Utilizing Harmonic Injection to Reduce Energy Storage and Required Capacitance in an Active Series-Stacked Energy Buffer for Single-Phase Systems

Single-phase grid-connected converters typically re-quire reactive buffering on the dc bus to maintain a constant de power in the presence of ac-side twice-line-frequency power pulsation. Compared to bulky passive capacitors, active buffers can process higher amounts of power with reduced capacitance requirements. This paper investigates a method for energy storage reduction in the capacitors of the series-stacked buffer (SSB) utilizing deliberate ac-side current harmonic injections within IEC61000-3-2 regulatory limits. This work outlines the theory behind harmonic injection in the active buffer, demon-strates a digital control implementation, and provides hardware verification showing that appropriately injected harmonics can be used to reduce the energy stored and thus the capacitance required in each SSB capacitor.