Ripple Current Reduction in DC-Link Capacitor for a Single-Phase Two-Stage Inverter

The single-phase two-stage inverter is a common energy conversion unit for emerging decarbonization applications, like residential photovoltaics systems. Specifically, a dc-dc converter and an inverter are connected back-to-back with a dc-link capacitor serving as an energy buffer. The reliability of this unit depends on the lifespan of the dc-link capacitor, which decreases significantly with the rms value of the capacitor current. This paper proposes a simple but effective method to reduce the switching-frequency capacitor ripple current, which can extend the capacitor lifespan and increase the reliability of the energy conversion unit. The proposed method manipulates the switching pattern of the dc-dc converter by modifying its carrier waveform. Since the duty cycle is unaffected, the method is compatible with any existing carrier-based control scheme. Experimental results are obtained to verify the proposed method.