decides to effect of harmonic filtering and reactive power compensation for Hybrid Active Power Filter. The p-q harmonic detection method has been widely used in determining the harmonic currents of Hybrid Active Power Filter. However, when using this method, the dynamic response of Hybrid Active Power Filter in the transient period will have a large transient time and overshoot whenever the load changes abruptly. Therefore, in this paper an improved p-q harmonic current detection method based on fuzzy logic is proposed, which aims to reduce the overshoot and transient time in transient duration of Hybrid Active Power Filter. In order to compare the dynamic response of conventional and improved p-q harmonic detection methods, simulation results have demonstrated that: the proposed method has a shorter response time, the magnitude of the supply current in the transient time is smaller and the overshoot of the fundamental active and reactive power components is very small. This has a practical significance that contributes to the stability of the Hybrid Active Power Filter syste
New trends in active filters for improving power quality
Since their basic compensation principles were proposed around 1970, active filters have been studied by many researchers and engineers aiming to put them into practical applications. Shunt active filters for harmonic compensation with or without reactive power compensation, flicker compensation or voltage regulation have been put on a commercial base in Japan, and their rating or capacity has ranged from 50 kVA to 60 MVA at present. In near future, the term of active filters will cover a much wider sense than that of active filters in the 1970s did. The function of active filters will be expanded from voltage flicker compensation or voltage regulation into power quality improvement for power distribution systems as the capacity of active filters becomes larger. This paper describes present states of the active filters based on state-of-the-art power electronics technology, and their future prospects toward the 21st century, including the personal view and expectation of the author</p
Frequency and fundamental signal measurement algorithms for distributed control and protection applications
Increasing penetration of distributed generation within electricity networks leads to the requirement for cheap, integrated, protection and control systems. To minimise cost, algorithms for the measurement of AC voltage and current waveforms can be implemented on a single microcontroller, which also carries out other protection and control tasks, including communication and data logging. This limits the frame rate of the major algorithms, although analogue to digital converters (ADCs) can be oversampled using peripheral control processors on suitable microcontrollers. Measurement algorithms also have to be tolerant of poor power quality, which may arise within grid-connected or islanded (e.g. emergency, battlefield or marine) power system scenarios. This study presents a 'Clarke-FLL hybrid' architecture, which combines a three-phase Clarke transformation measurement with a frequency-locked loop (FLL). This hybrid contains suitable algorithms for the measurement of frequency, amplitude and phase within dynamic three-phase AC power systems. The Clarke-FLL hybrid is shown to be robust and accurate, with harmonic content up to and above 28% total harmonic distortion (THD), and with the major algorithms executing at only 500 samples per second. This is achieved by careful optimisation and cascaded use of exact-time averaging techniques, which prove to be useful at all stages of the measurements: from DC bias removal through low-sample-rate Fourier analysis to sub-harmonic ripple removal. Platform-independent algorithms for three-phase nodal power flow analysis are benchmarked on three processors, including the Infineon TC1796 microcontroller, on which only 10% of the 2000 mus frame time is required, leaving the remainder free for other algorithms
DSOGI-PLL based power control method to mitigate control errors under disturbances of grid connected hybrid renewable power systems
The control of power converter devices is
one of the main research lines in interfaced renewable
energy sources, such as solar cells and wind turbines.
Therefore, suitable control algorithms should be
designed in order to regulate power or current properly
and attain a good power quality for some disturbances,
such as voltage sag/swell, voltage unbalances and fluctuations,
long interruptions, and harmonics. Various
synchronisation techniques based control strategies
are implemented for the hybrid power system applications
under unbalanced conditions in literature studies.
In this paper, synchronisation algorithms based
Proportional-Resonant (PR) power/current controller
is applied to the hybrid power system (solar cell + wind
turbine + grid), and Dual Second Order Generalized
Integrator-Phase Locked Loop (DSOGI-PLL) based PR
controller in stationary reference frame provides a solution
to overcome these problems. The influence of
various cases, such as unbalance, and harmonic conditions,
is examined, analysed and compared to the PR
controllers based on DSOGI-PLL and SRF-PLL. The
results verify the effectiveness and correctness of the
proposed DSOGI-PLL based power control method
Basics of RF electronics
RF electronics deals with the generation, acquisition and manipulation of
high-frequency signals. In particle accelerators signals of this kind are
abundant, especially in the RF and beam diagnostics systems. In modern machines
the complexity of the electronics assemblies dedicated to RF manipulation, beam
diagnostics, and feedbacks is continuously increasing, following the demands
for improvement of accelerator performance. However, these systems, and in
particular their front-ends and back-ends, still rely on well-established basic
hardware components and techniques, while down-converted and acquired signals
are digitally processed exploiting the rapidly growing computational capability
offered by the available technology. This lecture reviews the operational
principles of the basic building blocks used for the treatment of
high-frequency signals. Devices such as mixers, phase and amplitude detectors,
modulators, filters, switches, directional couplers, oscillators, amplifiers,
attenuators, and others are described in terms of equivalent circuits,
scattering matrices, transfer functions; typical performance of commercially
available models is presented. Owing to the breadth of the subject, this review
is necessarily synthetic and non-exhaustive. Readers interested in the
architecture of complete systems making use of the described components and
devoted to generation and manipulation of the signals driving RF power plants
and cavities may refer to the CAS lectures on Low-Level RF.Comment: 36 pages, contribution to the CAS - CERN Accelerator School:
Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar
Unbalanced load flow with hybrid wavelet transform and support vector machine based Error-Correcting Output Codes for power quality disturbances classification including wind energy
Purpose. The most common methods to designa multiclass classification consist to determine a set of binary classifiers and to combine them. In this paper support vector machine with Error-Correcting Output Codes (ECOC-SVM) classifier is proposed to classify and characterize the power qualitydisturbances such as harmonic distortion,voltage sag, and voltage swell include wind farms generator in power transmission systems. Firstly three phases unbalanced load flow analysis is executed to calculate difference electric network characteristics, levels of voltage, active and reactive power. After, discrete wavelet transform is combined with the probabilistic ECOC-SVM model to construct the classifier. Finally, the ECOC-SVM classifies and identifies the disturbance type according tothe energy deviation of the discrete wavelet transform. The proposedmethod gives satisfactory accuracy with 99.2% compared with well known methods and shows that each power quality disturbances has specific deviations from the pure sinusoidal waveform,this is good at recognizing and specifies the type of disturbance generated from the wind
power generator.Наиболее распространенные методы построения мультиклассовой классификации заключаются в определении набора двоичных классификаторов и их объединении. В данной статье предложена машина опорных векторов с классификатором выходных кодов исправления ошибок(ECOC-SVM) с целью классифицировать и характеризовать такие нарушения качества электроэнергии, как гармонические искажения, падение напряжения и скачок напряжения, включая генератор ветровых электростанций в системах передачи электроэнергии. Сначала выполняется анализ потока несимметричной нагрузки трех фаз для расчета разностных характеристик электрической сети, уровней напряжения, активной и реактивной мощности. После этого дискретное вейвлет-преобразование объединяется с вероятностной моделью ECOC-SVM для построения классификатора. Наконец, ECOC-SVM классифицирует и идентифицирует тип возмущения в соответствии с отклонением энергии дискретного вейвлет-преобразования. Предложенный метод дает удовлетворительную точность 99,2% по сравнению с хорошо известными методами и показывает, что каждое нарушение качества электроэнергии имеет определенные отклонения от чисто синусоидальной формы волны, что способствует распознаванию и определению типа возмущения, генерируемого ветровым генератором
Bio-Inspired Filter Banks for SSVEP-based Brain-Computer Interfaces
Brain-computer interfaces (BCI) have the potential to play a vital role in
future healthcare technologies by providing an alternative way of communication
and control. More specifically, steady-state visual evoked potential (SSVEP)
based BCIs have the advantage of higher accuracy and higher information
transfer rate (ITR). In order to fully exploit the capabilities of such
devices, it is necessary to understand the features of SSVEP and design the
system considering its biological characteristics. This paper introduces
bio-inspired filter banks (BIFB) for a novel SSVEP frequency detection method.
It is known that SSVEP response to a flickering visual stimulus is frequency
selective and gets weaker as the frequency of the stimuli increases. In the
proposed approach, the gain and bandwidth of the filters are designed and tuned
based on these characteristics while also incorporating harmonic SSVEP
responses. This method not only improves the accuracy but also increases the
available number of commands by allowing the use of stimuli frequencies elicit
weak SSVEP responses. The BIFB method achieved reliable performance when tested
on datasets available online and compared with two well-known SSVEP frequency
detection methods, power spectral density analysis (PSDA) and canonical
correlation analysis (CCA). The results show the potential of bio-inspired
design which will be extended to include further SSVEP characteristic (e.g.
time-domain waveform) for future SSVEP based BCIs.Comment: 2016 IEEE International Conference on Biomedical and Health
Informatics (BHI
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