A simplified wind farm simulation method for LVRT capability assessment

Wind turbines integrated into power grids are required by specific grid codes to withstand transitory low voltage during grid faults and generate reactive power in order to maintain the system stability, which is the so-called low voltage ride through (LVRT) capability. However, considering the effect of other electrical equipment in wind farms such as transformers and power lines, the LVRT capability of wind farm should be further assessed. Studies of cascading wind farm trip-off accidents also raise the demand of a feasible assessment method. This paper proposed a simplified wind farm simulation method for LVRT capability assessment, which aims to identify the severe scenarios in wind farm LVRT capability assessment through both theoretical and simulation methods in order to simplify the assessment procedure. Firstly, the basics of wind farm LVRT capability are shortly reviewed. Then two common-used assessment methods are discussed and compared as well. Based on the equivalent circuits for symmetrical and unsymmetrical cases, the simplification are implemented through theoretical analysis. In order to further narrow the scope of severe scenarios, the simulation model of a practical wind farm are developed. Over voltage and over current cases in dynamic simulation are studied, and the sensitivity analysis are used to determine different degrees of influences. Finally, conclusions in both theoretical and simulation studies are summarized and the recommended simulation scenarios for wind farm LVRT capability assessment are addressed.