24 PULSE AC-DC CONVERTERS FOR IMPROVED POWER QUALITY (original) (raw)
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Design and Analysis of 24-PULSE Ac-DC Converter
2015
This paper proposes a non-isolated 24-pulse controlled AC-DC convereter for medium power rating derives. The proposed AC-DC converter configuration consists of a polygon auto transformer to overcome current harmonic problems in AC mains. It improves power quality at AC mains and it meets IEEE-519 standard requirements at varying loads. A set of power quality indices on input AC mains and on DC buses for a load fed from 6-pulse and 12-pulse AC-DC converters is also given to compare their performance. The proposed 24-pulse AC-DC converter is found capable of suppressing up to the 21 st harmonics in the supply current along with the power-factor improvement close to unity in the wide operating range of the drive. It involves pulse multiplication in a 12-pulse AC-DC converter. It is observed that input current total harmonic distortion (THD) of less than 8% is possible with the proposed topology of AC-DC converter at varying loads.
Power-Quality improvement by multi pulse AC–DC converters for Varying Loads
2011
The present work is an endeavor towards analyzing the different multi-pulse converters in solving the harmonic problem in a three-phase converter system. The effect of increasing the number of pulses on the performance of AC to DC converters is analyzed.This paper presents the design and analysis of a novel 30-pulse ac–dc converter for harmonic mitigation under varying loads. The proposed multi pulse( 30-pulse) ac-dc converter is based on a polygon-connected autotransformer with reduced magnetics.The proposed ac–dc converter is able to eliminate lower than29th order harmonics in the ac supply current. Auto transformer is modified The resulting supply current is near sinusoidal in shape with low total harmonic distortion and a nearly unity power factor. Moreover, the design of an to make it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. To validate the proposed approach, various power-quality indices are presented under varying loads. Th...
This is a well-known fact that during a transformerrectifier combination undesirable harmonic line currents may be generated. The rectification of alternating current power to direct current power itself may produce undesirable current harmonics. The non-linear loads cause the severe current harmonics that can not be tolerated. These harmonic currents can cause either a shutdown of the device or the unacceptable powering of the devices. The non-isolated multi-pulse converters and the Multi-pulse converters in general can be applied to achieve the clean power which is of major priority in higher power rating applications. Generally, by increasing the number of pulses in a multi-pulse converter THD (total harmonic distortion) can be reduced up to the allowable limits. Thepresentwork istoanalyses the differentmulti-pulse AC toDC (18-pulse, 24-pulse, 36-pulse, and 48-pules) converters insolvingthe harmonic problem in athree-phase converter system. The effect of increasing the number of pulses on the performance of ac-dc converters is analyzed. THD is the major factor considered for the performance comparison of various converters.
MULTI-PULSE AC-DC CONVERTERS FOR POWER QUALITY IMPROVEMENT IN DC DRIVES
This article presents the design, modeling and simulation of three-phase multi-pulseAC–DC converters (MPC)for the improvement of power quality by the elimination of harmonics in ac mains and ripples in dc output.Multi pulse converters are operated with DC motors and run at different conditions to obtain output with less harmonic distortion.Total harmonic distortion is calculated by FFT analysis.With the help of MATLAB/Simulink modelling, simulation and digital implementation has been done for power quality improvement in DC drives using multi pulse converters. In converter circuits generally semiconductor switching devises are used which generates harmonics voltages and currents. Three phase ac-dc conversion of electric power are employed in the applications such as Adjustable speed drives (ASDs), Highvoltage dc (HVDC) transmission, Electro-chemical processes such as electroplating, Telecommunicationpower supplies, batterycharging, uninterruptible power supplies (UPS), High-capacitymagnet power supplies, high-power induction heatingequipment'sand converters for renewable energy conversion systems The major contributor to power system harmonics and consequences are diode bridge rectifiers. Generally converters are fed from three phase ac supply and have power quality problems like harmonics injection causes ac voltage distortion, rippled dc voltages and poor power factor. Various methods are used to minimize the problems in ac-dc converters. The DC motor drives are used in industries for converting electrical energy to mechanical energy. The advantage of choosing DC motors over AC components is because of their speed control.The main objective of the paper is to provide the power to consumer/industry load with proper sinusoidal wave of the voltage and current with fixed frequency and magnitude with minimized Total harmonic distortion,according to IEEE standards THD must be less than 5%. Power quality improvement can be achieved in 3-phase ac-dc converters by using multi-pulse converters. The converters are strong, simple, rough and efficient. The auto transformer based arrangement are more economical due to reduced magnetic losses. Different configurations from 12 pulse, controlled 24 pulse and controlled 48 pulse based ac-dc converters have been reported in literature.In literature several publications are reviewed and found on reduction on total harmonic distortion of power systems which are discussed in below section 2. This paper is divided into five sections. Starting with Section 1 gives introduction. Section gives detailed view of literature on reducing THD. Section 3 discussed about modeling of uncontrolled 12 pulseand controlled 12 pulse converter, controlled 24 pulse converter, controlled 48 pulse converter. Section 4 presents digital implementation, THD results and discussion. Section 5 concludes this paper. II. LITERATURE REVIEW The main objective of the research is to lessen harmonics in converters. Many methods are implemented and developed by the researches based on the needs and suitability. Selective harmonic elimination with pulse width modulation(SHEPWM) or programmed-PWM. This method calculates the switching instants of the devices in order to satisfy certain criteria. SHE method gives best outputs among PWM methods with low switching frequency to fundamental frequency ratios, direct control over output waveform harmonics.
Power Quality Improvement by Multi Pulse Converter for DC Motor
This paper present the simulation of 24-pulse AC-DC converter is designed, modeled, simulate and develop to feed DC motor as a load. The proposed AC-DC converter configuration consists of phase shifting zigzag transformer to overcome current harmonic problem in AC mains. It improves power quality at AC mains, Ripple voltage at DC sides. It meets IEEE-519 standard requirements for DC motor load. Designs of different phase shifting 6, 12, 18 and 24 pulse converter have been presented along with their MATLAB based simulation. The effect of increasing the number of pulses on the performance of AC to DC converters is analyzed for performance comparison the major factor consider is the total harmonic distortion (THD), Ripple voltage
2012 3rd Power Electronics and Drive Systems Technology (PEDSTC), 2012
This paper presents a pulse doubling technique in a 36-pulse ac-dc converter which supplies direct torque-controlled motor drives (DTCIMD's) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 36-pulse rectified output voltage is accomplished via two paralleled eighteen-pulse ac-dc converters each of them consisting of nine-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. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 72 pulses. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse, 36-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 3% for the proposed topology at variable loads.
Technical and economical comparison of different autotransformer based 36 pulse AC-DC Converters
2020
Three-phase multipulse ac–dc converters (MPC) are being developed to improve power quality to reduce harmonics in ac mains and ripples in dc output. This study, based on technical and economic factors, compares different autotransformer based 36 pulse AC-DC Converters. This paper presents a comparison of tapped delta, polygon and T connected autotransformer based 36-pulse AC-DC converters. These converters were implemented and simulations were made using Matlab/Simulink software for similar ratings under different load conditions. A set of power quality indices on input ac mains and on a dc bus for a DTCIMD fed from different 36-pulse ac-dc converters is given to compare their performance. The economic comparison of 36 pulse ac–dc converters is based on the apparent power (kVA) ratings of the different autotransformers for 36 pulse AC-DC converters. Also, a prototype is developed and the experimental measurements obtained are presented to validate the feasibility and operability of ...
Journal of Applied Research and Technology
Three-phase multipulse AC-DC converters (MPC) are developed for improving power quality to reduce harmonics in ac mains and ripples in dc output. This study, based on technical and economic factors, compares different autotransformer-based 30-pulse AC-DC converters. In this paper, the comparison of two topologies of autotransformer-based 30-pulse AC-DC converter has been presented. In topology A, three-phase AC voltages are given to the autotransformer, which produces five sets of three-phase voltage and, in topology B, three-phase AC voltages are given to the autotransformer, which produces three sets of five-phase voltages of same magnitude and distributed in time through phase shifts of 12 •. Topology A included polygon, hexagon, star, fork, and T-connected autotransformer-based 30-pulse AC-DC converters, and topology B Included polygon, and T-connected autotransformer-based 30-pulse AC-DC converters. These converters have been implemented and simulation using Matlab/Simulink software for similar ratings under different load conditions has been performed. A set of power-quality indices on input ac mains and on a dc bus for a DTCIMD fed from different 30-pulse AC-DC converters is given to compare their performance. Economic comparison of 30 pulse AC-DC converters is based on the apparent power (kVA) ratings of the different autotransformer for 30 pulse AC-DC converters.
A 28-pulse AC–DC converter for line current harmonic reduction
IET Power Electronics, 2008
A novel transformer for 28-pulse AC-DC converter configuration is designed, modelled and simulated to feed isolated DC varying loads. The proposed transformer is suitable for large current rating rectifiers such as electric-aircraft power supply, electro-winning, electro-chemical processes, induction heating, plasma torches and so on, where isolation is required mainly for stepping down the supply voltage. It consists of two paralleled 14-pulse AC-DC converters involving seven-phase shifted AC fed diode bridges. It improves power quality at AC mains and it meets power quality IEEE-519 standards requirements at varying loads.
This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMD's) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 12-pulse rectified output voltage is accomplished via two paralleled six-pulse ac-dc converters each of them consisting of three-phase diode bridge rectifier. An autotransformer 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. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 24 pulses. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6pulse, 12-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 5% for the proposed topology at various loads.