Modeling and Theoretical Investigation of Grid-Interactive Ultracapacitor Fuel-Cell for Renewable Application

This manuscript investigates the performance of an ultra-capacitor fuel cell in grid-connected mode. Voltage regulation to the ultra-capacitor was achieved with a three-level bidirectional DC-DC converter while achieving power flow from the grid to the ultra-capacitor via the bidirectional converter. The choice of a bidirectional three-level converter for voltage regulation is based on its inherently high efficiency, low harmonic profile, and compact size. Using the model equations of the converter and grid -connected inverter derived using the switching function approach, the grid's direct axis modulation index and quadrature axis modulation index, $M_{d}$ and $M_{q}$, respectively, were simulated in Matlab for both lagging and leading power factors. Moreover, the values of $M_{d}$ and $M_{q}$ were harnessed in a PLECS-based simulation of the proposed model to determine the effect of power factor correction on the current and power injection to the grid.