The multimodal non-identical generators having close frequency modes may complicate the design of subsynchronous damping controller. In this paper, the Band-Pass Filter (BPF) based Subsynchronous Damping Controller (SSDC) is designed with SSSC to damp multimode SSR. The system is adapted from IEEE First Benchmark Model (FBM) with two non-identical generators in parallel. One of the generators has a six-mass mechanical system and other has a four-mass mechanical system. The SSDC using reduced number of BPFs is proposed to enhance the damping of multimodal SSR while maintaining the frequency selectivity of filters. The proposed BPF based SSDC is designed to modulate the SSSC injected voltage so as to suppress the multimode components in the line. The DQ model is developed in MATLAB-Simulink using the differential and algebraic equations of the combined system. The analysis of SSR are carried out through damping torque, eigenvalue and transient simulation. The participation factor analysis is performed to identify the torsional modes of the generators. The eigenvalue analysis is used to select the number of BPFs. The BPFs with appropriate frequency selectivity are chosen to improve the damping of all critical torsional modes in the entire range of practical compensation level. The results show that, the peak negative damping at both generators is considerably reduced with the proposed SSDC in the entire range of torsional mode frequencies through practical compensation levels.

具有接近频率模式的多模态不同发电机可能使次同步阻尼控制器的设计复杂化。在本文中，基于带通滤波器（BPF）的次同步阻尼控制器（SSDC）设计与SSSC来阻尼多模SSR。该系统改编自 IEEE 第一基准模型 (FBM)，具有两个并联的不同发生器。其中一个发电机有一个六质量机械系统，另一个有一个四质量机械系统。提出了使用减少 BPF 数量的 SSDC 来增强多模态 SSR 的阻尼，同时保持滤波器的频率选择性。所提出的基于 BPF 的 SSDC 旨在调制 SSSC 注入电压，以抑制线路中的多模分量。DQ 模型是在 MATLAB-Simulink 中使用组合系统的微分和代数方程开发的。通过阻尼转矩、特征值和瞬态仿真对SSR进行分析。执行参与因子分析以识别发电机的扭转模式。特征值分析用于选择 BPF 的数量。选择具有适当频率选择性的 BPF 以改善整个实际补偿水平范围内所有关键扭转模式的阻尼。结果表明，通过实际补偿水平，在整个扭转模式频率范围内，所提出的 SSDC 显着降低了两个发电机的峰值负阻尼。执行参与因子分析以识别发电机的扭转模式。特征值分析用于选择 BPF 的数量。选择具有适当频率选择性的 BPF 以改善整个实际补偿水平范围内所有关键扭转模式的阻尼。结果表明，通过实际补偿水平，在整个扭转模式频率范围内，所提出的 SSDC 显着降低了两个发电机的峰值负阻尼。执行参与因子分析以识别发电机的扭转模式。特征值分析用于选择 BPF 的数量。选择具有适当频率选择性的 BPF 以改善整个实际补偿水平范围内所有关键扭转模式的阻尼。结果表明，通过实际补偿水平，在整个扭转模式频率范围内，所提出的 SSDC 显着降低了两个发电机的峰值负阻尼。