A generalized control scheme derivation approach for front-end DC-DC converters in two-stage inverters

The instantaneous output power of the two-stage single-phase inverter pulsates at twice the output voltage frequency, resulting in the second harmonic current (SHC) in the input voltage source and the front-end dc-dc converter. To keep the input voltage source and the front-end dc-dc converter free from the negative effects brought by SHC, special considerations shall be taken on the control scheme of the front-end dc-dc converter. In this paper, a generalized control scheme derivation approach, which bases on the small-signal ac equivalent circuit model with virtual series impedance and parallel impedance, is proposed for different types of front-end dc-dc converters applied in different occasions. By adopting different forms of series impedance and parallel impedance, various control schemes for buck-derived, boost-derived and buck-boost-derived front-end dc-dc converters are obtained. Finally, the feasibility of these control schemes is verified by simulation results.