# LLC DC-DC Converter Performances Improvement for Bidirectional Electric Vehicle Charger Application

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## Abstract

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## 1. Introduction

#### 1.1. Overview

#### 1.2. State of the Art

#### 1.3. Contributions

- Optimal design of LLC converter dimensions;
- EV charger cost and sizing minimization;
- Important improvement of the control frequency feasibility zone for V2X mode;
- Total reduction in the control frequency saturation zone for G2V mode;
- Control performances and converter efficiency improvement for EV bidirectional charger application with wide battery voltage and power variation.

## 2. Problem Statement

#### 2.1. G2V Mode

- The input voltage is presented as an ideal sinusoidal voltage source, which represents only the fundamental component ignoring all the higher-order harmonics;
- The output filter capacitor and the primary side leakage inductance of the transformer are ignored.

#### 2.2. V2X Mode

## 3. Proposed Optimization Strategy Design

#### 3.1. LLC Parameters Effect

#### 3.1.1. G2V Mode

- ${L}_{r}$ effect:With ${L}_{m}$ = ${L}_{m0}$, ${C}_{r}$ = ${C}_{r0}$, ${V}_{bat}$ = 420 V and by varying P (${P}_{min}<P<{P}_{max}$), ${f}_{0c}$ is presented in Figure 7 for different operating points with respect to the variation of ${L}_{r}$.It is clearly seen that ${f}_{0c}$ increases with the decrease in ${L}_{r}$.
- ${C}_{r}$ effect:With ${L}_{m}$ = ${L}_{m0}$, ${L}_{r}$ = ${L}_{r0}$, ${V}_{bat}$ = 420 V and by varying P, ${f}_{0c}$ is presented in Figure 8 for different operating points with respect to the variation of ${C}_{r}$.It is confirmed that ${f}_{0c}$ increases with the decrease in ${C}_{r}$ too, but at a lower rate than in the case of ${L}_{r}$.
- ${L}_{m}$ effect:With ${L}_{r}$ = ${L}_{r0}$, ${C}_{r}$ = ${C}_{r0}$, ${V}_{bat}$ = 420 V and by varying P, ${f}_{0c}$ is presented in Figure 9 for different operating points with respect to the variation of ${L}_{m}$.It is clearly seen that ${f}_{0c}$ increases with the decrease in ${L}_{m}$.

#### 3.1.2. V2X Mode

- ${L}_{r}$ effect:With ${C}_{r}$ = ${C}_{r0}$, ${V}_{bat}$ = 420 V and by varying P, ${f}_{0d}$ is presented in Figure 10 for different operating points with respect to the variation of ${L}_{r}$.It is clearly seen that ${f}_{0d}$ increases with the decrease in ${L}_{r}$.
- ${C}_{r}$ effect:With ${L}_{r}$ = ${L}_{r0}$, ${V}_{bat}$ = 420 V and by varying P, ${f}_{0d}$ is presented in Figure 11 for different operating points with respect to the variation of ${C}_{r}$.It is confirmed that ${f}_{0d}$ increases with the decrease in ${C}_{r}$ too.

#### 3.1.3. Summary

#### 3.2. Optimization Strategy Design

## 4. Simulations and Results

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Chen, H.; Qian, Z.; Zhang, R.; Zhang, Z.; Wu, J.; Ma, H.; He, X. Modular Four-Channel 50 kW WPT System With Decoupled Coil Design for Fast EV Charging. IEEE Access
**2021**, 9, 136083–136093. [Google Scholar] [CrossRef] - Chub, A.; Vinnikov, D.; Kosenko, R.; Liivik, E.; Galkin, I. Bidirectional DC–DC Converter for Modular Residential Battery Energy Storage Systems. IEEE Trans. Ind. Electron.
**2020**, 67, 1944–1955. [Google Scholar] [CrossRef] - Feng, W.; Yutao, L. Modelling of a Power Converter with Multiple Operating Modes. World Electr. Veh. J.
**2018**, 9, 7. [Google Scholar] [CrossRef] [Green Version] - Krismer, F.; Biela, J.; Kolar, J.W. A comparative evaluation of isolated bi-directional DC/DC converters with wide input and output voltage range. In Proceedings of the Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, Hong Kong, China, 2–6 October 2005; Volume 1, pp. 599–606. [Google Scholar] [CrossRef]
- Shah, S.S.; Iyer, V.M.; Bhattacharya, S. Exact Solution of ZVS Boundaries and AC-Port Currents in Dual Active Bridge Type DC–DC Converters. IEEE Trans. Power Electron.
**2019**, 34, 5043–5047. [Google Scholar] [CrossRef] - Li, X.; Bhat, A.K.S. Analysis and Design of High-Frequency Isolated Dual-Bridge Series Resonant DC/DC Converter. IEEE Trans. Power Electron.
**2010**, 25, 850–862. [Google Scholar] [CrossRef] - Yildiran, N. Design Methodology and Implementation of Half-Bridge LLC Resonant Converter. In Proceedings of the 2020 International Conference on Electrical, Communication, and Computer Engineering (ICECCE), Istanbul, Turkey, 12–13 June 2020; pp. 1–6. [Google Scholar] [CrossRef]
- Wei, Y.; Luo, Q.; Wang, Z.; Mantooth, H.A. A Complete Step-by-Step Optimal Design for LLC Resonant Converter. IEEE Trans. Power Electron.
**2021**, 36, 3674–3691. [Google Scholar] [CrossRef] - Hillers, A.; Christen, D.; Biela, J. Design of a Highly efficient bidirectional isolated LLC resonant converter. In Proceedings of the 2012 15th International Power Electronics and Motion Control Conference (EPE/PEMC), Novi Sad, Serbia, 4–6 September 2012; pp. 2–8. [Google Scholar] [CrossRef]
- Hsieh, G.C.; Tsai, C.Y.; Hsieh, S.H. Design Considerations for LLC Series-Resonant Converter in Two-Resonant Regions. In Proceedings of the 2007 IEEE Power Electronics Specialists Conference, Orlando, FL, USA, 17–21 June 2007; pp. 731–736. [Google Scholar] [CrossRef]
- Fang, Z.; Cai, T.; Duan, S.; Chen, C. Optimal Design Methodology for LLC Resonant Converter in Battery Charging Applications Based on Time-Weighted Average Efficiency. IEEE Trans. Power Electron.
**2015**, 30, 5469–5483. [Google Scholar] [CrossRef] - Beiranvand, R.; Rashidian, B.; Zolghadri, M.R.; Hossein Alavi, S.M. A Design Procedure for Optimizing the LLC Resonant Converter as a Wide Output Range Voltage Source. IEEE Trans. Power Electron.
**2012**, 27, 3749–3763. [Google Scholar] [CrossRef] - Liu, Z.; Du, J.; Yu, B. Design Method of Double-Boost DC/DC Converter with High Voltage Gain for Electric Vehicles. World Electr. Veh. J.
**2020**, 11, 64. [Google Scholar] [CrossRef] - Ahmadi, T.; Rokrok, E.; Hamzeh, M. Supervisory control of bipolar DC microgrids equipped with three-port multidirectional DC–DC converter for efficiency and system damping optimization. Sustain. Energy Grids Netw.
**2018**, 16, 327–340. [Google Scholar] [CrossRef] - Bi, K.; Liu, Y.; Zhu, Y.; Fan, Q. An impedance source modular DC/DC converter for energy storage system: Analysis and design. Int. J. Electr. Power Energy Syst.
**2021**, 133, 107261. [Google Scholar] [CrossRef] - Shi, R.; Li, S.; Zhang, P.; Lee, K.Y. Integration of renewable energy sources and electric vehicles in V2G network with adjustable robust optimization. Renew. Energy
**2020**, 153, 1067–1080. [Google Scholar] [CrossRef] - Dahmane, Y.; Chenouard, R.; Ghanes, M.; Alvarado-Ruiz, M. Optimized time step for electric vehicle charging optimization considering cost and temperature. Sustain. Energy Grids Netw.
**2021**, 26, 100468. [Google Scholar] [CrossRef] - Zorica, S.; Vukšić, M.; Betti, T. Design considerations of the multi-resonant converter as a constant current source for electrolyser utilisation. Int. J. Electr. Power Energy Syst.
**2019**, 111, 237–247. [Google Scholar] [CrossRef] - Matsushita, Y.; Noguchi, T.; Shimizu, K.; Taguchi, N.; Ishii, M. Control of Dual-Output DC/DC Converters Using Duty Cycle and Frequency. World Electr. Veh. J.
**2020**, 11, 72. [Google Scholar] [CrossRef] - Wei, Y.; Luo, Q.; Mantooth, A. LLC Resonant Converter Design Based on the Worst Operation Point. In Proceedings of the 2020 IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Dubrovnik, Croatia, 28 September–1 October 2020; pp. 219–224. [Google Scholar] [CrossRef]
- Liu, Y.C.; Chen, K.D.; Chen, C.; Syu, Y.L.; Lin, G.W.; Kim, K.A.; Chiu, H.J. Quarter-Turn Transformer Design and Optimization for High Power Density 1-MHz LLC Resonant Converter. IEEE Trans. Ind. Electron.
**2020**, 67, 1580–1591. [Google Scholar] [CrossRef] - Ho, G.K.Y.; Fang, Y.; Pong, B.M.H. A Multiphysics Design and Optimization Method for Air-Core Planar Transformers in High-Frequency LLC Resonant Converters. IEEE Trans. Ind. Electron.
**2020**, 67, 1605–1614. [Google Scholar] [CrossRef] - Ahmed, D.; Wang, L. Optimal Area-Product Model (OAPM) Based Non-Iterative Analytical Design Methodology for Litz-Wired High-Frequency Gapped- Transformer (LHFGT) in LLC Converters. IEEE Access
**2020**, 8, 18134–18148. [Google Scholar] [CrossRef] - Yu, R.; Ho, G.K.Y.; Pong, B.M.H.; Ling, B.W.K.; Lam, J. Computer-Aided Design and Optimization of High-Efficiency LLC Series Resonant Converter. IEEE Trans. Power Electron.
**2012**, 27, 3243–3256. [Google Scholar] [CrossRef] [Green Version] - Frivaldský, M.; Kandráč, J.; Špánik, P. Optimized design of the main circuit of LLC converter for high frequency application. In Proceedings of the 2010 International Conference on Applied Electronics, Pilsen, Czech Republic, 8–9 September 2010; pp. 1–4. [Google Scholar]
- Khoobroo, E.; Akhbari, M. Optimal design of LLC series resonant converter with enhanced controllability characteristic. In Proceedings of the 2012 3rd Power Electronics and Drive Systems Technology (PEDSTC), Tehran, Iran, 15–16 February 2012; pp. 392–396. [Google Scholar] [CrossRef]
- Al Attar, H.; Ghanes, M.; Hamida, M.; Taleb, M. Control strategies design and comparison of DC-DC LLC converter in V2X mode for electric vehicle charger application. In Proceedings of the 2021 IEEE Conference on Control Technology and Applications (CCTA), San Diego, CA, USA, 9–11 August 2021; p. 6. [Google Scholar]
- Ma, H.; Liu, Q.; Guo, J. A sliding-mode control scheme for llc resonant DC/DC converter with fast transient response. In Proceedings of the IECON 2012—38th Annual Conference on IEEE Industrial Electronics Society, Montreal, QC, Canada, 25–28 October 2012; pp. 162–167. [Google Scholar] [CrossRef]
- Yao, L.; Li, D.; Liu, L. An improved large signal model of full-bridge LLC converter. PLoS ONE
**2018**, 13, e0205904. [Google Scholar] [CrossRef] - Fang, Z.; Wang, J.; Duan, S.; Liu, K.; Cai, T. Control of an LLC Resonant Converter Using Load Feedback Linearization. IEEE Trans. Power Electron.
**2018**, 33, 887–898. [Google Scholar] [CrossRef] - Liu, C.; Liu, H.; Cai, G.; Cui, S.; Liu, H.; Yao, H. Novel Hybrid LLC Resonant and DAB Linear DC–DC Converter: Average Model and Experimental Verification. IEEE Trans. Ind. Electron.
**2017**, 64, 6970–6978. [Google Scholar] [CrossRef] - Zheng, K.; Zhang, G.; Zhou, D.; Li, J.; Yin, S. Modeling, Dynamic Analysis and Control Design of Full-Bridge LLC Resonant Converters with Sliding-Mode and PI Control Scheme. J. Power Electron.
**2018**, 18, 766–777. [Google Scholar] [CrossRef] - Mansour, A.; Hajer, M.; Faouzi, B.; Jamel, G. Analysis and Modeling of LLC Resonant Converter Used in Electric Vehicle. In Proceedings of the 2019 International Conference on Advanced Systems and Emergent Technologies (IC_ASET), Hammamet, Tunisia, 19–22 March 2019; pp. 357–362. [Google Scholar] [CrossRef]
- De Simone, S.; Adragna, C.; Spini, C.; Gattavari, G. Design-oriented steady-state analysis of LLC resonant converters based on FHA. In Proceedings of the International Symposium on Power Electronics, Electrical Drives, Automation and Motion, Taormina, Italy, 23–26 May 2006; pp. 200–207. [Google Scholar] [CrossRef]
- Taleb, M.; Maloum, A. Procédé de Commande en Fréquence de la Tension d’entrée d’un Convertisseur Courant Continu-Courant Continu. FR3083929A1, 17 January 2020. [Google Scholar]

LLC Parameters | ${\mathit{f}}_{\mathbf{0}\mathit{c}}$ | ${\mathit{f}}_{\mathbf{0}\mathit{d}}$ |
---|---|---|

${L}_{r}$ | Increase | High increase |

${C}_{r}$ | Increase | Very low increase |

${L}_{m}$ | Increase | None |

${V}_{min}$ | 240 V | ${V}_{max}$ | 430 V |

${P}_{min}$ | 1 kW | ${P}_{max}$ | 11 kW |

${C}_{r0}$ | 200 $\mathsf{\eta}$F | ${L}_{r0}$ | 20 $\mathsf{\mu}$H |

${L}_{m0}$ | 120 $\mathsf{\mu}$H | n | 1.6 |

${f}_{max}$ | 200 kHz | ${f}_{min}$ | 60 kHz |

${C}_{1}$ | 100 $\mathsf{\mu}$F | ${C}_{mosfet}$ | 0.75 $\mathsf{\eta}$F |

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**MDPI and ACS Style**

Al Attar, H.; Hamida, M.A.; Ghanes, M.; Taleb, M.
LLC DC-DC Converter Performances Improvement for Bidirectional Electric Vehicle Charger Application. *World Electr. Veh. J.* **2022**, *13*, 2.
https://doi.org/10.3390/wevj13010002

**AMA Style**

Al Attar H, Hamida MA, Ghanes M, Taleb M.
LLC DC-DC Converter Performances Improvement for Bidirectional Electric Vehicle Charger Application. *World Electric Vehicle Journal*. 2022; 13(1):2.
https://doi.org/10.3390/wevj13010002

**Chicago/Turabian Style**

Al Attar, Houssein, Mohamed Assaad Hamida, Malek Ghanes, and Miassa Taleb.
2022. "LLC DC-DC Converter Performances Improvement for Bidirectional Electric Vehicle Charger Application" *World Electric Vehicle Journal* 13, no. 1: 2.
https://doi.org/10.3390/wevj13010002