Non-Isolated Fourth-Order Boost DC-DC Converter for Power Management in Low Voltage Low Power DC Grids: Design and Interaction Analysis

In this paper, a minimum-phase response fourth-order boost dc-dc converter (FBDC) exhibiting continuous input and output current is proposed. A voltage-mode controller is adopted to this converter to perform bus voltage regulation in a low voltage low power dc distribution system (LVPDS). FBDC supports additional load demand by interconnecting a second power source/battery. A systematic steady-state analysis for FBDC is established and the ripple content and other L-C design expressions are derived. The LVPDS is an integration of solar photovoltaic (PV) source using a conventional dc-dc boost converter (CBDC), and constant power load using a conventional dc-dc buck converter (CBuC). In this LVPDS, the FBDC primarily ensures dc bus voltage regulation, CBDC ensures the maximum power point tracking (MPPT) while CBuC regulates the load voltage. Various transfer function models, formulated through small-signal analysis, are used to address the controller design aspects and interconnected LVPDS stability issues. A generalized small-signal model of LVPDS is also developed to analyze the sub-system interactions arising during the coherent operation of BRC in this multi-converter system. The impact of connecting FBDC, as BRC, with other converters in the LVPDS is also analyzed. The laboratory prototype of a 48 V LVPDS is developed for experimental validation of bus voltage regulation and sub-system interactions. The theoretical and experimental results are found to be in close correlation with each other.