A Family of Nonisolated Quadratic Buck-Boost Bidirectional Converters With Reduced Current Ripple for EV Charger Applications

Recently, onboard chargers with bidirectional power features have played a key role in minimizing energy imbalance at the grid for improved power system stability. This work proposes a new family of buck-boost bidirectional DC-DC converters inspired from the synchronously operated cascaded Ćuk converter topology. A comprehensive investigation of the operating theory and steady-state parameters of the proposed family of bidirectional converters highlights the features of wide voltage gain in both forward and backward modes. Furthermore, the continuous nature of currents at the input and output sides of the proposed converters enhances the battery's lifetime and reduces the size of the DC-link capacitor. Here, the proposed converters exhibit the same quadratic voltage gain with a common ground, but the voltage and current stress on the switches vary, providing flexibility to choose the suitable option for the charge applications of diverse EVs. A 300 W laboratory prototype of the proposed onboard EV charger is made, and real-time experimentations are performed to verify the theoretical findings and the nature of dynamic reference tracking. The proposed converters demonstrate promising performance, exhibiting a higher effective index, lower normalized voltage stress, lower current ripple, and impressive peak efficiencies.