PROJECT TITLE:

Frequency-Adaptive Filtering of Low-Frequency Harmonic Current in Fuel Cell Power Conditioning Systems - 2015

ABSTRACT:

Based on one of the most researched multiinput dc-dc converter topologies for renewable energy systems, the multi-input twin-active bridge (DAB) dc-dc converter, the effectiveness of harmonic current absorption by the energy storage branch in fuel cell power conditioning systems is critically evaluated. The closed-loop output impedances of the converter below single-voltage-loop and dual-loop controls are derived and compared. It's shown that both control ways can effectively cut back the converter's closed-loop output impedance, so favoring the flow of harmonic current and stop it from being drawn from either the fuel cell branch or the dc-link capacitor. However, as shown by experimental results, the utilization of standard PI control alone still produces noticeable voltage ripple on the dc voltage bus due to harmonic current being drawn from the dc-link capacitor. Proportional-resonant control is proposed to effectively complete the dc-bus voltage variation by generating an extraordinarily low impedance path for harmonic current flow at specific frequency. An analog-based frequency tracking circuit is more proposed to adjust the resonant frequency for compensating the result of harmonic frequency variation.