ABSTRACT: Three-Phase four-wire distribution systems are widely used for distributing power to many residential and commercial buildings. The increased use of non-linear and unbalanced loads in these systems may result in excessive neutral currents. This may damage the neutral conductor and distribution transformer while affecting the safety of the consumers and also causes several other power quality problems in the system. The proposed strategy employs a new threephaseelectric spring circuit for reducing neutralcurrent in the system. MATLAB/SIMULINK platform is used for simulation. The application of the proposed method has been investigated for different load conditions and the results are presented.
Abstract— Transformer is the most important equipment of the electrical power system. At the time of transformer energization high current is drawn by the transformer known as the inrush current. This current is nearly ten times more than the full load current of transformer. It produces mechanical stress on transformer and also affects the windings and bushings of the transformer. The large switching transient current affects malfunction of protection system of power system and the different equipments connected to system. So the inrush current should be minimized. There are different methods used to minimize the inrush current such as volt second balance, series compensator, point on wave switching method etc. This paper focuses on point on wave switching method. It also explains the results for inrush current of threephase transformer with and without point on wave switching method. A test is driven on 450 kVA, 500kV/230kV grounded Y/D transformer in MATLAB/SIMLINK environment. It also focuses on power quality issues associated with transformer at no load condition.
line conditioners. The term "power conditioning" used in this book has much broader meaning than the term harmonic filtering." In other words, the power conditioning is not confined to harmonic filtering, but contains harmonic damping, harmonic isolation, harmonic termination, reactive-power control for power factor correction, power flow control, and voltage regulation, load balancing, voltage-flicker Suction, and/or their combinations. Active power line conditioners are based on leading-edge power electronics technology that includes power conversion circuits, power semiconductor devices, analog/digital signal processing, voltage/current sensors, and control theory. Concepts and evolution of electric power theory are briefly described below. Then, the need for a consistent set of power definitions is emphasized to deal with electric systems under non-sinusoidal conditions. Problems with harmonic pollution in alternating current systems (ac systems) are classified, including a list of the principal harmonic-producing loads. Basic principles of harmonic compensation are introduced. Finally, this chapter describes the fundaments of power flow control. All these topics are the subjects of scope, and will be discussed deeply in the following chapters of the book. The instantaneous power theory, or ―the p-q theory,‖ makes clear the physical meaning of what instantaneous real and imaginary power is in a three-phase circuit. Moreover, it provides insight into how energy flows from a source to a load, or circulates between phases, in a three- phase circuit. This theory can be used in the design and understanding of FACTS (Flexible AC Transmission System) compensators. The book introduces many concepts in the field of active filtering that are unique to this edition. It provides a study tool for final year undergraduate students, graduate students and engineers dealing i-th harmonic pollution problems, reactive power compensation or power quality in general. 2 EXISTING SYSTEM
Nowadays, poor in power quality in an electrical delivery system is becoming an increasingly challenging because with rapidly growing in used of electrical equipment, power electronic, micro-electronics in modern life, the systems are increasingly incompatible with power environment. Mostly, power system or power that supplied from generator comes as an alternating current, while electrical appliances that being produced nowadays comes in as a direct current.
with energy greater than the band-gap energy of the semiconductor creates some electron-hole pairs proportional to the incident irradiation. To find the model of the photovoltaic generator, we must start by identifying the electrical equivalent circuit to that source. Many mathematical models have been developed to represent their highly nonlinear characteristics resulting from that of semiconductor junctions that are the major constituents of PV modules. There are several models of photovoltaic generators which have a certain number of parameters involved in the calculation of voltage and current output. In this study, we will present the model of single diodes (Fig.2) taking into account the internal shunt and series resistances of the PV cell.
Transformer is an important, essential and costlier element in power system. So, the protection of transformer have the same importance. Protection of ThreePhase Electrical Power Transformer, a digital differential protection is applied in which terminal currents are used. In transformers, abnormal conditions like faults are divided into two categories:-1) Internal 2) External. The phenomenon of internal fault which is originating a profound effect internally on lifetime of an Electrical transformer. During the external faults, short circuit will forces become very much threatening for hidden defects and aged insulation and often causes inter turn shorting. The older aging of insulation materials due to its temperature, specifically at points of a local overheating and is accelerated in the occurring of oxygen and moisture. The Hidden defect is also responsible for insulation physical strength. Usually Internal fault occurs at the high level voltage side in signal phase, and is initially number of turns are small.
The project is one such attempt to identify the level and type of the harmonic distortion in neutral voltage and neutralcurrent waveform caused by certain typical loads which are both non-linear and sensitive to power quality. The paper also reflects the effect of varying power supply on neutral conductor, analysis of neutralcurrent and neutral voltage and their distortion level due to various non-linear loads. Each and every data are analyzed thoroughly in this project. Several conclusions are given which will necessary for designing and installation of the exact mitigating device. It has done by doing a survey in the National Institute of Technology, Agartala to analyze the collected data and give the necessary information based on the analysis. Random sampling at different places of NITA has been carried out to stress the severity of the problem and out of it Electrical Machine laboratory has been taken the place of study for its criticalities.
Abstract— Secondary distribution system is generally ThreePhase Four Wire system which is directly connected to consumers. Due to the unbalanced configuration of these networks, a net current flowing through the neutral conductor. The presence of increasing number of non linear loads also causes significant neutralcurrent in the system. The nonlinear loads draw harmonic and reactive components of current from ac mains. The excess neutralcurrent and harmonics are the serious issues as they deteriorate the overall performance of distribution systems. The proposed strategy employs a new threephaseElectric Spring circuit for reducing neutralcurrent and a Hysteresis Current Controller for eliminating harmonics from the system. MATLAB/SIMULINK software platform is used for simulation. The application of the proposed method has been investigated for different load conditions and the results are presented.
The theory above is for power systems of direct current, whereas the electric power system of alternating current, the power can be divided into three types, namely: the real power that the electric power used load or electrical equipment to do the work, this power is the product of voltage, current and power factor (cos ¢), apparent power is the product of voltage and current, while the reactive power is the power that is used to generate mechanical power and heat, this power is the product of voltage, current and power factor ( sin ¢). Phasa angle ¢ greatly influenced by the type of load is attached, if the load is resistive then the current will same phase with voltage (¢ = 0), if the load is inductive phase currents will be left behind (lagging) of the phase voltage of 90° (¢ = 90°), while if the load is capacitive currentphase will go ahead (leading) of the phase voltage of 90° (¢ = 90°). However, generally load is a combination of all three types of load, so that the current and voltage have a phase angle difference of ¢, so the power factor is cos ¢.
M. Hadj Kacem was born in Sfax (Tunisia) in 1975. He received his Master’s diploma in Electric Engineering from the National School of Engeneers of Sfax-Tunisia in 2007. He is currently a doctorant on the Laboratory of Electronic and Information Technology (LETI-Sfax) in the National School of Engeneers of Sfax-Tunisia. His current research interests include field of electrical machines and power system design, identification, and optimisation. He is co-author of a paper in an international journal.
Today’s world power industry faces enormous challenges from both environment and economy, the international arena are reshaping the power industry to make it to play a more important role in renewable energy industry, thus to deal with global warming and energy depletion. This was reason for distributed generators (DG) to have significant opportunity in the evolving power system network. Both consumers and power utilities can benefit from the widespread deployment of DG systems which offer secure and diversified energy options, increase generation and transmission efficiency, reduce greenhouse gas emissions, improve power quality and system stability, cut energy costs and capital expenditures, and alleviate the bottleneck caused by distribution lines.
BER floor induced by the laser phase noise due to the fast phase changing occurring in the long effective symbol average-span. By contrast, a larger step size will degrade the NLMS phase estimator on the sensitivity of optical signal-to-noise ratio (OSNR), but influence the BER floor induced by the phase fluctuation little. The performance of the one-tap NLMS-CPE using different step size is shown in Fig. 2, where both of the TX and LO lasers linewidths are 5 MHz, and the fiber length is 2000 km. We can see that the one-tap NLMS-CPE shows the best performance when using the optimum step size (μ=0.25), and the BER floor in NLMS-CPE is deteriorated obviously when the smaller step size (μ=0.025) is used. Meanwhile, we find that only the OSNR sensitivity is degraded while the BER floor has no significant variation, when the larger step size (μ=1) is employed in the one-tap NLMS-CPE. Note that the OSNR value is all defined in 0.1 nm and the penalty between the back-to-back result and the theoretical limit (at BER=10 -3 ) is around
ABSTRACT: The main aim of this paper is to compensate current harmonics in PV-APF systemusing Fuzzy Logic Controller. A 3-Ф, 3-wire system is proposed in this paper which consists of PV system, a dc/dc converter which is controlled by MPPT, threephase VSC to act as APF and Non-Linear Load. The main theme of this INC MPPT is to efficiency from the PV system. For reliable performance of active power filter and better harmonic compensation this paper proposes a concept of instantaneous power theory. Also, a comparison analysis is performed for improving THD by PI/Fuzzy controllers. This system is experimentally verified and tested using Simulink.
Filters are of active and passive types. Passive filters are made up of Resistor, Inductor and Capacitor elements. Active Power Filters (APF) are made up of power electronic devices. Since passive filters are simpler and cheaper when compared to active filters, passive filters were considered for harmonic mitigation. Single tuned filter is the most commonly used passive filter. It is very cheap and easy to design. It creates a low impedance path for the corresponding designed order of harmonics and mitigates it. Since passive filters are called "Fixed Frequency Filter", it doesn't respond well to the nonlinear loads. Hence the "Variable Frequency Filter" named active power filter comes into picture. Hybrid power filters are more attractive in harmonic filtering than the pure filters from both viability and economical.
Current and voltage harmonics in power distribution system are generated by non-linear loads such as UPS, inverters, adjustable speed drives and other power electronic equipment which causes power quality issues such as over neutralcurrent, reactive power problem, unbalanced current and low efficiency. In four wire distribution system, due to delta connected primary, the triplen harmonic currents (3rd, 9th, and 15th) can only circulate in primary delta winding of transformer causing overheating. Excessive heating can reduce the bearing lubrication which collapse the bearing. Power cables carrying harmonic loads has a harmful effect on televisions, telephones, control systems and other equipment. The range 540 Hz to 1200 Hz (9th harmonic to 20th harmonic at 50 Hz fundamental) can be troublesome .
Three-phase inverters are used for variable-frequency drive applications and for high power applications such as HVDC power transmission. A basic three-phase inverter consists of three single-phase inverter switches each connected to one of the three load terminals. For the most basic control scheme, the operation of the three switches is coordinated so that one switch operates at each 60 degree point of the fundamental output waveform. This creates a line-to-line output waveform that has six steps. The six-step waveform has a zero-voltage step between the positive and negative sections of the square-wave such that the harmonics that are multiples of three are eliminated as described above. When carrier-based PWM techniques are applied to six-step waveforms, the basic overall shape, or envelope, of the waveform is retained so that the harmonic and its multiples are cancelled.
The active filter with the Fuzzy logic Control (FLC) is proposed in this paper to suppress harmonic resonances in the distribution power system. The fuzzy control is implemented by various parallel band-pass filters tuned at harmonic frequencies so that the active filter can operate as an approximately pure harmonic conductance. Harmonic distortion by this control is drastically reduced .in order to cope with load change and system variations in distribution system a separate and tuning conductance for different harmonic frequency is also realized. The contributions of this paper are summarized as follows. Due to controlling delay, the damping active filter may unintentionally induce harmonic resonance at other locations in the feeder. This phenomenon is analyzed by using harmonic distributed-parameter model.
Three-phase four-wire distribution power systems have been widely applied to low-voltage applications; however, they encounter serious problems of harmonic current pollution and large neutral-line current. In this paper, a new hybrid power conditioner, composed of a hybrid power filter and a neutral- line current attenuator, is proposed. In the proposed hybrid power conditioner, the power capacity of power converters in the hybrid power filter and neutral-line current attenuator can be effectively reduced, thus increasing its use in high-power applications and enhancing the operation efficiency. A prototype is developed and tested. Experimental results verify that the proposed hybrid power conditioner can suppress the harmonic currents and attenuate the neutral-line current effectively whether the loads are balanced or not. Hence, the proposed hybrid power conditioner is an effective solution to the problems of harmonic currents and neutral-line current in three-phase four-wire distribution power systems. Besides, the output current of the three-phase power converter is much smaller than the conventional hybrid power filter, and the power rating of the zig- zag transformer is smaller than the rating of the conventional neutral-line current attenuator.
A solution of β -naphtol (100 mg, 0.69 mmol), benzaldehyde (105 µl, 1.03mmol), ethylenediamine (92 µl, 1.38 mmol) in 10 ml of ethanol wasstirring for 72 h to room temperature. The reaction mixture was evaporatedto a smaller volume. After the mixture was diluted with water and extractedwith chloroform. The organic phase was evaporated to dryness underreduced pressure, the residue was purified by crystallization frommethanol:water (4:1) yielding 75 % of product, m.p. 52-54 o C; IR } =3530, 3330, 3310 cm -1 ; 1 H NMR