A New Control Scheme for V2G Power Transfer in Modified Series-Parallel Resonant Converter

The dual active bridge (DAB) modified series-parallel resonant converter (MSPRC) is best suited for grid-to-vehicle (G2V) power transfer due to the narrow frequency range of operation, good short-circuit protection performance, and minimized circulating losses. For vehicle-to-grid (V2G) power transfer of MSPRC, efficiency is poor when the battery discharges to its lowest voltage. This paper proposes a new control scheme for V2G power transfer in MSPRC. The proposed constant power discharge frequency modulation scheme gives high conversion efficiency for V2G operation. The input voltage is maintained constant during the discharging operation for the wide variations in battery voltage. All the switches in the primary and secondary bridge of the proposed converter achieve soft switching. A three-level structure on the primary bridge allows the usage of low on-state resistance switches, thereby minimizing the switch conduction losses. The converter and its proposed control scheme are applicable for three-phase on-board battery chargers where the DC link voltage is very high. The experimental results from a 3.3-kW prototype validate the performance of the proposed control scheme.