Novel on-site LVRT testing method for full converter wind turbines

Abstract

Low Voltage Ride-through (LVRT) capability is now required for all large-scale Wind Turbines (WTs) connected to the grid. This thesis presents an on-site LVRT testing method for full-scale converter WTs. The new method makes use of the already installed WT converters to emulate the grid and produce a given fault for the WT under test. To guarantee the safety of the grid, both the WT under test and the grid emulating WTs are disconnected from the grid and operate in stand-alone mode during the test. The system configuration, testing procedure, control strategies are studied in this thesis. A wind farm with typical 2MW full converter Permanent Magnetic Synchronous Generator (PMSG) WTs was modelled and simulated. Practical issues including the minimum converter capability for grid emulation, WT over-speed limitation, grid impedance and fault conditions emulation were studied and discussed. Simulation results have shown that with only proper control algorithm modifications is it feasible to conduct on-site a series of LVRT tests for the full converter WT safely under the given grid capability and fault conditions.