Parallel interleaved VSCs: Influence of the PWM scheme on the design of the coupled inductor

The line current ripple and the size of the dc-link capacitor can be reduced by interleaving the carriers of the parallel connected Voltage Source Converters (VSCs). However, the interleaving of the carriers gives rise to the circulating current between the VSCs, and it should be suppressed. To limit the circulating current, magnetic coupling between the interleaved legs of the corresponding phase is provided by means of a Coupled Inductor (CI). The design of the CI is strongly influenced by the Pulsewidth Modulation (PWM) scheme used. The analytical model to evaluate the flux-linkage in the CI is presented in this paper. The maximum flux density and the core losses, being the most important parameters for the CI design, are evaluated for continuous PWM and discontinuous pulsewidth modulation (DPWM) schemes. The effect of these PWM schemes on the design of the CI is discussed. The simulation and the experimental results are finally presented to validate the analysis.