scholarly journals Power Balance and Power Factors of Distorted Electrical Systems and Variable Speed Asynchronous Electric Drives

Electronics ◽  
2021 ◽  
Vol 10 (14) ◽  
pp. 1676
Author(s):  
Viktor Petrushyn ◽  
Vasiliy Horoshko ◽  
Juriy Plotkin ◽  
Nurgul Almuratova ◽  
Zhanar Toigozhinova
Keyword(s):  
Power Factor ◽  
Electromagnetic Compatibility ◽  
Frequency Converter ◽  
Asynchronous Motor ◽  
Experimental Studies ◽  
Harmonic Distortion ◽  
Operating Mode ◽  
Measuring Instruments ◽  
Electrical Systems ◽  
Grid Side

In this study, power quality coefficients that determine the distortion of electrical systems are established. The power factor is chosen as a universal criterion for electromagnetic and electro-energetic compatibility of distorted sources and distorting loads. Mathematical expressions are obtained for its calculation in various cases of electrical systems distortion. As an application example, power balances and power factors of a variable frequency asynchronous drive system are considered. The criterion: the power factor not only determines the energy and electromagnetic compatibility of the drive with power supply, but it also evaluates drive efficiency. Experimental studies were carried out under usage of inexpensive, commonly used measuring devices both on the grid side of the frequency converter and on the asynchronous motor side. The studied coefficients were determined in two ways: measuring instruments and analysis of oscillograms. The second method for determining the above coefficients from oscillograms of currents and voltages also requires finding the total harmonic distortion (THD) of currents and voltages for the corresponding load adjusting points. The similarity of the obtained results shows that both of these methods can be applied. According to the operating mode of the load, the criterion is calculated as an average range in a certain range of speed control, or it is determined by considering a given tachogram of speed changes. The results of experimental studies confirm the correctness of the theoretical provisions.

scholarly journals On the Relation between Mains-Side Current THD and DC Link Voltage Loop Gain in Grid-Connected Unity Power Factor Operating Converters

2021 ◽  
Author(s):  
Alon Kuperman
Keyword(s):  
Power Factor ◽  
Dynamic Performance ◽  
Harmonic Distortion ◽  
Loop Gain ◽  
Unity Power Factor ◽  
Trade Off ◽  
Loop Bandwidth ◽  
Grid Connected Converters ◽  
Grid Side ◽  
Double Grid

<p>It is well-known that attainable DC link voltage loop bandwidth in grid-connected converters operating with unity power factor is limited due to trade-off with AC-side current total harmonic distortion (THD). The letter reveals that THD requirement directly imposes the value of voltage loop gain magnitude at double-grid frequency; therefore the dynamic performance may be improved without deteriorating the grid-side current quality by modifying the controller structure such that the loop gain magnitude at double-grid frequency and the crossover frequency are decoupled. Experimental results validate the revealed findings.</p>

scholarly journals Energy interaction of two-link converters of a multi-motor drive with mains supply

2021 ◽  
Vol 288 ◽  
pp. 01007
Author(s):  
Rishat Ganiev
Keyword(s):  
Power Consumption ◽  
Power Factor ◽  
Frequency Converter ◽  
Asynchronous Motor ◽  
Active Power ◽  
Total Power ◽  
Reactive Component ◽  
Electric Drives ◽  
Industrial Enterprises ◽  
Total Power Consumption

It is known that the total power electrical loads consume from the mains is the sum of their two components – active and reactive. Most electric drives of modern industrial enterprises consume up to 40% of reactive energy in relation to the total energy. This results in an increased full power consumption thereby increasing the load on the supply mains. Modern electric drives are built as follows: supply mains – rectifier-direct current link-inverter – asynchronous motor. The total power consumption is at the "mains-rectifier" interface, where the required active power factor of the converter can be formed. The higher the active power factor, the lower the reactive component in the total consumed energy. Thus, the paper proposes a solution to the problem of building highly efficient converting devices for powering electric motors with the required power factor. In particular, the paper discusses possible increase in the power factor of the electric drive mains input with two-link frequency converters based on active (controlled) rectifiers with current and voltage inverters. The author proposes new ways to control active rectifiers based on the use of AC rectifying devices with fully controlled GTO, GCT thyristors, as well as pulse-width control IGBT transistors. The paper offers options for the construction of these rectifiers and the results of modeling the proposed control methods, confirming a decrease in the passive components of the mains current, and, as a consequence, an increase in the mains input power factor. The simulation results were obtained in MathLab 10, and are the basis for confirming the method of increasing the active power factor at the mains input of a controlled two-link frequency converter.

scholarly journals On the Relation between Mains-Side Current THD and DC Link Voltage Loop Gain in Grid-Connected Unity Power Factor Operating Converters

2021 ◽  
Author(s):  
Alon Kuperman
Keyword(s):  
Power Factor ◽  
Dynamic Performance ◽  
Harmonic Distortion ◽  
Loop Gain ◽  
Unity Power Factor ◽  
Trade Off ◽  
Loop Bandwidth ◽  
Grid Connected Converters ◽  
Grid Side ◽  
Double Grid

<p>It is well-known that attainable DC link voltage loop bandwidth in grid-connected converters operating with unity power factor is limited due to trade-off with AC-side current total harmonic distortion (THD). The letter reveals that THD requirement directly imposes the value of voltage loop gain magnitude at double-grid frequency; therefore the dynamic performance may be improved without deteriorating the grid-side current quality by modifying the controller structure such that the loop gain magnitude at double-grid frequency and the crossover frequency are decoupled. Experimental results validate the revealed findings.</p>

scholarly journals A Novel Single-Switch Single-Stage LED Driver with Power Factor Correction and Current Balancing Capability

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1340
Author(s):  
Yih-Her Yan ◽  
Hung-Liang Cheng ◽  
Chun-An Cheng ◽  
Yong-Nong Chang ◽  
Zong-Xun Wu
Keyword(s):  
Power Factor ◽  
High Power ◽  
Pulse Width Modulation ◽  
Power Factor Correction ◽  
Harmonic Distortion ◽  
Boost Converter ◽  
Single Stage ◽  
Led Driver ◽  
Flyback Converter ◽  
High Power Factor

A novel single-switch single-stage high power factor LED driver is proposed by integrating a flyback converter, a buck–boost converter and a current balance circuit. Only an active switch and a corresponding control circuit are used. The LED power can be adjusted by the control scheme of pulse–width modulation (PWM). The flyback converter performs the function of power factor correction (PFC), which is operated at discontinuous-current mode (DCM) to achieve unity power factor and low total current harmonic distortion (THDi). The buck–boost converter regulates the dc-link voltage to obtain smooth dc voltage for the LED. The current–balance circuit applies the principle of ampere-second balance of capacitors to obtain equal current in each LED string. The steady-state analyses for different operation modes is provided, and the mathematical equations for designing component parameters are conducted. Finally, a 90-W prototype circuit with three LED strings was built and tested. Experimental results show that the current in each LED string is indeed consistent. High power factor and low THDi can be achieved. LED power is regulated from 100% to 25% rated power. Satisfactory performance has proved the feasibility of this circuit.

scholarly journals Hybrid Three-Phase Rectifiers with Active Power Factor Correction: A Systematic Review

Electronics ◽  
2021 ◽  
Vol 10 (13) ◽  
pp. 1520
Author(s):  
José Teixeira Gonçalves ◽  
Stanimir Valtchev ◽  
Rui Melicio ◽  
Alcides Gonçalves ◽  
Frede Blaabjerg
Keyword(s):  
Power Factor ◽  
Power Distribution ◽  
Harmonic Distortion ◽  
International Standards ◽  
Pwm Converter ◽  
High Power Factor ◽  
Three Phase ◽  
Sinusoidal Input ◽  
Converter Topologies ◽  
Future Direction

The hybrid three-phase rectifiers (HTR) consist of parallel associations of two rectifiers (rectifier 1 and rectifier 2), each one of them with a distinct operation, while the sum of their input currents forms a sinusoidal or multilevel waveform. In general, rectifier 1 is a GRAETZ (full bridge) (can be combined with a BOOST converter) and rectifier 2 is combined with a DC-DC converter. In this HTR contest, this paper is intended to answer some important questions about those hybrid rectifiers. To obtain the correct answers, the study is conducted as an analysis of a systematic literature review. Thus, a search was carried out in the databases, mostly IEEE and IET, and 34 papers were selected as the best corresponding to the HTR theme. It is observed that the preferred form of power distribution in unidirectional hybrid three-phase rectifiers (UHTR) is 55%Po (rectifier 1) and 45%Po (rectifier 2). For the bidirectional hybrid three-phase rectifiers (BHTR), rectifier 1 preferably takes 90% of Po and 10% of Po is processed by rectifier 2. It is also observed that the UHTR that employ the single-ended primary-inductor converter (SEPIC) or VIENNA converter topologies in rectifier 2 can present sinusoidal input currents with low total harmonic distortion (THD) and high Power Factor (PF), even successfully complying with the international standards. The same can be said about the rectifier that employs a pulse-width (PWM) converter of BOOST topology in rectifier 2. In short, the HTR are interesting because they allow using the GRAETZ full bridge topology in rectifier 1, thus taking advantage of its characteristics, being simple, robust, and reliable. At the same time, the advantages of rectifier 2, i.e., high PF and low THD, are well used. In addition, this article also points out the future direction of research that is still unexplored in the literature, thus giving opportunities for future innovation.

Some aspects of improving the energy efficiency of a mine centrifugal pumps.

2020 ◽  
Vol 23 (2) ◽  
pp. 48-51
Author(s):  
V. KONDRATENKO ◽  
◽  
V. KALYNYCHENKO ◽  
Keyword(s):  
Energy Efficiency ◽  
Mine Drainage ◽  
Experimental Studies ◽  
Operating Mode ◽  
Centrifugal Pumps ◽  
Pump Unit ◽  
Drainage Systems ◽  
Start Up ◽  
Discharge Unit ◽  
Pumping Units

Mine drainage systems, which are used at the main drainage of mining enterprises, have a drive capacity of up to 1600kW. To reduce non-productive energy losses, as well as for the continuous operation of the mining company, mine pumps must be energy efficient and reliable. Analysis of downtime of drainage systems shows that the weak point is the unloading device. This fact can lead not only to the failure of the pumping unit, but also to possible prolonged downtime of the mine. The main disadvantage of the existing disk unloading devices of mine pumps is their low reliability and low service life, due to the rapid wear of the components of the unloading unit. The most vulnerable elements of the unloading device are the unloading rings. The need for frequent replacement and adjustment of the elements of the discharge unit is associated with disassembly and assembly of the pump directly in the pump chamber. Such actions require significant costs of unproductive manual labor of service personnel, and rapid wear of parts of the unloading device necessitates their constant replenishment. Malfunctions in the unloading device can cause significant pump failures. To increase the reliability and energy efficiency of mine drainage systems, the method of control of the unloading device was used. During the experimental studies it was found that cavitation phenomena during the operation of pumping units are absent and, accordingly, can not be the cause of wear of the elements of the unloading unit. When the pumps are operating in steady state, the displacement of the rotors was monitored for 3-4 hours on each pump unit. After data processing, it was obtained that the wear of the surface of the unloading rings occurs at a rate of 0.05-0.15mm in one hour. To determine the wear of the rings of unloading during start-up - stop of the pump, at first the indicators of measuring devices at the established mode of operation of the pump unit were fixed. Then the pump was turned off and on again. After starting the pump unit, we made sure that the operating mode of the unloading device did not change and compared the readings of the shaft position indicator before stopping and after starting the pump. From the measurements made it followed that stopping and starting the pump does not lead to noticeable wear of the unloading device. Therefore, it can be assumed that mainly the wear of the discharge rings occurs during the steady operation of the pump unit.

Study of the Influence of Control System Parameters on the Quality of the Input Current of a Three-Phase Power Factor Corrector

2021 ◽  
Vol 2 (2) ◽  
pp. 29-35
Author(s):  
Dmitry A. Sorokin ◽  
◽  
Sergey I. Volskiy ◽  
Jaroslav Dragoun ◽  
◽  
...  
Keyword(s):  
Control System ◽  
Power Factor ◽  
Harmonic Distortion ◽  
Total Harmonic Distortion ◽  
Input Current ◽  
System Operation ◽  
Error Amplifier ◽  
Three Phase ◽  
Power Factor Corrector

The paper suggests a control system of a three-phase power factor corrector. The study of the control system operation is carried out and the expressions for calculating the permissible values of error amplifier factors are obtained. The influence of the error amplifier parameters on phase current quality is investigated. The dependence of total harmonic distortion input current on a combination of error amplifier parameters is obtained at a given value of power factor. The conditions under which the total harmonic distortion input current has the minimum value are found out. This article is of interest to power electronics engineers, who are aimed at developing a three-phase power factor corrector.

A 12-pulse rectifier with passive harmonic reduction based on UIPT in more electric aircrafts

Circuit World ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rohollah Abdollahi
Keyword(s):  
Power Factor ◽  
Harmonic Distortion ◽  
Cost Savings ◽  
Cost Effective ◽  
Industrial Applications ◽  
Input Current ◽  
New Combination ◽  
Content Type ◽  
Harmonic Reduction ◽  
Simulation Results

Purpose The purpose of this paper is to provide a T autotransformer based 12-pulse rectifier with passive harmonic reduction in more electric aircraft applications. The T autotransformer uses only two main windings which result in volume, space, size, weight and cost savings. Also, the proposed unconventional inter-phase transformer (UIPT) with a lower kVA rating (about 2.6% of the load power) compared to the conventional inter-phase transformer results in a more harmonic reduction. Design/methodology/approach To increase rating and reduce the cost and complexity of a multi-pulse rectifier, it is well known that the pulse number must be increased. In some practical cases, a 12-pulse rectifier (12PR) is suggested as a good solution considering its simple structure and low weight. But the 12PR cannot technically meet the standards of harmonic distortion requirements for some industrial applications, and therefore, they must be used with output filters. In this paper, a 12PR is suggested, which consists of a T autotransformer 12PR and a passive harmonic reduction (PHR) based on the UIPT at direct current (DC) link. Findings To show the advantage of this new combination over other solutions, simulation results are used, and then, a prototype is implemented to evaluate and verify the simulation results. The simulation and experimental test results show that the input current total harmonic distortion (THD) of the suggested 12PR with a PHR based on UIPT is less than 5%, which meets the IEEE 519 requirements. Also, it is shown that in comparison with other solutions, it is cost effective, and at the same time, its power factor is near unity, and its rating is 29.92% of the load rating. Therefore, it is obvious that the proposed rectifier is a practical solution for more electric aircrafts. Originality/value The contributions of this paper are summarized as follows. The suggested design uses a retrofit T autotransformer, which meets all technical constraints, and in comparison, with other options, has less rating, weight, volume and cost. In the suggested rectifier, a PHR based on UIPT at its dc link of 12PR is used, which has good technical capabilities and lower ratings. In the PHR based on UIPT, an IPT is used, which has an additional secondary winding and four diodes. This solution leads to a reduction in input current THD and conduction losses of diodes. In full load conditions, the input line current THD and power factor are 4% and 0.99, respectively. The THD is less than 5%, which satisfies IEEE-519 and DO-160G requirements.

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