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Mitigation of electric arc furnace disturbances using the unified power quality conditioner
Abstract
This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC comprises combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy of the UPQC is presented. Since voltages at the point of common coupling (PCC) contain low frequency interharmonics, conventional methods cannot be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using active power processing to generate sinusoidal waveforms. Current compensating signals are detected based on current vector mapping on a rotating reference frame constituted by instantaneous phase voltages. A real system is simulated using a three-phase EAF model. Simulation results are presented to verify the control strategy and to assess the performance of UPQC in improving quality of power.
... UPQC consists of combined series and shunt active power filters [20]. The main function of UPQC includes [21][22][23][24][25]: (i) Reactive power compensation. (ii) Voltage regulation. ...
Classically, the aim of the electric power system is to generate electrical energy and to deliver this energy to the end-user equipment at an acceptable voltage. As nonlinear loads draw harmonic and reactive power components of current from ac mains, the quality of power deteriorates. This paper presents a review of the main power quality (PQ) problems with their associated causes and solutions with codes and standards. This paper concludes with some solutions to mitigate the Power Quality problems are presented.
... The synchronous reference frame (SRF) theory is developed in time-domain based reference current/voltage generation technique. The SRFT is performing the operation in steady-state or transient state as well as for generic voltage and current and capable of controlling the active power filters in real time system [15] , [18], [20], [21], [27], [28], [51], [54], [57], [58], [76], [77], [82], [104], [106], [111], [115], [120], [121], [125], [127], [128], [130], [131], [133], [134], [137], [141], [142], [150], [153], [155], [160], [167], [177], [178], [179], [180], [182], [187], [189], [190], [195], [204], [203], [207], [213], [214], [217], [218], [219]. One of the important characteristics of this theory is the simplicity of calculation because it involves only algebraic calculation. ...
Electrical power quality (EPQ) in distribution systems is a critical issue for commercial, industrial and residential applications. The new concept of advanced power electronic based Custom Power Devices (CPDs) mainly distributed static synchronous compensator (D-STATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC) have been developed due to lacking the performance of traditional compensating devices to minimize power quality disturbances. This paper presents a comprehensive review on D-STATCOM, DVR and UPQC to solve the electrical power quality problems of the distribution networks. This is intended to present a broad overview of the various possible DSTATCOM, DVR and UPQC configurations for single-phase (two wire) and three-phase (three-wire and four-wire) networks and control strategies for the compensation of various power quality disturbances. Apart from this, comprehensive explanation, comparison, and discussion on D-STATCOM, DVR, and UPQC are presented. This paper is aimed to explore a broad prospective on the status of D-STATCOMs, DVRs, and UPQCs to researchers, engineers and the community dealing with the power quality enhancement. A classified list of some latest research publications on the topic is also appended for a quick reference.
... The author proposes to install SVC or filter near the arc furnace to reduce 3 rd , 5 th and higher order harmonics. [17] discussed the use of Unified Power Quality Conditioner (UPQC) to improve the power quality of the power system connected with electric arc furnace. Series capacitor, series inductor, SVC, passive filter and custom devices such as DVR or DSTATCOM are few compensating devices to improve the power quality of the power system. ...
... UPQC consists of combined series and shunt active power filters [20]. The main function of UPQC includes [21][22][23][24][25]: (i) Reactive power compensation. (ii) Voltage regulation. ...
Classically, the aim of the electric power system is to generate electrical energy and to deliver this energy to the end-user equipment at an acceptable voltage. As nonlinear loads draw harmonic and reactive power components of current from ac mains, the quality of power deteriorates. This paper presents a review of the main power quality (PQ) problems with their associated causes and solutions with codes and standards. This paper concludes with some solutions to mitigate the Power Quality problems are presented.
... The UPQC has evolved to be one of the most comprehensive custom power solutions for power quality issues relating to non-linear harmonic producing loads and the effect of utility voltage disturbance on sensitive industrial loads [7]. UPQC consists of two Insulated Gate Bipolar Transistor (IGBT) based Voltage Source Converters (VSC), one shunt, and one series cascaded by a common Direct Current (DC) bus. ...
The purpose of this paper is to study on the effects of Distributed Generation (DG) towards unified power quality conditioner (UPQC) performance in mitigating voltage sags. The interest in DG has been increasing rapidly because DG might play an important role in the future power system. This paper will focus on the analysis of the comparison in the distribution system before and after the occurrence of mitigating voltage sags based on different type of phase to ground fault. This paper also will focus on the analysis of the effectiveness and efficiency in mitigating the voltage sags. The type of faults is analyzed using PSCAD simulation to observe the effectiveness and efficiency of the UPQC. Throughout this simulation, voltage sags problem can be solved and mitigated to decrease losses.
... The unified power quality conditioner (UPQC) has been widely studied to compensate for the disturbances of source voltages and load currents simultaneously. The UPQC has been applied to the compensation of voltage fluctuations related to nonperiodic waveforms in recent years [7][8][9][10][11]. In addition, some recent UPQC topologies have been proposed, such as UPQC with distributed generation [12], MC-UPQC [13], and modular UPQC [14], for solving power quality problems at the PCC. ...
This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to singlephase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.
... The unified power quality conditioner (UPQC) has been widely studied to compensate for the disturbances of source voltages and load currents simultaneously. The UPQC has been applied to the compensation of voltage fluctuations related to nonperiodic waveforms in recent years7891011. In addition, some recent UPQC topologies have been proposed, such as UPQC with distributed generation [12], MC-UPQC [13], and modular UPQC [14], for solving power quality problems at the PCC. ...
This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to single-phase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.
... In the previous studies, the control algorithms for current and voltage compensators were often based on the assumption that the load currents and the source voltages were periodic. The USPAF systems have been applied to the compensation of voltage fluctuations related non-periodic waveform in recent years [6,10,202122. Different non-active power theories in the time domain have been discussed in [23]. ...
... The Unified Power Quality Conditioner (UPQC) has evolved to be one of the most comprehensive custom power solutions for power quality issues relating to non-linear harmonic producing loads and the effect of utility voltage disturbance on sensitive industrial loads [1][2][3][4][5][6][7][8][9][10][11][12][13]. A UPQC is a combination of shunt and series compensation and is designed to cater for multiple power quality problems. ...
The unified power quality conditioner (UPQC) is one of the major custom power solutions, which is capable of mitigating the effect of supply voltage sag at the load end or at the point of common coupling (PCC) in a distributed network. It also prevents the propagation of the load current harmonics to the utility and improves the input power factor of the load. The control of series compensator (SERC) of the UPQC is such that it injects voltage in quadrature advance to the supply current. Thus, the SERC consumes no active power at steady state. The other advantage of the proposed control scheme is that the SERC can share the lagging VAR demand of the load with the shunt compensator (SHUC) and can ease its loading. The UPQC employing this type of quadrature voltage injection in series is termed as UPQC-Q. The VA requirement issues of SERC and SHUCs of a UPQC-Q are discussed. A PC-based new hybrid control has been proposed and the performance of the UPQC-Q is verified in a laboratory prototype. The phasor diagram, control block diagram, simulations and experimental results are presented to confirm the validity of the theory.
The paper presents the design, modelling and simulation of UPQC to improve the power quality in Thirty Bus system. Growing demand in industries emphasize power quality due to substantial presence of Power electronics as well as non-linear loads. Electrical power quality is affected by so many factors especially like presence of harmonics both voltage and current, sag and swell due to the switching loads etc. In order to maintain controlled power quality regulations, compensation at power levels is becoming an important practice. As power transfer grows, the power system becomes increasingly more complex to operate and the system becomes less secure. It may leads to large power flows with inadequate control. Thus the full potential of transmission interconnections cannot be utilized. FACTS technology is essential to alleviate these difficulties. At the distribution level, UPQC is on such solution to compensate major power quality issues and problems. The UPQC system is displayed using the elements of Simulink and it is simulated using MATLAB software. The simulation results are presented in time domain. Real and reactive power flows are compared with and without UPFC for system performance.
The aim of this paper is to present the implementation of a shunt Active Power Filter (APF) to reduce the harmonic distortion in the current of a voltage node feeding a nonlinear load. A two-level three-phase Voltage Source Inverter (VSI) is used for the APF. The control methodology employed is based on a high order sliding mode algorithm known as Super-Twisting. Simulation results are presented that confirms validity of the proposal.
This paper presents a new control method to compensate source voltage and load current harmonics and improvement of power quality problems through a three-phase unified power quality conditioner (UPQC). The UPQC system consists of combined operation of series and shunt active power filters sharing a common DC link. Paralel Active Power Filter (PAF) used for current harmonics, unbalanced and neutral current compensation; Series Active Power Filter (SAF) used for compensation of source voltage harmonics, unbalanced voltage and sag and swell of source voltage. The performance of the proposed control system was analyzed using simulations with Matlab/Simulink program, and experimental results with the hardware prototype. The proposed UPQC control algorithm can improve the power quality at the point of common coupling (PCC) on power distribution system.
This work deals with design, modelling and simulation of UPQC in Fourteen bus system to improve the power quality in a multi bus system. The UPQC system is modelled using the elements of Simulink and it is simulated using MATLAB. A sag is created by applying a heavy load at the receiving end. The sag is compensated by using the UPQC. The harmonics required at the receiving end are supplied by the inverter part of UPQC. The DC required by the UPQC is supplied by Solar cell and Boost converter system. The simulation results of fourteen bus system are presented in time domain.
In this paper unified power quality conditioner (UPQC) is being used as a universal active power conditioning device to mitigate both current as well as voltage harmonics at a distribution end of power system network. The performance of UPQC mainly depends upon how quickly and accurately compensation signals are derived. The determination of voltage references for series active power filter is based on a robust three phase digital phase locked loop (PLL) system using fuzzy regulator. Control strategies related to fuzzy hysteresis band voltage and current control methods, where the band is modulated with the system parameters to maintain the modulation frequency nearly constant are developed. The FLC-based compensation scheme eliminates voltage and current magnitude of harmonics with good dynamic response. The effectiveness and flexibility of the proposed system confirmed by Matlab/Simulink simulations.
Power quality has turned into a vital component in power systems, for consumer and household applications with wide usage of different electric and electronic equipments. The primary causes of a poor power quality are harmonic currents, supply-voltage variations and so forth. UPQC is a unique device which compensates harmonic currents and mitigates voltage variations at load side. This paper presents Synchronous Reference Frame control technique for UPQC to compensate power quality problems. Hysteresis Current Controller is used for generation of switching pulses to series and shunt APF's. Simulations are carried out in Matlab/Simulink for a three phase three wire system under distorted supply voltage and non-linear unbalanced load conditions. Simulation results prove that under unbalanced and nonlinear load conditions, UPQC eliminates the effect of supply voltage variations and harmonic currents on the power line.
Aiming at the existing strong coupling problem of UPQC model in synchronous rotating coordinate system, in order to realize the control process easily and accomplish the complete decoupling, two-phase coordinate system α-β was introduced to the complete decoupling PI control of voltage and current compensation unit. According to the corresponding mathematical model, the topology map of voltage and current compensation unit was gained. Direct single closed-loop control method was used, meantime, parameter was set and the structure chart of PI control unit was designed. Finally, the effectiveness and feasibility of the control method is proved by Matlab/Smulink simulation and hardware experiment.
In this paper, series and parallel compensators of STATCOM and DVR are introduced and the comparison of these two in compensating of power quality phenomena from electric arc furnace is provided. STATCOM is a shunt active filter and DVR is a series active filter. Method which has been selected for control of every one of these devices is an optimal control way that it minimizes power losses.
This paper presents novel control strategy of a three-phase four-wire unified power quality conditioner (UPQC). It is used to improve power quality in distribution system. The UPQC is realized by the integration of series and parallel active power filter (SAPF and PAPF) sharing a common dc bus capacitor. The realization of parallel APF and series APF are carried out using a three-phase, three legs voltage source inverter (VSI) with split capacitor. In both APFs the fundamental source voltages and currents are extracted by synchronous reference frame technique. SAPF connected with the supply by series transformer. The secondary of series transformer is affected by load side short circuits. This paper also explains the control circuit for protection of series transformer against over voltage and over current. PAPF connected with the system by series inductance. The performance of the applied control algorithm of shunt active filter with series active filter is evaluated in terms of power-factor correction, load balancing, and mitigation of voltage and current harmonics in a three-phase four-wire distribution system for non-linear load, unbalanced supply and load conditions . Sinusoidal PWM current controller, modulated hysteresis current controller are used for generation of switching pulses to series and parallel APFs. The two control algorithm is simulated by use of MATLAB/Simulink-based environment and the obtained results validated through experimental study with the UPQC hardware prototype.
This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA$_{\rm min}$. More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.
Power quality has become an important factor in power systems, for consumer and household appliances with proliferation of various electric and electronic equipment and computer systems. The main causes of a poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation at the load side, is compensated by unique device of UPQC presented in this paper and this paper presents a modified synchronous-reference frame (SRF)-based control method to Shunt active filter and instantaneous PQ (IPQ) theory based control technique for series active filter to compensate power-quality (PQ) problems through a three-phase four-wire unified PQ conditioner (UPQC) under unbalanced and distorted load conditions. The proposed UPQC system can improve the power quality at the point of common coupling on power distribution systems under unbalanced and distorted load conditions. The simulation results based on Matlab/Simulink are discussed in detail in this paper.
A new optimal control strategy for unified power quality conditioners (UPQC) is presented. This strategy is based on feedback linearisation. The UPQC consists of series and shunt converters, where the series converter usually works as a voltage source, and the shunt converter works as a current source. However, it is possible to use the series converter as a current source, and the shunt converter as a voltage source, as utilised in this study. As for this scheme, an optimal voltage angle at load terminals, in order to minimise the converter losses, is proposed. A comparison with the traditional UPQC, where series and shunt converters are considered to be voltage and current sources, respectively, is also presented.
This paper presents a new synchronous-reference-frame (SRF)-based control method to compensate power-quality (PQ) problems through a three-phase four-wire unified PQ conditioner (UPQC) under unbalanced and distorted load conditions. The proposed UPQC system can improve the power quality at the point of common coupling on power distribution systems under unbalanced and distorted load conditions. The simulation results based on Matlab/Simulink are discussed in detail to support the SRF-based control method presented in this paper. The proposed approach is also validated through experimental study with the UPQC hardware prototype.
This paper presents a new control method to compensate the power quality problems through a three-phase unified power quality conditioner (UPQC) under non-ideal mains voltage and unbalanced load conditions. The performance of proposed control system was analyzed using simulations with Matlab/Simulink program, and experimental results with the hardware prototype. The proposed UPQC system can improve the power quality at the point of common coupling (PCC) on power distribution system under non-ideal mains voltage and unbalanced load conditions.
This paper deals with unified power quality conditioner (UPQC),
which aims at the integration of series-active and shunt-active power
filters. The main purpose of a UPQC is to compensate for voltage
imbalance, reactive power, negative-sequence current and harmonics. This
paper discusses the compensation principle and control strategy of the
UPQC in detail. Experimental results obtained from a laboratory
prototype of 20 kVA are shown to verify the viability and effectiveness
of the UPQC
The application of deregulation policy in the power sector has emphasized the need for new tools, which are capable of tracking and mitigating the voltage disturbances caused by nonlinear loads. This paper introduces a new strategy to track and mitigate the voltage flicker and the unbalance produced by large AC arc furnaces. The mitigation strategy depends on an innovative technique for voltage disturbance extraction, which uses symmetrical components. This paper proves that The unified power quality conditioner (UPQC) is capable of suppressing the entire voltage disturbance in the industrial system. Results of digital simulation are presented to validate and verify the control strategy and to assess the performance of UPQC to mitigate the voltage flicker and the unbalance produced by AC arc furnace.
The power circuit of a general active power line conditioner
(APLC) is based on series and shunt power converters that share a single
DC link. In the present paper, a generic control concept for these
series and shunt converters is proposed. It is based on the
instantaneous real and imaginary power theory. In fact, the resulting
equipment deals with the custom power and FACTS concepts. This equipment
incorporates not only the compensation functions at the fundamental
frequency like a unified power flow controller (UPFC), but also provides
active harmonic mitigation capabilities. For these reasons, the
compensator proposed here is called the universal active power line
conditioner (UPLC). Simulation and experimental results are presented to
confirm that the new approach has better performance than those obtained
by controllers based on traditional concepts of active and reactive
power
This paper deals with a new control scheme for a parallel 3-phase
active filter to eliminate harmonics and to compensate the reactive
power of the nonlinear loads. A 3-phase voltage source inverter bridge
with a DC bus capacitor is used as an active filter (AF). A hysteresis
based carrierless PWM current control is employed to derive the
switching signals to the AF. Source reference currents are derived using
load currents, DC bus voltage and source voltage. The command currents
of the AF are derived using source reference and load currents. A
3-phase diode rectifier with capacitive loading is employed as the
nonlinear load. The AF is found effective to meet IEEE-519 standard
recommendations on the harmonics level
It is shown that a static VAR generator comprising a capacitive filter network and a thyristor-controlled inductor can effectively compensate for rapid and unbalanced load variations and is able to maintain system voltage and power factor, even under extremely adverse load conditions. The performance of such a static compensating system is, however, dependent on the principles of control employed, the adequacy of the VAR rating, and the electrical characteristics of the filter network. In arc furnace applications, the VAR generator must be rated for unbalanced load conditions and the capacitive filter network must be designed to be compatible with the ac system impedance, and with the spectrum of the furnace current that contains both odd and even harmonics.
The effect of a series inductor on the reduction of voltage
flicker in electric power systems supplying arc furnaces is assessed.
The arc furnace is simulated as a voltage generator with variable
amplitude during the melting process. The design of the inductor hinges
on the fact that, when connected into the electric power system, it
should not interfere with the production capacity of the plant itself.
The use of a powerful simulation program (EMTP) makes it possible to
study a large number of cases and therefore to determine the appropriate
size of the series inductor for the purpose of reducing voltage flicker.
The simultaneous presence of the series inductor with capacitors and/or
filters, with the purpose of limiting harmonic pollution and improving
the power factor, is also discussed
This paper deals with unified power quality conditioners (UPQCs), which aim at the integration of series-active and shunt-active power filters. The main purpose of a UPQC is to compensate for voltage flicker/imbalance, reactive power, negative-sequence current and harmonics. In other words, the UPQC has the capability of improving power quality at the point of installation on power distribution systems or industrial power systems. This paper discusses the control strategy of the UPQC, with a focus on the how of instantaneous active and reactive powers inside the UPQC. Experimental results obtained from a laboratory model of 20 kVA, along with a theoretical analysis, are shown to verify the viability and effectiveness of the UPQC
This paper presents a new control strategy for the shunt active filter in three-phase three-wire systems with zero sequence voltages. An extended method based on instantaneous power theory in a rotating reference frame is developed for extracting the compensating signals for highly/randomly varying loads. Since voltages at the point of common coupling contain low frequency interharmonics, conventional methods can not he used for dc voltage regulation. Therefore, a new method is introduced for this purpose. A three-phase electric arc furnace model is used to show power quality improvement through reactive power and harmonic compensation by a shunt active filter using the proposed method. Simulation results are provided to verify the system performance.
This study examines the thermal efficiency of the operation of arc
furnace and the effects of harmonics and voltage dips of a factory
located near Bangkok. It also attempts to find ways to improve the
performance of the arc furnace operation and minimize the effects of
both harmonics and voltage dips. A dynamic model of the arc furnace has
been developed incorporating both electrical and thermal
characteristics. The model can be used to identify potential areas for
improvement of the furnace and its operation. Snapshots of waveforms and
measurement of RMS values of voltage, current and power at the furnace,
at other feeders and at the point of common coupling were recorded.
Harmonic simulation program and electromagnetic transient simulation
program were used in the study to model the effects of harmonics and
voltage dips and to identify appropriate static and dynamic filters to
minimize their effects within the factory. The effects of harmonics and
voltage dips were identified in records taken at the point of common
coupling of another factory supplied by another feeder of the same
substation. Simulation studies were made to examine the results on the
second feeder when dynamic filters were used in the factory which
operated the arc furnace. The methodology used and the mitigation
strategy identified in the study are applicable to general situation in
a power distribution system where an arc furnace is a part of the load
of a customer
The DSTATCOM is a fast response, inverter-based power controller that provides flexible voltage control at the point of connection for improving the power quality in distribution systems. It can also provide instantaneous power factor correction to improve line utilization and minimize energy losses. The DSTATCOM is an alternating, synchronous voltage source connected in shunt (parallel) to the distribution three-phase feeder circuit via a coupling transformer. It can exchange reactive power with the distribution system by varying the amplitude and phase angle of an internal voltage source with respect to the line terminal voltage, resulting in controlled current flow through the coupling transformer. The DSTATCOM is a solid-state, DC to AC voltage-source inverter, utilizing advanced power semiconductor switching devices. It can effectively replace conventional voltage and VAr control elements, load tap changing transformers, voltage regulators and switched capacitors used in distribution systems. This paper presents the results of field tests conducted on the prototype model which was connected at a lumber mill for the purpose of mitigating running voltage flicker.
Since 1989, Union Electric has made use of series capacitor banks
to mitigate voltage flicker problems on long distribution feeders with
fluctuating loads. The types of loads being compensated for are cotton
gins, a water well pump, sawmills, and a dog food processing plant, with
the flicker typically being reduced by 60 to 80 percent. These series
capacitors have been designed, constructed, and installed by Union
Electric engineering and construction personnel at a cost comparable to
a shunt bank installation
This paper describes the system outline, the features of component equipments and the operating results of 120 MVA Static VAR Compensator (SVC). The SVC was installed for suppressing flicker caused by two 100 ton arc furnaces and has been in operation since April of 1978. In addition, an exclusive monitor panel was installed to monitor the flicker, harmonic currents and other components at critical bus. Special emphasis is placed on the analysis of flicker compensating effect with new measuring method, 33 kV thyristor switch hardware and outline of the monitor panel.
A new universal power quality manager is proposed. The proposal
treats a number of power quality problems simultaneously. The universal
manager comprises a combined series and shunt three-phase PWM controlled
converters sharing a common DC link. A control scheme based on fuzzy
logic is introduced and the general features of the design and operation
processes are outlined. The performance of two configurations of the
proposed power quality manager are compared in terms of a recently
formulated unified power quality index. The validity and integrity of
the proposed system is proved through computer simulated experiments
Short-term flicker severity (P<sub>st</sub>) is an important
electric power quality index defined by the International
Electrotechnical Commission (IEC). P<sub>st</sub> results from the
statistical evaluation of flicker over short periods of time producing
an objective measure for flicker originating from various types of
sources. This paper reviews previous methods for computing
P<sub>st</sub> and proposes a new iterative algorithm. The algorithm is
computationally efficient and shown to comply with the IEC
standard
A conventional three-phase electric arc furnace causes flicker at
the point of common coupling with AC mains. This generally occurs with
AC mains having a low short-circuit capacity. The flicker is caused by
flucluating reactive power consumption of the furnace. This paper
describes a way, through computer simulation, of increasing the dynamic
performance of the furnace and keeping reactive power consumption
constant. This can be achieved with the addition of a three-phase power
controller and a booster transformer to the power source and the
introduction of a new control method of regulating the reactive power
input. The problem of flicker can thus be minimized. This was
experimentally tested on a single-phase model and the results obtained
were very satisfying. Due to laboratory facilities, the three-phase
testing was not performed
The effectiveness of an active power filter depends basically on
three characteristics: (a) the modulation method used; (b) the design
characteristics of the PWM modulator; and (c) the method implemented to
generate the reference template. For the last characteristic there are
many methods, most of them complicated and hence difficult to implement
and adjust. In this paper, a new method, which has simplicity at its
main characteristic, is presented. The method is based on “sample
and hold” circuits, synchronized with the peak value of the
phase-to-neutral mains voltage. This method is useful for shunt active
power filters and is capable to eliminate harmonics, compensate power
factor, and correct unbalance problems simultaneously. It also has the
ability to slow-down sudden transient changes in the load. Experimental
results, with the reference template obtained with the method, are
presented in the paper
New functionalities of the unified power quality conditioner
- A Elnady
- M M A Salama