Impedance-Edited Multiple Low-Frequency Harmonic Current Adaptive Suppression

In the two-stage inverter, a large amount of low-frequency harmonic current will emerge in the front-end dc–dc converter and input dc voltage source. The low-frequency harmonic current will reduce the service life of the dc source and decrease the efficiency of the system. Additionally, the main components of low-frequency harmonic current fluctuate with uncertainty. To address those issues, an adaptive current suppression method based on impedance editing of the source-stage dc–dc converter is proposed in this article. Compared with the traditional active power filter (APF), the proposed adaptive low-frequency harmonic current suppression method does not require additional circuits, which will never decrease the system efficiency but reduce the cost. More importantly, when the amplitude of the main components of harmonic current fluctuates, adaptive multiple bandpass filters are proposed to adaptively suppress the main harmonic current, which never influences the dynamic performance. In addition, the virtual impedance is connected in parallel with the bus capacitor to reduce the bus voltage overshoot. The key parameters design of the proposed control strategy is given and the dynamic response of the proposed control strategy is also discussed. Finally, a prototype of 900 W was fabricated and tested.