Control of Multi-cell AC/DC and Cascaded H-bridge DC/AC-basedAC/DC/AC Converter

Abstract

A single-phase two-stage AC/DC/AC converter topology is investigated in this paper, which involves multi-winding transformer-fed multi-cell AC/DC and cascaded H-bridge multi-level (CHBMLI) DC/AC converter stages. Both the converter stages utilize current control using the fixed and uniform switching methods, which simultaneously achieve the regulation of the DC link voltages of all the cells. The proposed control loop for the AC/DC converter stage uses a single-voltage sensor to control the DC link voltages of all the cells using self-voltage regulating property of the multi-winding transformer. This single-control loop uses the feedback of the instantaneous AC current at the primary of the transformer and any one of the DC link voltage to achieve the input AC current control and multiple DC link voltage control. The fixed frequency ramp comparison current control in AC/DC stage of the converter provides a uniform switching cycle among all the units. A phase-shifted multi-carrier PWM (PS-MCPWM)-based fixed frequency current control of the DC/AC converter comprising CHBMLI provides equal loading across all DC links of the AC/DC converter. The results are verified through PSCAD simulations and experimental results are obtained through the LabVIEW FPGA controller implemented for two-cell, five-level converter topology.

KEYWORDS:

• Cascaded H-bridge multi-level inverter (CHBMLI)
• Fixed switching frequency
• Multi-cell converter
• Multi-winding transformer

Additional information

Notes on contributors

Rajesh Gupta

Rajesh Gupta received the bachelor’s degree from the Madan Mohan Malviya Engineering College, Gorakhpur, India, in 1993, the master’s degree from the Birla Institute of Technology, Ranchi, India, in 1995, and the PhD degree from Indian Institute of Technology, Kanpur, India, in 2007, all in electrical engineering. He is currently a professor with the Department of Electrical Engineering, Motilal Nehru National Institute of Technology, Allahabad, India. His research interests include control of power electronics converters, multi-level converters, distribution system compensation and power conversion from renewable sources of energy. He is currently an in-charge of Electrical Machines Laboratory and heading student activity centre at his institute. He has undertaken various government projects from DST, SERB, CSIR and MNRE of India. He supervised 10 PhD and 50 Masters students.

Amit Kumar

Amit Kumar received the bachelor’s degree in electrical engineering from the Uttar Pradesh Technical University, India, in 2007, the master’s degree in electrical engineering with specialization in power electronics and ASIC design from Motilal Nehru National Institute of Technology Allahabad, India in 2010. He is working as electrical engineer since 2011 in Uttar Pradesh Power Corporation, India. Email: [email protected]