Improved subsynchronous oscillation detection method in a DFIG-based wind farm interfaced with a series-compensated network

Abstract

The use of series capacitors in long distance transmission lines leads to subsynchronous oscillation (SSO), which affects the stability and safety of power systems. The accurate detection of the SSO phenomenon within a short time is a necessary to avoid the harmful effects of SSO on power systems. This paper first presents an overview of previous SSO detection methods. An effective, secure, and improved SSO detection method based on the voltage signal is proposed and consists of two stages, namely, analysis and decision. In the analysis stage, the voltage magnitude signal passes through a first-order bandpass filter (fast filtration in the time domain) to only pass the subsynchronous frequency, and a new method for detecting the oscillation is added to avoid erroneous judgments and to make the method secure. In the decision stage, the best decision is taken (SSO detection, instant trip, or normal trip) based on the received data from the analysis stage. The robustness and speed of the improved SSO detection method are tested with the induction generator effect (IGE), subsynchronous control interaction (SSCI), and torsional interaction (TI). Simulation results indicate that the improved method can effectively and quickly detect the SSO phenomenon. The improved method is compared with the traditional method with different SSO types (IGE, TI, and SSCI) and is proven to be faster than the traditional method in all cases. In this study, the IEEE first benchmark model is adapted with a doubly fed induction generator (DFIG) wind farm to study the SSO phenomenon. MATLAB/SIMULINK software is used to validate the results.