Analysis of Sub-Synchronous Oscillation in Grid-Connected Wind Farm and Proposed Improved Solution

Sub-synchronous oscillation (SSO) is considered a stability issue related to turbine-generator systems, posing negative impacts on system integrity. The high penetration of wind energy has increased the urgency for this phenomenon. The analyses in this paper reveal that high compensation levels and low wind speeds are the two primary factors driving SSO, categorized as the induction generator effect (IGE), whereas the control parameters of the rotor-side converter (RSC) adversely contribute to the sub-synchronous control interaction (SSCI) phenomenon. Various solutions have been explored to suppress the SSO, which are divided into grid side and generation side approaches. However, relying on a single solution for either side does not provide the optimal damping effectiveness under critical operating conditions. Therefore, this paper proposes optimizing the internal control parameters of the RSC using meta-heuristic algorithms, including Particle Swarm Optimization (PSO), Cuckoo Search Algorithm (CSA), and Ant Colony Optimization (ACO). These tuned parameters are combined with a grid side solution based on a thyristor-controlled series capacitor (TCSC) or a generation side solution involving a supplementary damping controller (SDC) added to the RSC to improve SSO damping. This combination offers advantages such as low investment costs, simplicity, and high effectiveness. Both time-domain simulations and small-signal analyses have been carried out to demonstrate the capability of the improved approach, as they significantly enhance the damping ratio across low wind speed ranges and wide compensation levels. This study was conducted using MATLAB software based on the IEEE first benchmark, which was connected to the IEEE 14-bus system.