Study on the Multiple Voltage Source Inverter for Grid-Connected Large-Scale Wind Energy Conversion System

This paper proposes a novel grid-connected multiple voltage source inverter (VSI) for large-scale wind energy conversion system (WECS) applications. Firstly, the typical configuration, operation principle and mathematical modeling of the direct-drive grid-connected WECS are analyzed in brief. Then, a suitable topology of the grid-connected multiple VSI composed of two six-pulse inverters, two separate zig-zag transformers and a dc-link capacitor is presented. In order to reduce numbers of commutations and to increase dc-link voltage utilization ratio of the proposed grid-connected multiple VSI, a quasi twelve-pulse phase-shift PAM switching strategy is demonstrated. Finally, a simulation test system is set up by using MATLAB/SIMULINK, and the results of simulation validate the effectiveness of the proposed grid-connected multiple VSI.