Analysis and mitigation of SSR in non-identical generators using multimodal BPF based SSDC.

Area of Science:

• Electrical Engineering
• Power Systems Analysis
• Control Systems

Background:

• Multimodal subsynchronous resonance (SSR) poses challenges in power systems with non-identical generators due to closely spaced frequency modes.
• Designing effective subsynchronous damping controllers (SSDC) for such complex systems requires careful consideration of frequency selectivity and damping performance.

Purpose of the Study:

• To design and evaluate a Band-Pass Filter (BPF) based Subsynchronous Damping Controller (SSDC) for a two-generator system experiencing multimodal SSR.
• To enhance the damping of multimodal SSR by modulating the Static Synchronous Series Compensator (SSSC) injected voltage using a reduced number of BPFs.

Main Methods:

• The IEEE First Benchmark Model (FBM) with two non-identical generators (one with a six-mass and one with a four-mass mechanical system) was adapted.
• A DQ model was developed in MATLAB-Simulink for system analysis.
• Subsynchronous resonance analysis was performed using damping torque, eigenvalue analysis, and transient simulations.
• Participation factor analysis identified generator torsional modes, and eigenvalue analysis guided the selection of BPFs.

Main Results:

• The proposed BPF-based SSDC effectively suppressed multimode SSR components by modulating the SSSC injected voltage.
• Eigenvalue analysis confirmed improved damping for all critical torsional modes across practical compensation levels.
• Transient simulations demonstrated a significant reduction in peak negative damping at both generators.

Conclusions:

• The developed BPF-based SSDC provides enhanced damping for multimodal SSR in complex power systems.
• The controller maintains frequency selectivity while effectively mitigating SSR across a wide range of operating conditions.
• This approach offers a viable solution for improving power system stability in the presence of subsynchronous oscillations.