Performance analysis and calculation of critical inductance and output voltage ripple of a simple non-isolated multi-input bidirectional DC-DC converter

In this paper, a simple non-isolated multiple input (MI) bidirectional DC-DC topology is proposed which can operate in buck, boost, or buck-boost modes. The proposed topology utilizes a battery pack to realize the bidirectional power flow operation especially when the input sources are non-storable ones. The excess energy of input sources can be stored in the battery and be injected to the load, when required. Simultaneous or independent power transfer of input sources is also provided. For better evaluation, the proposed topology has been compared with several recently presented novel topologies, from view point of number of inductors, capacitors, switches, and diodes. Comparison results show that the proposed topology utilizes less number of components (switches, inductors, capacitors, and current sensors) which can reduce the size, cost, and complexity of converter. Different operational modes of the proposed topology (unidirectional buck, boost, buck-boost modes, and bidirectional mode) have been presented. Also, boost mode of the proposed topology has been investigated in detail, from design point of view, and generalized relationships have been proposed for calculation of critical inductance (CI) and output voltage ripple (OVR) of proposed n-input boost topology. To validate proposed theoretical concepts, the proposed topology has been modeled and simulated in PSCAD/EMTDC software, and the 3-input boost version has been experimentally implemented. Simulation and experimental results confirm appropriate performance of the proposed topology.