An Asymmetrical Split-Capacitor based Decoupling Control for a Single-Phase PFC Converter

This article proposes an asymmetrical split-capacitor (ASC) decoupling control strategy to achieve a constant DC output voltage against the output power fluctuations in a single-phase power factor correction (PFC) converter. The key objective is to absorb the ripple power using the decoupling circuit, consequently diminishing the need for large electrolytic capacitors (e-cap) at the DC-link, thereby improving the reliability and power density of the converter. Moreover, the proposed ASC decoupling control avoids additional energy storage components as the existing DC-link capacitors are utilised for the active power decoupling. Further, a variable factor accounting for the capacitance mismatch is devised and merged into the proposed control strategy to neutralize the impact of unbalanced decoupling capacitors arising due to lifetime degradation. Concurrently, a unity power factor is maintained at the input while ensuring that the input current's total harmonic distortion conforms to the prescribed thresholds stipulated by IEC61000-3-2 under both ideal and non-ideal input voltage scenarios. The effect of dissimilar capacitance analysis and its estimation presented is aimed at monitoring the split-capacitor health. Finally, a 1 kW laboratory prototype is developed and tested to demonstrate the circuit's viability for a wide input voltage range.