Cascaded Multilevel Converter Applied to Fault Ride-Through Tests of Wind Turbines

Inhalt:
This paper describes the implementation of a 100kVA symmetrical cascaded multilevel converter used as a fault generator for fault ride-through tests of grid-connected wind turbines. The converter is able to emulate the main faults that usually occur in power systems, with no significant impact on the grid. The proposed system is comprised of two control levels: a central unit and local controllers in each power cell. Each power cell is composed of a back-to-back single-phase full-bridge converter, measurement circuits and a Digital Signal Processor (DSP) that controls the DC bus voltage through the grid-side converter and performs the modulation of the output-side converter. The central controller is a DSP that generates the voltage references for the cells and is responsible for the synchronization of all the cells to the central timer. Simulation results are shown to demonstrate the operation of the proposed converter.