International Journal of Power Electronics and Drive System (IJPEDS) Vol. 16, No. 3, September 2025, pp. 1775~1788 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v16.i3.pp1775-1788  1775 Journal homepage: http://ijpeds.iaescore.com A versatile three-level CLLC resonant converter for off-board EV chargers with wide voltage adaptability contribution Chandra Babu Guttikonda 1 , Pinni Srinivasa Varma 1 , Malligunta Kiran Kumar 1 , Kambhampati Venkata Govardhan Rao 2 , Rakesh Teerdala 2 , Santoshi Kanagala 3 1 Department of Electrical and Electronics Engineering, Koneru Lakshmaiah Education Foundation, Andhra Pradesh, India 2 Department of Electrical and Electronics Engineering, St. Martin’s Engineering College, Secunderabad, Telangana, India 3 Department of Engineering, University of Technology and Applied Sciences, Ibra, Sultanate of Oman Article Info ABSTRACT Article history: Received Jan 18, 2025 Revised May 13, 2025 Accepted May 25, 2025 The vehicle-to-grid (V2G) concept has gained significant attention in the last decade due to its potential to enhance direct current (DC) microgrid stability and reliability. Electric vehicles (EVs) play a central role in distributed energy storage systems, optimizing efficiency and enabling the integration of renewable energy sources. This study offers a unique three- level CLLC resonant converter developed for off-board EV chargers to promote bidirectional power transfer between DC microgrids and EVs. The suggested converter uses resonant CLLC components and two three-level full bridges to effectively handle a broad range of EV battery voltages (200 V–700 V). To ensure effective power conversion, the first harmonic approximation (FHA) model is used to analyse the converter's resonant frequency characteristics. The proposed system achieves high efficiency (>95%), with voltage stability maintained at 750 V under various load conditions. The converter's performance was validated through MATLAB- based simulations, comparing proportional integral (PI) and proportional integral derivative (PID) control strategies. The PID-controlled system demonstrated superior dynamic response, reduced current ripples, and enhanced voltage regulation compared to the PI-controlled system. This study demonstrates the viability of implementing a three-level CLLC resonant converter for efficient, bidirectional, and wide-voltage adaptation in EV charging infrastructure, thereby contributing to grid stability and renewable energy integration. Keywords: DC microgrid Electric vehicles Off-board EV charger Renewable energy integration Vehicle-to-grid This is an open access article under the CC BY-SA license. Corresponding Author: Kambhampati Venkata Govardhan Rao Department of Electrical and Electronics Engineering, St. Martin’s Engineering College Secunderabad, Telangana 500100, India Email: kv.govardhanrao@gmail.com 1. INTRODUCTION The increasing need for sustainable energy solutions, the widespread use of non-conventional energy sources, and the fast acceptance of electric vehicles (EVs) are all drastically altering the world's energy landscape [1], [2]. To accommodate this change, the electrical infrastructure must undergo improvements, such as the creation of more efficient grid systems and the introduction of technology that facilitates the interaction of customers, storage systems, and energy sources [3], [4]. The growing use of EVs and the incorporation of distributed energy resources (DERs) into direct current (DC) microgrids have highlighted the need for efficient bidirectional power converters that enable seamless vehicle-to-grid (V2G) and grid-to-vehicle (G2V) power transfer. Existing research has explored various converter topologies, such as LLC resonant converters, which