Grid Fault Ride Through of a Medium-Voltage Three-Level Full Power Wind Power Converter

According to the fault ride through (FRT) demand to wind generation systems of grid codes, a control scheme of grid FRT under the whole grid change was proposed for a medium-voltage three-level full power wind power converter. This method coordinately controls the generator-side converter (MSC), the grid-side converter (GSC) and the chopper to: 1) reduce the unloading burden of the chopper by limiting the MSC output power during the low voltage ride through (LVRT), 2) insure the controllability of the GSC by adopting the self-adaptive control strategy of dc-link voltage and the carrier-based over-modulation strategy during the high voltage ride through (HVRT), 3) ensure the neutral-point potential (NPP) into the given threshold value by adopting the NP balancing control method based on zero-level elimination during the grid fault. The simulation results validate that the proposed method can fully use the controllability of MSC and GSC to ensure the smooth switching and safe operation, while decrease the unloading burden of the chopper. Thus, the FRT ability of full-scale three-level wind generation converters can be effectively improved.