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To reduce the active power filter (APF) system switching loss, the usual method is to apply different soft-switching techniques. However, this would increase the system initial cost. In this study, a switching loss and switching noise reduction control strategy for APF under reactive power and current harmonics compensation is proposed, which can be applied to the existing APF systems in worldwide,...
This study presents a D–Q current control method with modified phase lock loop to generate the required reference current for shunt hybrid active filter (SHAPF) to improve the power quality. The performance of the proposed controller has been evaluated in terms of harmonic current mitigation and reactive power compensation under different grid conditions. Here, the passive elements of SHAPF have been...
In the commercial sector single-phase, non-linear loads are predominant and their numbers are on the increase. The two-pulse diode bridge rectifier is the most popular single-phase topology deployed for ac-dc conversion of electrical energy; however, when feeding an inductive load, its line current has a total harmonic distortion of around 28%, that is a gross violation of contemporary power quality...
This work presents a relatively new method known as empirical mode decomposition (EMD) for power quality disturbances. In a comprehensive and wider range of approaches and engineering activities, there is a increasing concern for power system disturbances monitoring techniques. The need of increasing performances in terms of accuracy and computation speed is permanently demanding new efficient processing...
The number of doubly fed induction generators (DFIGs) has been grown in recent years because of its merits. They play an important part of the total amount of wind generation. On the other hand due to proliferation of utilizing non-linear loads in power system, power quality problems like harmonics, voltage sag/swell, etc outbreak. These problems have destructive effect of performance of DFIG. To...
PLL principles system and its applications in harmonic analysis are firstly discussed and then integrated presenting methods to increase the PLL-based instrumentation efficiency. A comparison between the performance of systems before and after the application of these methods are shown to validate the efficiency o f the proposed methods.
Power quality has become an important factor in power systems, for consumer and household appliances with proliferation of various electric/ electronic equipment and computer systems. The main causes of a poor power quality are harmonic currents, poor power factor, supply voltage variations, etc. In recent years the demand for the quality of electric power has been increased rapidly. Power quality...
Wind power generation systems influence power quality in a very specific manner creating the requirements for detailed and correct analysis of disturbances caused by wind generators. Wind power system cause sub- and interharmonic disturbances within the spectrum of voltages and currents. The paper shows alternative method of spectrum estimation in power systems, tested on the system with the doubly...
This paper presents a new method for automatic classification of power quality events, developed based on S-transform. This transform provides high resolution time-frequency representations used to calculate power quality indices. Supplementary information about detected events (the magnitude, duration and frequency spectrum of the identified disturbances) are extracted in order to characterize the...
The principle of the dynamic voltage restorer (DVR) to the voltage sag problem with phase angle jump is analyzed in this paper. Based on the fundamental component of steady-state equivalent circuit, the phase diagram with voltage fluctuations and phase angle jump is shown. According to instantaneous reactive power theory and the low-pass filter theory, the initial phase of the source fundamental phase...
Modern lightning system are energetically efficient, but highly nonlinear, drawing non-sinusoidal currents and deteriorating power quality. The best way to reduce harmonics is to install filters. In practice, filters are installed without exact and precise design for every installation site. In some cases the filtration is not optimal, costs do not justify the effect. The authors propose an efficient...
One of the main aspects of power quality is harmonic related problems in power systems. A proper learning of harmonics is essential for power engineers to deal with these problems. This paper reviews the efforts made in teaching power system harmonics in undergraduate and graduate levels. Hardware and software tools have been developed in order to improve the teaching/learning process. General aspects...
Most of the disturbance in the power system is nonlinear and no-stationary. Hilbert-Huang transform (HHT) is an efficient time-frequency analysis method which can detect different kinds of power quality disturbance. HHT consists of empirical-mode decomposition (EMD) and Hilbert transform (HT). EMD can self-adjust according to the characteristics of the signal itself, and decompose the signal into...
This paper addresses a new multi-carrier modulation technique called wave shift multi-carrier modulation (WSHM), which used to control the cascade multilevel converter (CMC). The proposed switching technique generates lower voltage total harmonic distortion (THD) in comparison with conventional multi-carrier based pulse width modulation (PWM) schemes, phase-shift (PSHM) and level-shift (LSHM) modulations...
The 6-pulse controlled rectifier circuit is very well known. For proper operation of the 6-pulse rectifier, it is necessary to synchronise the firing signals with the mains voltage, else the operation of the rectifier is affected. A firing angle controller, without using any phase lock loop (PLL), is described here. This scheme employs the dq-reference frame to estimate the magnitude and phase angle...
The increase use of renewable dc or battery as a source has further emphasized the importance in efficient design of inverter. This paper discusses a study to determine optimum operating parameters of a commonly used pwm unipolar inverter. Variations on the input voltage level and switching frequency will be investigated to see their impacts on the operation of the inverter as well as harmonics produced...
This paper deals with the power flow analysis and control strategy research of unified power quality conditioner (UPQC). A UPQC is a combination of shunt and series active power filter (APF), sharing a common dc link. It can compensate almost all power quality problems such as voltage harmonics, voltage unbalance, voltage flickers, voltage sags, voltage swells, current harmonics, current unbalance,...
In recent years, with the increase of nonlinear loads drawing Nonsinusoidal currents, power quality distortion has become a serious problem in electrical power systems. Distortions in voltage and current wave-shapes can upset end-use equipment and cause other problems. Harmonics are a particularly common type of distortion that repeats every cycle. Poor power quality may cause many problems, such...
Nowadays power quality in power network requests using from existing equipments as high-performance and low cost such as improvement of compensator equipment and ways of efficiency increasing can be reduced destroyer effect on network. Active power filters is more importance and finance in network and industrial. It has depended detector algorithm and switching technique. This paper presents a novel...
Power quality is the set of regulations of electrical properties that allows electrical systems to function without significant loss of performance or aging. The term is used to describe electric power that drives an electrical load and the load's ability to operate properly with that electric power. Without the proper power, an electrical device (or load) may malfunction, fail prematurely or not...
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