Design of Converter for Electric Vehicle Charging Application

Recent technological developments in the field of battery technology and fast charging favors electric transportation ecosystem. However, higher charging rates threaten reduced battery life cycles. Hence, level I charging systems for household application are extensively researched. Traditional LLC resonant converter is most attractive topology for on-board electric vehicle charging. Moreover, compounded charging characteristics of Li-ion battery demands broad output voltage and switching frequency variation. This, in turn, necessitates burst mode strategy for LLC converter during pre-charging recovery phase of a drained battery. Notwithstanding, burst mode strategy has many detrimental effects on the charging system and must be avoided. Therefore, this article proposes series-parallel LCLC resonant converter for electric vehicle charging. The presented converter provides a broad output voltage range and thus alleviates need for burst mode strategy when operated with synchronous pulse frequency modulation (PFM) and pulse width modulation (PWM). Experimentation results of 3 kW prototype confirm feasibility for intended electric vehicle charging application.