Top PDF Unified Power Quality Conditioner for voltage and current compensation

Unified Power Quality Conditioner for voltage and current compensation

Unified Power Quality Conditioner for voltage and current compensation

This paper deals with a Unified Power Quality Conditioner (UPQC) for load balancing, power factor- correction, voltage regulation, voltage and current harmonics mitigation, mitigation of voltage sag, swell and voltage dip in a three-phase three-wire distribution system for different combinations of linear and non- linear loads.The unified power quality conditioner (UPQC) is a combination of back to back connected shunt and series active power filters (APFs) to a common DC link voltage, which compensates voltage and current based distortions, independently.Using instantaneous active and reactive Power theory ,harmonic detection, reactive power compensation, voltage sag and swell have been simulated and the results are analyzed. The operation and capability of the proposed system was analyzed through simulations with MATLAB / SIMULINK.
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FLC based adjustable speed drives for power quality enhancement

FLC based adjustable speed drives for power quality enhancement

Programmed PWM is basically the MMSR scheme in which different output fundamental amplitudes, the switching angles are computed off-line and stored readily for use. This scheme requires many wave-forms to be stored in memory for previous values of output fundamental magnitude [8]. Multiple Pulse Modulation with Selective Elimination of Harmonics is based on the principle of selecting suitable M pulse positions per quarter cycle to eliminate any M harmonics and obtaining output voltage variation by controlling the pulse width symmetrically around the pulse position. But this involves complex computations for obtaining the pulse position for various output amplitudes. A unified approach for generating pulse width modulation patterns for three- phase voltage source inverter that provides unconstrained selective harmonic elimination and fundamental current control [9]. The requirement of Z-source network has been discussed in [10], which should not differ much from the traditional drives.
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Augmentation of Real & Reactive Power in Grid by Unified Power Flow Controller

Augmentation of Real & Reactive Power in Grid by Unified Power Flow Controller

This project presents power flow control in transmission line with respect to voltage condition (L-G, L-L-G, L-L) over come by using unified power flow controller. The existing system employs UPFC with transformer less connection with both series and shunt converter. This converter have been cascaded with multilevel inverters which is more complicated to enhance the performance of UPFC. A proposed system consists of three terminal transformer for shunt converter and six terminal transformer for series converter. Shunt converter & series converter is coupled with common DC capacitor. DC link capacitor voltage is maintained using PID controller and synchronous reference frame theory (SRF) is used to generate reference voltage & current signal. Simulation studies are carried out for(L-G, L-L-G, L-L real & reactive power compensation)
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Power Quality Improvement And Mitigation Of Voltage Sag And  Current Swell Using Distributed Power Flow Controller

Power Quality Improvement And Mitigation Of Voltage Sag And Current Swell Using Distributed Power Flow Controller

Modern power utilities have to respond to a number of challenges such as growth of electricity demand specially in non-linear loads in power grids, consequently, That higher power quality should be considered. In this paper, DPFC which is similar to unified power flow controller (UPFC) in structure, which is used to mitigate the voltage sag and swell as a power quality issue. Unlike UPFC, the common dc-link in DPFC, between the shunt and series converter devices should be eliminated and three-phase series converter is divided to several single- phase series distributed converters through the power transmission line. And also to detect the voltage sags and find out the three single-phase reference voltages of DPFC, the synchronous reference frame method is proposed. Application of DPFC in power quality enhancement is simulated in Mat lab/Simulink environment which show the effectiveness of the proposed structure
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Improvement of Voltage Quality in Isolated Power Systems by Using Series Compensation

Improvement of Voltage Quality in Isolated Power Systems by Using Series Compensation

source impedance (ZS) is assumed to be 0.05 p.u. and .q=20 the main load converter is assumed to be a six- pulse controlled rectifier. The dc motor, as shown in Fig. 4, has Ra=2ohm and La=25mH. The rating of the dc load is 2 kW and it is also the base value chosen for the system. The current of the motor is controlled and load change is simulated by changing (Iref) the of the motor. The capacity of the sensitive load is assumed to be0.2 kVA (i.e.,) k=10 and its power factor at the fundamental frequency is 0.75 leading. The sensitive load level is assumed to be at full load in these examples. The SC was modeled as a PWM inverter and its detail model is given in [13]. A capacitor is used as the ESS. The simulations were accomplished using MATLAB. The voltage at the sensitive load terminals is as shown in Fig. 7 when a load change occurs but without the SC in service. Before the load change, the motor drive is at 0.5-p.u. loading and it can be shown that VL has a THD level of 30%.Fig. 8 shows the corresponding waveforms when the SC is in-service. With harmonics compensation by the SC, the sensitive load is protected against the harmonic distortion and the THD of the voltage has been significantly reduced to 3%.
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A New Method of Reference Signal Generation Applied To UPQC-PHEV For Grid Integration of WECS-SCIG

A New Method of Reference Signal Generation Applied To UPQC-PHEV For Grid Integration of WECS-SCIG

In this paper a Unified Power Quality Conditioner (UPQC) has been investigated for power quality enhancement and voltage faults/disturbances which occur in wind farm (WECS-SCIG) connected to grid. UPQC is an hybrid filter and it is combination of Series APF and Shunt APF which is used to compensate voltage disturbances and current distortion respectively. The real and reactive power compensation is provided by UPQC-PHEV. This control is achieved by generation of new reference signals which are generated by Fuzzy Logic Controller (FLC). The voltage sag occurs]in time interval between 1 to 1.5 sec which is compensated by Series APF part of UPQC. FLC will provide fast and dynamic response whenever fault occurs in system. Thus proposed system UPQC-PHEV-FLC improves power quality and voltage disturbances issues in grid connected WECS-SCIG and also compensation of active and reactive power.
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Control Strategy of Three Phase Shunt Active Power Filter for Power Quality Improvement

Control Strategy of Three Phase Shunt Active Power Filter for Power Quality Improvement

ABSTRACT: The increasing use of power electronics-based loads (adjustable speed drives, switch mode power supplies, etc.) to improve system efficiency and controllability is increasing the concern for harmonic distortion levels in end use facilities and overall power system. The application of passive tuned filters creates new system resonances which are dependent on specific system conditions. In addition, passive filters often need to be significantly over-rated to account for possible harmonic absorption from the power system. Passive filter ratings must be coordinated with reactive power requirements of the loads. Parallel (or shunt) active filters have been recognized as a valid solution to current harmonic and reactive power compensation of non-linear loads. The basic principle of Shunt Active Power filter is that it generates a current equal and opposite in polarity to the harmonic current drawn by the load and injects it to the point of coupling thereby forcing the source current to be pure sinusoidal. The control strategy is Synchronous Detection Algorithm. This technique relies in the fact that the three phase currents are balanced. The average power is calculated and divided equally between the three phases. The signal is then synchronized relative to the mains voltage for each phase. Then the desired reference current is evaluated.
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Voltage Stability Enhancement and Efficiency Improvement of Nigerian Transmission System Using Unified Power Flow Controller

Voltage Stability Enhancement and Efficiency Improvement of Nigerian Transmission System Using Unified Power Flow Controller

Compensation could be shunt whereby the compensating device is connected in parallel with the circuit to be compensated. It can be capacitive (leading) or inductive (lagging) reactive power, although in most cases, compensation is capacitive. Shunt compensation is successful in reducing voltage drop and power loss problems in the network under steady load conditions as it reduces the current flow in areas of installation [12][13]. It could also be series whereby the compensating device is connected in series with the circuit to be compensated. Whereas shunt compensation reduces the current flow in areas of installation, series compensation acts directly on the series reactance of the line. It reduces the transfer reactance between supply point and the load and thereby reduces the voltage drop [14].
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A Novel Control Method for Unified Power Quality Conditioner Using Nine-Switch Power Conditioner

A Novel Control Method for Unified Power Quality Conditioner Using Nine-Switch Power Conditioner

Section III then proceeds to compare the ratings and losses of the back-to-back and nine-switch conditioners, before an appropriate modulation scheme is evaluated in Section IV for reducing the nine-switch converter commutation count, and hence its switching losses. Also presented in Section IV is two sets of higher level control schemes with the first used for controlling one set of three-phase outputs so as to compensate for harmonic currents, reactive power flow and three-phase unbalance caused by nonlinear loads. The grid currents drawn from the utility are then sinusoidal, having only fundamental component. In synchronism, the second set of outputs is controlled to compensate for any detected grid voltage harmonics and unbalance, so that only a set of balanced three-phase voltages appears across the loads under normal operating conditions [17]. During voltage sags, the second set of control schemes also has the ability to continuously keep the load voltages within tolerable range. This sag mitigation ability, together with other conceptual findings discussed in this paper but not in the open literature, has already been verified in experiment with favorable results observed.
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A NOVEL HIGH PRECISION LOW POWER CURRENT MODE CMOS WINNER-TAKE-ALL CIRCUIT

A NOVEL HIGH PRECISION LOW POWER CURRENT MODE CMOS WINNER-TAKE-ALL CIRCUIT

of the other cells entire into ohmic and cut-off region respectively. With inclusion of current source and suitably choosing the transistor parameters, Fang [6] improved the resolution. However in et. al. Fang [6] winning is all depending upon the rate of the growth of the winning cell as compare to the other contending cells, no extra inhibitory circuit to inhibit the loser cell more faster. We proposed a novel cell where we introduced an inhibitory feedback along with the exitory feedback in order to inhibits other cell more faster.

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Simulation of generalized hybrid model for solar and wind power generation

Simulation of generalized hybrid model for solar and wind power generation

Due to urbanization, globalization and industrialization the demand for energy is rapidly increasing allows the world and India is not an exception. Out of all energies electrical energy is playing a major role in developed as well as developing countries. The energy is mostly produced by fossil fuels which are developing day his is to by day .they also produce lot of pollutants which totally damage the environment the alternative to this is to encourage renewable energy source. Now days the energy production at domestic level is becoming popular with the help of solar and wind energies . These technologies are widely used now days in the present paper an attempt has been made to simulate a generalized hybrid model including solar and wind.
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Voltage Mode-to-Current Mode Transformation

Voltage Mode-to-Current Mode Transformation

Current-mode (CM) filters are attractive because of their wider bandwidth, higher slew rate, wider dynamic range and lower power consumption compared to voltage-mode (VM) counterparts [1]. However, a large number of op-amp (OA)-based VM circuits with excellent performance and their elegant realization procedures were put forward in the past [2, 3]. It is, therefore, worthwhile to convert them into CM circuits. FTFN (Four terminal floating nullor) [4-10], CC (current conveyor) [11-14] and CFA (Current Feedback Amplifier) [15-22] based CM circuits have received considerable attention in many filtering and signal processing applications, particularly, the CFA-based circuits are attractive due to the high slew rate and bandwidth independent of closed loop gain. In this paper, FTFN- CC- and CFA-based CM circuits are obtained by transforming a class of OA- based VM circuits. Obviously, one type of circuit can then be converted into the other type through the proposed transformation. Similar attempts were made in the past to convert OTA-C (operational trans-conductance amplifier) circuits into CFA-based RC circuits [23] and from SAB (single amplifier biquad) circuit to current amplifier based biquad [24].
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Fast and slow voltage modulation of apical Cl

Fast and slow voltage modulation of apical Cl

Figure 5B is constructed with the same data as Figure 5A, but with the current plot- ted as a function of voltage. In order to describe the I vs V relations we assumed each cycle as beginning at V = -100 mV then going to +100 mV and then back to -100 mV. The plots were generated in a clockwise direction. As such we define an ongoing phase from -100 to +100 mV and a returning phase from +100 to -100 mV. The following points are to be noted in Figure 5B: 1) There was pronounced rectification at positive volt- ages on both ongoing and returning legs. 2) The ongoing leg of the curve did not coin- cide with the returning leg. The lack of a large phase difference between current and voltage (the extreme values of current and of voltage coincide on both extremes) suggests that the contribution of the capacitive im- pedance is minimal up to this frequency. As such, the existence of different pathways for the ongoing and returning legs on the I vs V figure points to a hysteresis effect, i.e., at a given voltage, the electrical resistance of the skin in the ongoing phase of the curve differs from that at the returning phase. It can be easily noticed that the hysteresis was more marked in the positive voltage range, as ex- pected from previous observations showing that positive apical voltages inhibit Cl - per- meability. 3) The I vs V figures obtained in consecutive cycles exactly overlapped (data not shown). 4) The returning leg of the I vs V curve resembled the instantaneous I vs V relations obtained with the voltage pulse experiments at 200-600 ms.
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Effect of welding parameters of Gas Metal Arc welding on weld bead geometry: A Review

Effect of welding parameters of Gas Metal Arc welding on weld bead geometry: A Review

Juan Wang and Yajiang LI [25] studied microstructure characterization in weld metals of high strength steels. Microstructural characterization of the weld metals of high strength steels welded under 80% Ar+20%CO2 GMAW and different weld heat inputs was carried out by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The relative contents of acicular ferrite and pro eutectic in the weld metals were evaluated by means of micro image analyzer. They observed that there was acicular ferrite in the grain and some pro eutectic ferrite on the boundary of original austenite grains when the weld heat input was small (9.6 kj/cm), but the microstructure was ferrite side plate when the heat input was larger (22.3 kj/cm).
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Conferência EPE PEMC 09 2006

Conferência EPE PEMC 09 2006

The testing system of distance relay consists in computer equipment, controller I/O interface and power amplifiers (Figure 1). In the computer equipment there is a simulator that provides several choices for the fault type. According the fault type it is generated the test signals that are converted in current and voltages references for the power amplifiers controllers. This is done using a microcontroller to connect the digital simulator to the power amplifiers.

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Modelling of Non-Linear Pilot Disinfection Water System: A Bond Graph Approach

Modelling of Non-Linear Pilot Disinfection Water System: A Bond Graph Approach

Known that the determination of UV dose (the UV light dose is defined as UV intensity multiplied by time: duration of exposition water to UV irradiations) is one of interesting parameters allowing the accomplishment of optimal water disinfection [1-3]. A better control of a water quality can be achieved by developing a robust mathematical model. However modelling the disinfection kinetics is a difficult task due to the complexity of the treatment process. The complex physical, biological and chemical processes involved in wastewater treatment process exhibit non linear behaviours which are difficult to describe. The UV lamp presents also a complicated model, indeed the radiant energy flux emitted by the discharge-gas lamp and the arc voltage are a complex functions of the current and time [4,5]. In fact, they depend on the lamp geometrical characteristics, gas type and pressure. We carried out a thorough study in order to found useful ballast, UV lump model and the water disinfection kinetics. Where [2] develops G-model of a discharge lamp, [4] use resistive approximation with three deviation from the linear model. In [5] the cubic approximation model and [6] develop a model with tangential approximation.
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Harmonic Mitigation in a Single Phase Non-Linear Load Using SAPF with PI Controller

Harmonic Mitigation in a Single Phase Non-Linear Load Using SAPF with PI Controller

Power Quality is a major consideration in all office equipments, industries and residential home appliances. Harmonics play a vital role in power quality issues. A harmonic is generated and deteriorating the quality of power due to non-linear load, which is connected to the electrical system. Based upon the load, there will be an increase in harmonic voltage and currents in the system, which will affect the whole system. The limitations for harmonic voltages and harmonic currents have defined in IEEE 519 and IEC standards. That limitation can be achieved by using shunt Active Power Filters. This paper deals on shunt active power filter with PI controller. Shunt active power filter (SAPF) is designed by employing voltage source inverter with pulse width modulation (PWM). For R-L non linear load this harmonic mitigation is done. The MATLAB / SIMULINK model of this system is si- mulated and results are obtained through THD analysis.
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ANALYSIS OF THE OPERATION OF A MICROGRID WITH RENEWABLE DISTRIBUTED GENERATION

ANALYSIS OF THE OPERATION OF A MICROGRID WITH RENEWABLE DISTRIBUTED GENERATION

In islanding mode, to synchronize the backup generator with the microgrid, the generator output voltage and frequency must comply with parameterized limits. During this mode, the system voltage depends on the generator voltage when it is running. With regard to the frequency, the bi-directional inverter implements an automatic frequency adjustment in order to prevent malfunction of frequency-sensitive loads (SMA, 2007). In addition, the output power of other source devices may be individually limited in case the upper and lower frequency limits are not complied. This kind of situation arises, for instance, when the battery bank is fully charged and the power from available renewable sources exceeds the power required by the loads. To prevent the overcharging of the battery, the bi-directional inverter changes the microgrid frequency. This frequency adjustment is monitored by the inverters of the distributed generation systems and, as soon as the grid frequency increases beyond a 51 Hz, they decrease their output power linearly in order to bring the frequency back to the rated frequency of the grid. This process, called “Frequency-Shift Power Control”, ends whenever the microgrid frequency reaches 52 Hz (SMA, -). The inverters become inactive, i.e., are disconnected from the microgrid, if the frequency outranges the 50 Hz ±4,5 Hz.
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Sba Controle & Automação  vol.22 número4

Sba Controle & Automação vol.22 número4

Many research groups have been working on digital pro- tection of transmission lines. Much attention has been paid to distance relaying techniques lately (Osman and Malik, 2001; Sidhu et al., 2002). Among many ap- proaches considered, transmission line protection based on the fundamental frequency signals is widely used. Ba- sically, the objective of a relaying scheme is to estimate the fundamental frequency components from the cor- rupted voltage and current signals following the fault oc- currence. For distance relaying, these fundamental com- ponents are used to determine the apparent impedance (Phadke and Thorp, 1988). According to the calculated impedance, the fault is identified as internal or external to the protection zone.
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J. Braz. Chem. Soc.  vol.23 número3

J. Braz. Chem. Soc. vol.23 número3

This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal:carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L -1 H
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