Single-stage charging rectifier based on a LLC resonant converter
Final Report Abstract
Today's on-board chargers of electric vehicles typically consist of two stages which are connected via a voltage DC link. A PFC rectifier is used as the first stage which ensures that the requirements for the mains current are met with respect to harmonic content and power factor. For the second converter stage, an LLC resonant converter has qualified in recent years which transmits the charging power to the traction battery in a galvanically isolated manner. The DC link consists of a bank of electrolytic capacitors in which the pulsating input power is buffered. The capacitors contribute a large portion of the charger’s volume and age rapidly, which is particularly undesirable for on-board chargers in electric vehicles. In the presented project, it is investigated whether this two-stage structure can be replaced by connecting the LLC resonant converter directly to the rectified line voltage. To use the LLC resonant converter as a single-stage charger, the circuit must be designed for a wide current and voltage range. For this purpose, an extended time-domain analysis was developed, whose high modeling accuracy is subsequently demonstrated experimentally. With the help of this time-domain analysis, the stress variables of the resonant converter are calculated in order to be able to make a preselection of the circuit parameters. Based on this, the optimization of the integrated transformer as a key component of the charger is carried out as well as its prototypical realization. In order to operate the designed single-stage charger on the public supply grid, a PFC control with high dynamics and robustness is required, for which conventional control approaches are not suitable. Therefore, a novel cascaded hysteresis control was designed for the LLC resonant converter which provides both the required dynamics and robustness against exemplar scattering. Finally, the achievable power density is determined by means of prototypes. Compared to established on-board chargers of today's electric vehicles, the single-stage approach increased the power density by about 53%.
Publications
-
Frequency- and Mode-Adaptive Control of DC-DC Converter for Efficency Improvement, PCIM Europe 2016; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2016, pp. 1-8
L. Keuck, F. Almai, S. Bolte, N. Froehleke and J. Böcker
-
A Comparative Study on Si-SJ-MOSFETs vs. GaN-HEMTs Used for LLC-Single-Stage Battery Charger, PCIM Europe 2017; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2017, pp. 1- 8
L. Keuck, P. Hosemann, B. Strothmann and J. Böcker
-
Adaptive Frequency Control of DC-DC-Converters for Maximum Efficiency Using Artificial Neural Network, PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2018, pp. 1- 8
L. Keuck, A. Munir, F. Schafmeister and J. Böcker
-
Switching Loss Characterization of Wide Band-Gap Devices by an Indirect Identification Methodology. In: Proc. 20th European Conference on Power Electronics and Applications (EPE-ECCE Europe). EPE; 2018:1-10
L. Keuck, N. Jabbar, F. Schafmeister, J. Böcker
-
Computer-Aided Design and Optimization of an Integrated Transformer with Distributed Air Gap and Leakage Path for an LLC Resonant Converter. 2019 IEEE Applied Power Electronics Conference and Exposition (APEC) (2019, 3), 1415-1422. American Geophysical Union (AGU).
Keuck, L.; Schafmeister, F. & Bocker, J.
-
Computer-Aided Design and Optimization of an Integrated Transformer with Distributed Air Gap and Leakage Path for LLC Resonant Converter, PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2019, pp. 1-8.
L. Keuck; F. Schafmeister; J. Böcker; H. Jungwirth & M. Schmidhuber
-
Robust Hysteresis Control for Full-Bridge LLC Resonant Converters Using an Isolated Measurement Scheme, PCIM Europe 2022; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2022, pp. 1-6.
L. Keuck; F. Schafmeister & J. Böcker
