Comparative Evaluation of Modulation Schemes for Grid-connected Parallel Interleaved Inverters

A comparative evaluation of the different modulation schemes for the grid-connected converter with two parallel interleaved Voltage Source Converters (VSCs) is presented in this paper. The volume and the losses of the converter-side inductor of the LCL harmonic filter are evaluated for the grid-side converter of the multi-MW Wind Energy Conversion System (WECS). In order to achieve high current rating in MW-level WECS, two-level VSCs are often connected in parallel. The parallel connected VSCs can be operated with interleaved carrier signals and can be treated as a multi-level converter. As a result, the size of the harmonic filter components can be significantly reduced. However, circulating current flows between the parallel VSCs and it is often suppressed using a Coupled Inductor (CI). The losses and size of the CI are also evaluated for different modulation schemes and compared in this paper. A detailed discussion on the loss modeling of the inductive components and a multi-objective optimization method is also presented.