Low-Frequency DC-Link Ripple Elimination in Power Converters With Reduced Capacitance by Multiresonant Direct Voltage Regulation

In this paper, a method for suppressing the low-frequency portion of dc-link ripple inevitably present in power conversion systems with reduced capacitance is proposed. The discussed active capacitance reduction circuitry (consisting of a feedback-controlled shunt-connected bidirectional buck-boost converter, terminated by a small auxiliary capacitance) directly regulates the dc-link voltage, utilizing a dual-loop control structure with parallel-connected multiresonant-bank-enhanced voltage loop stabilizing controller to achieve nearly constant, low-frequency-ripple-free steady-state dc-link voltage. Consequently, the proposed active capacitance reduction system may be perceived as a virtual infinite capacitor from the dc link point of view. The suggested circuitry is successfully applied to a single-phase commercial power factor correction front end in a nearly plug-and-play fashion. The control algorithm effectiveness is fully supported by simulations and experimental results.