Matching Analysis of LVRT Grid Code and Injection Current Dependent Voltage Response of WTC Connected to High Impedance AC Grid

With increasing penetration of wind power, wind turbines are usually required to stay connected and provide reactive current support according to LVRT (low voltage ride through) grid code during grid faults. However, for WTC (wind turbine converter) connected to high impedance AC grid, the voltage dependent current injection required by LVRT grid code may conflict with the injection current dependent voltage response of WTC, resulting in LVRT failure. In this letter, the matching of them is studied in detail. First, the voltage dependent current injection defined by LVRT grid code and injection current dependent voltage response of WTC are developed, respectively. Then the matching of them is revealed from the source-load matching analysis of equivalent circuit. It is identified that there exists constraints on the selection of K-factor to ensure the matching during low voltage grid faults. Simulated results are also presented to verify the analysis.