1. DESIGN & CONTROL SCHEME OF CLLC RESONANT DC-DC CONVERTERS
EE6149: Dissertation-Part-A Presentation by
ANIKET DATTATRAY PATIL
(Regd.No.: EE21114) (Roll No.: 21EEM1R04)
Under the Guidance of
DR. BHAGWAN KRISHNA MURTHY, Professor, EED, NITW
DEPARTMENT OF ELECTRICAL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY
(An Institution of National Importance, Ministry of Education, Govt. of India)
WARANGAL , INDIA

2. Contents INTRODUCTION MOTIVATION FOR SELECTION OF TOPIC
OBJECTIVES OF PROJECT
DESIGN REQUIREMENT
LITERATURE SURVEY
NEED OF CLLC RESONANT CONVERTER
OPERATION PRINCIPLE
SIMULATION
REFERENCE

3. INTRODUCTION
Numerous different bi-directional DC-DC converter topologies for EV chargers have been presented. Full-bridge voltage-source and current-source DC-DC converters are presented.
Since the converter operates in hard switching mode, active-clamped snubbers or passive-clamped snubbers are necessary to reduce switching loss and EMI. Although high efficiency is achieved over wide load conditions, the extra snubber circuit increases the size, volume and cost. proposes a symmetric full-bridge CLLC topology, featuring ZVS and ZCS in both the charging and the reverse discharging modes.
The transformer features a large turn ratio in order to cope with large difference between the input and output voltage, which makes it suitable for EV battery charging system. The transformer turns ratio can be easily adjusted to cope with different input/output voltage combinations.

4. MOTIVATION FOR SELECTION OF TOPIC
The main concern of this project is an on-board bidirectional charging system for electric vehicles that operates at high frequency and over wide battery voltage conditions.
The main aim is to enhance the DC-DC power conversion efficiency through extensive work in the following areas:
Analysis and development of the CLLC resonant topologies.
Control design.
Ripple current reduction.
Application of new converter topology.
Control technique for high efficiency operation.
Power loss evaluation.

5. Objective of Project
This thesis is about the DC-DC power conversion taking place in the EV charger. Primary objectives of this study are given here:
To understand the principle and operation of CLLC Resonant DC-DC Converters
To understand the concepts like soft-switching, primarily ZVS and ZCS, along with synchronous rectification and bidirectional power transfer.
To simulate the CLLC resonant converters in MATLAB Simulink and understand the variation in power transfer.
To design and develop a hardware for CLLC resonant converter to verify the simulation results.

6. Design Requirement
A typical bidirectional on-board battery charger usually employs two-stage topology including an frontend AC-DC converter stage connected to a DC-DC converter
The AC-DC converter acting as the front-end power factor corrector (PFC) stage rectifies the power from the grid to the battery load through the dc link capacitor followed by the DC-DC converter.
This Project work will mainly focus on the DC-DC converter part. And the priorities considered when designing the chargers are:
Safety(Galvanic Isolation)
Soft Switching
Power Density
High Efficiency
Bidirectional Power Flow

7. Design Requirement
Fig.1 Architecture for a traditional On-board EV Charger

8. TOPOLOGY CLASSIFICATIONS OF BIDIRECTIONAL DC-DC CONVERTERS
The bidirectional DC-DC converters can be classified into two main general groups of configurations, namely isolated and non-isolated topologies.

9. GENERAL CONTROL STRATEGIES USED IN NON-ISOLATED AND ISOLATED BIDIRECTIONAL DC-DC CONVERTERS
Picking a suitable control scheme for bidirectional converters depends on the topologies and the control problems that happen in real applications.

10. NEED OF CLLC RESONANT CONVERTER
Due to advantages like soft switching and high power density, LLC converters are frequently used for electric vehicle on-board and off-board chargers, but one significant drawback is that they are unidirectional in nature. The MOSFET bridge is used on the primary side, while the diode bridge is used on the secondary side of the resonant tank. Therefore, in the case of an LLC converter, G2V (Grid to Vehicle) charging is conceivable but V2G (Vehicle to Grid) charging is not.
The vehicles that can operate in a V2G network supply electricity to utility loads, acting as a source of distributed energy. Additionally, they aid in voltage and frequency regulation and utility load balancing. Moreover, when renewable energy sources like wind and solar generate extra power, these vehicles can consume it. These vehicles can also provide power during periods of heavy load demand.
The CLLC-resonant converter and DAB's configuration are identical. However, the latter design does have limitations, particularly short soft switching range under light load situations and power flow that is reliant on the transformer's leakage reactance value.

11. Fig. CLLC Converter Block Diagram
To overcome these limitations of LLC Converters and DAB Converters, the CLLC converters are used.To overcome these limitations of LLC Converters and DAB Converters, the CLLC converters are used.
In this topology, a diode bridge on the secondary side is replaced with an MOSFET bridge. Thus, due to the use of MOSFET—a bidirectional switching device—the CLLC converters are able to transfer the power from G2V and V2G both the sides. The block diagram of the CLLC converter is given in the Fig.
Fig. CLLC Converter Block Diagram

12. Operation Principle

13. Table:Typical operation of the switches and anti-parallel diodes in one switching cycle in Forward Mode
Table: Typical operation of the switches and anti-parallel diodes in one switching cycle in Reverse Mode

14. SIMULATION OF AC/DC BOOST PFC CONVERTER:

15. OUTPUT VOLTAGE WAVEFORM BOOST PFC:

16. INPUT VOLTAGE AND CURRENT OF BOOST PFC:

17. SIMULATION OF CLLC DC-DC CONVERTER

18. OUTPUT VOLTAGE WAVEFORM:
VOLTAGE RIPPLE: 123mV

19. References
[1] M. Yilmaz and P. T. Krein, “Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles,” IEEE transactions on Power Electronics, vol. 28, no. 5, pp , 2011.
[2] B. Singh, S. Singh and A. Chandra, “Comprehensive study of single-phase AC-DC power factor corrected converters with high-frequency isolation,” IEEE transactions on Industrial Electronics, vol. 4, pp , 2011.
[3] R. Kushwaha and B. Singh, “An improved power quality based PFC converter for EV battery charger,” in 2016 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES), 2016.
[4] P. He and A. Khaligh, “Design of 1 kW bidirectional half-bridge CLLC converter for electric vehicle charging systems,” in 2016 IEEE International Conference on Power Electronics, Drives, and Energy Systems, 2016.
[5] X. Liu, X. Wu, X. Li, X. Zhang, F. Deng and S. Sun, “A Synchronous Rectification Method of Bidirectional CLLC Resonant Converter Based on Phase and Duty Cycle Regulation,” in 47th Annual Conference of the IEEE Industrial Electronics Society, 2021

20. [6] S. Zou, J. Lu, A. Mallik and A. Khaligh, “3
[6] S. Zou, J. Lu, A. Mallik and A. Khaligh, “3.3kW CLLC converter with synchronous rectification for plug-in electric vehicles,” in 2017 IEEE Industry Applications Society Annual Meeting, 2017.
[7] U. Z. Zaka, “Design of Bidirectional DC–DC Resonant Converter for Vehicle-to-Grid Applications,” IEEE Transactions on Transportation Electrification, vol. 1, no. 3, p. 232, 2015.
[8] X. Liu, X. Wu, X. Li, X. Zhang, F. Deng and S. Sun, “A Synchronous Rectification Method of Bidirectional CLLC Resonant Converter Based on Phase and Duty Cycle Regulation,” in IECON th Annual Conference of the IEEE Industrial Electronics Society, 2021.

21. THANK-YOU