Enhanced Phase-Shifted PWM Carrier Disposition for Interleaved Voltage-Source Inverters

This letter presents a novel implementation of pulse width modulation that improves the quality of the line-to-line output voltages in interleaved multiphase voltage-source inverters (VSIs). In multiphase VSIs with n interleaved parallel-connected legs, the best single-phase output voltage is achieved when the carriers are evenly phase shifted. However, switching among nonadjacent levels can be observed at regular intervals in the line-to-line voltages, causing bad harmonic performance. With the proposed method, switching in the line-to-line voltages happens exclusively between adjacent levels. The modulator utilizes two sets of n evenly phase-shifted carriers that are dynamically allocated. Because of its generality, the proposed implementation is valid for any number of phases and any number of legs in parallel. A MATLAB/Simulink model has been set up for simulation purposes. Selected experimental results obtained from a three-phase VSI made up with two and three legs in parallel per phase are reported, confirming the enhancement attained with the proposed implementation.