A Transformerless AC-AC Converter with Improved Power Quality Employed to Step-Down Power Frequency at Output

Naveed Ashraf; Ghulam Abbas; Nasim Ullah; Ahmad Aziz Al-Ahmadi; Abdul Rehman Yasin; Ahmed Bilal Awan; Mohsin Jamil

doi:10.3390/en15020667

Energies (Jan 2022)

A Transformerless AC-AC Converter with Improved Power Quality Employed to Step-Down Power Frequency at Output

Naveed Ashraf,
Ghulam Abbas,
Nasim Ullah,
Ahmad Aziz Al-Ahmadi,
Abdul Rehman Yasin,
Ahmed Bilal Awan,
Mohsin Jamil

Affiliations

Naveed Ashraf: Department of Electrical Engineering, The University of Lahore, Lahore 54000, Pakistan
Ghulam Abbas: Department of Electrical Engineering, The University of Lahore, Lahore 54000, Pakistan
Nasim Ullah: Department of Electrical Engineering, College of Engineering, Taif University, Taif 21944, Saudi Arabia
Ahmad Aziz Al-Ahmadi: Department of Electrical Engineering, College of Engineering, Taif University, Taif 21944, Saudi Arabia
Abdul Rehman Yasin: Department of Electrical Engineering, The University of Lahore, Lahore 54000, Pakistan
Ahmed Bilal Awan: Department of Electrical and Computer Engineering, College of Engineering and Information Technology, Ajman University, Ajman 346, United Arab Emirates
Mohsin Jamil: Department of Electrical and Computer Engineering, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada

DOI: https://doi.org/10.3390/en15020667
Journal volume & issue: Vol. 15, no. 2
p. 667

Abstract

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Variable voltage and frequency are required to govern the torque-speed characteristics of many industrial drive systems. Traditionally, this is achieved with a power converting system implemented with multistage converters. This technology is based on rectifying AC power into DC and then DC into AC with an inverter circuit. The power quality concerns of both conversion stages are tackled by selecting high switching frequency PWM control and harmonics mitigation filters. Also, using a bulky DC-link capacitor is one of the big sources of low system reliability, so this approach increases the conversion losses, circuit, and control complications. The frequency step-down conversion is very attractive with direct AC-AC converters as it has a simple control and circuit structure, but these converters face poor power quality challenges once the output frequency is decreased with respect to an input. In these converters, the total harmonic distortion (THD) of the output voltage becomes very poor once the output frequency is reduced. The problem of high THD of the output is addressed in the power converting circuits implemented with line frequency multi-winding transformers. The required number of output winding and switching devices (diodes and thyristors) increases once the value of the output frequency is decreased. This will increase the overall volume, cost, and losses. The use of a bulky and costly line frequency transformer may be eliminated if AC voltage controllers have non-inverted and inverted voltage buck capabilities, such existing topologies either have complex control schemes or require a large number of operating devices. Therefore, in this research article, a new transformerless frequency step-down converter employing fewer devices is proposed. This approach is realized with a high-frequency controlled rectifier for the required voltage stabilization and a low-frequency inverter bridge for frequency control. Its validation is supported by the results attained from Simulink and practical-based prototypes.

Published in Energies

ISSN: 1996-1073 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Technology
Website: http://www.mdpi.com/journal/energies

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