Single-stage charging rectifier based on a LLC resonant converter

• Applicant: Professor Dr.-Ing. Joachim Böcker
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 394222435

Batteries are typically to be charged with DC-currents. That is why bulky electrolytic capacitors buffer the pulsing AC-line power of one-phase chargers. With one-stage conversion chargers, lifetime-limiting capacitors and a separate PFC stage can be avoided resulting in increased power density. However, a pulsing charge current must be tolerated, which does not harm batteries according to recent findings. Previous work on the LLC-topology ascertained promising results, but there are still open questions as follows: Optimising design at sinusoidal input voltage complying with PFC-standards by constraining the current conduction interval per half cycle and considering largely varying battery voltage depending on the state-of-charge by adapting the transformer turns ratio or a combination of both measures. Development and enhancement of a control concept evaluated so far only by simulations with respect to command action under constraints of component tolerances and operation point sensitivities by a commissioning-identification or an online-adaptation. Use of higher switching frequencies and reduction of reactive power required for zero-voltage switching by applying GaN-power devices in conjunction with an integrated transformer, which contains all inductive resonant components if effective, to achieve high efficiencies and power densities.

• DFG Programme: Research Grants