No abstract

This paper proposes a simple and passive harmonic reduction method at dc link of 20-pulse rectifier. The 20-pulse topology is obtained via two paralleled 10-pulse ac–dc converters, each of them consisting of a five-phase (five-leg) diode bridge rectifier. For independent operation of the paralleled diode-bridge rectifiers, a zero sequence blocking transformer (ZSBT) is designed and implemented. Connection of a tapped inter-phase transformer (IPT) at the output of the ZSBT results in doubling the number of the output voltage pulses. The application of the pulse doubling technique with a low power rating (2% of the load power rating) results in a simpler and more economical configuration of the whole system and increased number of pulses. The design is suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The proposed structure is simulated using Matlab/Simulink software under different loading conditions. The simulation results confirm the significant improvement of the power quality indices (IEEE-519 standard requirements) at the point of common coupling (PCC). Experimental results are obtained using the designed and constructed laboratory prototype of the proposed converter to validate the design procedure and the simulation results. The VA rating of the magnetic circuit is calculated to confirm the savings in space, volume, weight and cost of the proposed configuration.

No abstract

No abstract

In this paper, a new multi-pulse clean power converter topology is presented with lower than 3% input current total harmonic distortion (THD). The topology is based on the combination of a 36-pulse converter and a pulse doubling circuit. The 36-pulse converter consists of a "polygon" autotransformer and two 18-pulse diode bridge rectifiers. Pulse doubling circuit consists of zerosequence-blocking transformer (ZSBT) and tapped interphase transformer (IPT). The important advantage of the proposed AC-DC converter is considerable reduction in burdens of the magnetic parts with respect to the nominal load rating. It provides more economical solution to achieve harmonic mitigation in electric power systems as compared with other 72-pulse AC-DC converters. The simulation and experimental results show that the input current THD is less than 3% using the proposed topology. The results indicate a significant reduction in the total cost and volume of the proposed 72-pulse configuration in comparison with similar configurations. Also, it is shown that the proposed converter rating is about 44% of the DC load power.

No abstract

This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMDs) 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 acdc converters each of them consisting of three-phase diode bridge rectifiers. 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 6-pulse, 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.

To increase the power rating and reduce the cost and complexity of a multi-pulse rectifier (MPR), 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 relatively simple structure and low weight. However, 12-pulse rectifiers cannot technically meet the standards of harmonic distortion requirements for some industrial applications, and therefore they must be used along with output filters. Two cost-effective 24-pulse rectifiers (24PRs) are suggested in the article, which consist of a polygon autotransformer 12PR and two pulse doubling circuits (PDCs) at dc link. The first PDC (PDC1) is based on an interphase transformer (IPT) with a step-up secondary winding, and the second one (PDC2) is based on an IPT with a step-down secondary winding. To show the advantages of the proposed combinations compared with other solutions, simulation results are used, and also a prototype is implemented to evaluate and verify the simulation results. The simulation and experimental test results show that the total harmonic distortion (%THD) of the input current for the 12PR with PDC1 is less than 3.67%, and the 12PR with PDC2 is less than 1.45%, which meets the IEEE 519 and DO-160G requirements. Also, it is shown that in comparison with other solutions, the proposed two configurations are cost-effective, power factor is near unity, rating is almost 29% of the load rating, and the efficiency is almost 97.5%, which makes them a practical solution for more electric aircraft.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.