Control and Lifetime Assessment of a Bidirectional EV Charger with Reactive Power Support

This paper investigates the impact of reactive power support on the reliability of a bidirectional electric vehicle (EV) charger operating as a grid support asset. A 50 kW charger composed of a three phase VSI rectifier, an isolated dual active bridge converter, and a bidirectional DC-DC stage is considered. A reactive power control strategy is implemented to provide voltage support during grid voltage sags while maintaining battery charging operation under a CC--CV profile. The proposed control system is validated through simulations and experimental tests performed on the grid-side converter. In addition, a reliability assessment is carried out for the VSI IGBTs and DC-link capacitors using electrothermal modeling, lifetime models, Rainflow cycle counting, and Monte Carlo analysis. The results show that reactive power injection contributes to voltage support during sag events but increases the thermal stress imposed on the power semiconductors. For the investigated mission profiles, the provision of reactive power support significantly reduces the lifetime of the IGBT modules, whereas the impact on the DC-link capacitors remains limited. The presented results highlight the trade-off between ancillary service provision and converter lifetime, providing useful insights for the design and operation of bidirectional EV charging infrastructure.