Interleaved Pulse Width Modulation Based on Modified Carrier in Parallel Operation

An interleaved pulse width modulation (PWM) can be employed in a parallel operation of three-phase converters because the interleaved PWM increases the equivalent switching frequency and significantly enhances the output current harmonics. However, interleaved voltage pulse patterns provoke a huge circulating current, and a coupled inductor is employed to suppress the circulating current. Therefore, this study aims to improve the harmonics of voltage and current in parallel operation with a coupled inductor. For the aim, the harmonics of the interleaved PWM have been analyzed. Based on the analysis, a new PWM strategy has been devised by modifying the interleaved carrier. The proposed PWM improves the harmonics of voltage and current. However, unintended additional device switching occurs in the proposed method. Accordingly, a cost index (CI) is defined to show the improvement in the harmonics considering the additional device switching. The validity, feasibility, and effectiveness of the proposed method have been demonstrated by using CI. As a result, the computer simulation and experimental results show that the proposed PWM has efficiently improved the harmonics in various modulation indices.

Automated summary

The interleaved PWM can enhance the equivalent switching frequency and output current harmonics in parallel operation of three-phase converters. However, it may lead to circulating current, for which a coupled inductor is employed for suppression. A new PWM strategy has been devised to improve harmonics by modifying the interleaved carrier, although unintended additional device switching may occur.