A Modular Bidirectional Topology for Grid-Tied PV Powered EV Chargers with Isolated Single-Stage Sub-Modules

Renewable energy sources (RES) such as solar photovoltaic (PV) are employed in electric vehicle (EV) charging stations to promote sustainable transportation and reduce the load on the AC grid. This paper introduces a modular power converter topology that interfaces with solar PV, EV batteries, and the AC grid. The proposed topology supports EV battery charging in two modes: DC/DC (from PV modules) and AC/DC (from the AC grid). Additionally, during peak hours, EV batteries can function as energy storage units (ESUs) in vehicle-to-grid (V2G) mode. A central element of the proposed topology is the submodule (SM), which is implemented as a single-stage isolated bidirectional Cuk-based converter. This converter is chosen for its exceptional features, including high efficiency and inherent power factor correction (PFC) due to continuous input and output currents. The paper first details the operating modes of the Cuk-based SM. To improve performance, an extra switching state is added in the AC/DC (rectifier) mode, enabling the second-order harmonic from the AC grid to be stored within the Cuk SM instead of being passed to the battery. Additionally, power losses at the SM level are examined, and the effectiveness of the proposed topology is demonstrated through experimental results.