Frequency domain analysis of wind farm on the damping characteristics of a nearby synchronous generator

Abstract

Low‐frequency oscillations of a power system can be greatly affected by the fast growth of wind power due to the converter controls. It will result in a hidden danger to the small signal stability of the overall system if the mechanisms behind are not well understood. Therefore, this article aims to reveal the influence of the nonlinear control effects (e.g. phase‐locked loop, PLL) of the wind turbine on the electromechanical oscillations of a nearby synchronous generator (SG). To better perform the mechanistic analysis, a three‐machine study system that can properly reflect the interactions among the wind turbine, the SG, and the infinite bus is established. Then, the frequency domain model of such a system is developed, where the dominant dynamics of the wind turbine controls within the electromechanical time scale are modeled in detail. As a result, an equivalent power‐angle‐like frequency domain model is derived, from which the control effects of the wind turbine on the damping characteristic of the nearby SG can be intuitively revealed. It is shown that the wind turbine with the PV control mode can contribute more damping to the nearby SG than that with the PQ control mode. Moreover, the damping contribution is reduced with increasing bandwidth of controllers and the impact of PLL bandwidth on the SG damping can be negligible. All the mechanistic analyses are verified using time domain simulations in power systems computer aided design/electro magnetic transient in DC system (PSCAD/EMTDC), where a detailed system model is built. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.