Step-Up Asymmetrical Nine Phase Delta-Connected Transformer for HVDC Transmission (original) (raw)
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2012
The main idea of this paper is to build a 3/9 AC multiphase transformer for conversion into DC power through the rectifier circuit which contains 18 pulse rectification with a ripple factor less than 0.8% produced by the odd phase number 9. This modeling has been simulated using Orcad simulation software, the nine phases are out of the main three phase power lines, each phase is shifted from the other by 40 o (360 o /9), this type of
Electric Power Systems Research, 2020
In order to promote savings on installed filters in traditional HVDC transmission systems, and thus provide a less polluted power quality, this paper proposes a 24-pulse controlled converter that uses two identical three-phase three-winding special transformers, as well as four thyristor-controlled 6-pulse AC/DC converters connected in series. The configuration of the two transformers, and the necessary tap calculations are presented in order to achieve the 7.5°phase lag required to obtain the 24-pulse converter system. An analysis of the performance indices (power factor and Total Harmonic Distortion-THD) of both HVDC systems (traditional 12-pulse and the proposed 24-pulse) is performed and the results show improvements in the indices when using the proposed 24pulse system. Simulation analysis was performed using Matlab/Simulink software in order to validate the proposed 24-pulse converter for use in HVDC transmission systems, considering the operationality of the proposed system under normal and degraded operating conditions. A laboratory prototype was designed and executed based on transformers with extended delta primary windings to validate the proposed 24-pulse converter in terms of harmonic mitigation and improved power quality. The results confirm the viability and applicability of the proposed converter in HVDC transmission systems.
18-Pulse transformer device for flexible connection of asynchronous power systems
2017
Transmission of active power between power systems with the same nominal frequencies, linked via phase-rotating transformer is examined. The device is based on hexagonal scheme, and due to new proposal, provides symmetrical 18-phase output system of voltages, wherein the various phases of it are connected to different phases of three-phase receiving system by means of semiconductor switching elements, composed in two groups to reduce a quantity of switching keys. For reducing oscillations of transmitted active power, caused by 20° step switching of the phase angle between the voltages of the connected systems PWM modulation method is used, thus providing a smoother angle switching. It was shown, that increasing the number of phases sufficiently reduces the level of harmonic distortion of currents and voltages on the buses of receiving power system, so at some conditions the requirements, imposed on higher harmonics content in high voltage electrical networks could be met without the...
Abstract—The converter transformer is a vital equipment in HVDC transmission system. It serves as an isolating device between power transformer and dc link. In converter transformer primary is not much affected where as secondary is severely affected due to super imposed DC voltage with polarity reversal and short time over voltages. This paper mainly introduces causes for the improper operation of converter transformer and provides the improved solution to overcome harmonic reduction and improvement in the commutation process. The analysis is carried out in SIMULINK/MATLAB environment.
A 20-Pulse Asymmetric Multiphase Staggering Autoconfigured Transformer For Power Quality Improvement
IEEE Transactions on Power Electronics, 2017
This letter presents a 20-pulse multi-phase staggering autoconfigured transformer (MSAT) for power quality improvement in medium and high power applications. The proposed autoconfigured transformer is a combination of delta and zigzag transformers. Contrary to the prior art multi-pulse autoconnected transformers, magnetic rating of the proposed configuration is only 40% of the load rating in addition to improved power quality indices. Moreover, the creation of neutral point ascribed to inbuilt zigzag windings supplements as one of the remarkable advantages of the proposed MSAT. Therefore, with this suggested configuration, the performance of zigzag transformer is accomplished within the autoconfigured transformer. A detailed comparison of the proposed MSAT configuration with that of other multi-pulse autoconnected transformers in terms of magnetic rating and power quality indices are presented. Further, the feasibility and operability of the proposed MSAT are verified and validated through experimental tests on the laboratory prototype. The test results so obtained complies with the IEEE-519 and IEC 61000-3-2 standards on power quality requirements. Index Terms-Asymmetric, autoconfigured transformer, phase staggering, power quality indices, 20-pulse AC-DC converter. І. INTRODUCTION Use of AC-DC converter is indispensable in high power applications such as adjustable speed drives, high voltage DC transmission, electro-chemical processes, telecommunication power supplies, uninterruptible power supplies, induction heating, aircraft power supplies, and plasma power supplies. Which are fed from three-phase utility employing front-end diode bridge rectifiers possess a higher total harmonic distortion (THD), resulting in poor power factor, voltage distortion, overloading of capacitor bank, heating of equipment and other power quality problems. Modern AC-DC converters are expected to draw sinusoidal input current at unity power factor (PF) from the utility [1]. So, it is very essential to comply with the power quality standards set by IEEE-519 [2] and IEC 61000-3-2 [3] in such applications. One of the methods to reduce current harmonic distortion is to use phase shifting transformer (PST)-based multi-pulse AC-DC converters [4], [5]. Presently, the use of 6-pulse/12-pulse PST-based multipulse AC-DC converter in industrial applications exhibits poor power quality due to high THD and low PF. These PST-based multi-pulse AC-DC converters are of either isolated or nonisolated type with symmetric configuration. However, the requirement of higher magnetic arrangement and noncompliance with standard requirements, low PF are the
Three-Phase to Seven-Phase Power Converting Transformer
IEEE Transactions on Energy Conversion, 2012
Multiphase (more than three-phase electric power) electric drive system is the focus of a significant research in the last decade. Multiphase power transmission system is also investigated in the literature because multiphase transformers are needed at the input of rectifiers. In the multiphase power transmission and multiphase rectifier systems, the number of phases investigated is a multiple of three. However, the variable speed multiphase drive system considered in the literature are mostly of five, seven, nine, eleven, twelve, and fifteen phases. Such multiphase drive systems are invariably supplied from power electronic converters. In contrast, this paper proposes technique to obtain seven-phase output from three-phase supply system using special and novel transformer connections. Thus, with the proposed technique, a pure seven-phase sine-wave voltage/current is obtained, which can be used for motor testing purposes. In addition, a seven-phase power transmission and rectifier system may benefit from the proposed connection scheme. Complete design and testing of the proposed solution is presented. Analytical analysis, simulation, and experimental verifications are presented in the paper.
Hexagon-Connected Transformer-Based 20-Pulse AC–DC Converter for Power Quality Improvement
This paper presents the design and analysis of a hexagon connected transformer based 20-phase ac-dc converter which supplies direct torque controlled induction motor drives (DTCIMD's) in order to have better power quality conditions at the point of common coupling. The proposed converter output voltage is accomplished via two paralleled 10-pulse ac-dc converters each of them consisting of 5-phase diode bridge rectifier. A transformer is designed to supply the rectifiers. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The proposed structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for SCR > 20. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 8% for the proposed topology at variable loads.
Machines, 2021
Recently, the superiority of multi-phase systems in comparison to three-phase energy systems has been demonstrated with regards to power generation, transmission, distribution, and utilization in particular. Generally, two techniques, specifically semiconductor converter and special transformers (static and passive transformation) have been commonly employed for power generation by utilizing multi-phase systems from the available three-phase power system. The generation of multi-phase power at a fixed frequency by utilizing the static transformation method presents certain advantages compared to semiconductor converters such as reliability, cost-effectiveness, efficiency, and lower total harmonics distortion (THD). Multi-phase transformers are essential to evaluate the parameters of a multi-phase motor, as they require a multi-phase signal that is pure sine wave in nature. However, multi-phase transformers are not suitable for variable frequency applications. Moreover, they have sho...
Development of Three phase to five phase Transformer using a novel technique
2013
There is rapid development in the power system applications in early from the 19 century in many areas like transmission, distribution and power system appliances. In the year 1970 there is rapid development in the sector of machines. In late 1970 the first five phase induction motor drive system was proposed the world. Since there is huge research attempts has been placed to develop the multiphase drive systems. The three-phase supply is available from the grid; there is a need to develop a static phase transformation system to obtain a multiphase supply from the available three phase supply. So this paper suggests a novel transformer connection idea to convert the three phase grid supply to a five phase fixed voltage by maintaining the constant frequency supply. Now days the use of five phase motor dive is ever-increasing in commercial purpose and in future also. To satisfy these there are having solutions first, implementation of six phase transmission. To implement this we have ...