Analysis and suppression of the input second harmonic current in two-stage inverter

The instantaneous output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency, generating second harmonic current (SHC) in the front-end dc-dc converter. Though reducing the SHC of the output filter inductor of the dc-dc converter (FIDC) can reduce the input SHC effectively, it depends on the capacitance of DC bus capacitor totally. In order to reduce the SHC of the input port more effectively, a control strategy is proposed in this paper, which extracts the SHC of the input port into the inductor current feedback path by a multiplier and a band-pass filter. The proposed control scheme can not only reduce the SHC significantly, but also is beneficial to improving the dynamic performance of the front-end dc-dc converter. Finally, a 1500-VA prototype is built, and the simulation results are presented to verify the effectiveness of the proposed control strategy.