A novel 5-level hybrid rectifier using bypass concept for electric vehicle onboard battery charging

This paper presents a 5-level three-phase PFC rectifier, appropriate for electric vehicle (EV) onboard battery charging systems, with an innovative approach, named bypass concept. This function allows the converter to switch... [ view full abstract ]

This paper presents a 5-level three-phase PFC rectifier, appropriate for electric vehicle (EV) onboard battery charging systems, with an innovative approach, named bypass concept. This function allows the converter to switch between one of the available DC-links that best matches the required output levels depending on the operating point of the sinus wave, thus maximizing the efficiency. The 5-level operation allows the voltage steps to be lower than those found in three and two-level topologies, leading to a size reduction of the AC-inductors, lower harmonic contents and also reduction of common mode current and EMI. Furthermore, the voltage across the bypass switches is limited to the difference between the DC-link and the output voltages, enabling the use of semiconductors with lower voltage ratings, more efficient and less expensive. With this, both, conduction and switching losses can be reduced. The characteristics of the proposed system, including the principle of operation, modulation strategy, dimensioning equations and calculated losses, are described in detail. Finally, the feasibility of the bypass concept is demonstrated by means of a 22 kW hardware prototype.