The multimodal non-identical generators having close frequency modes may complicate the design of Subsynchronous Damping Controller (SSDC). In this paper, we propose a multimodal SSDC using Kalman Filter (KF) to damp Subsynchronous Resonance (SSR). The proposed SSDC is incorporated with Static Synchronous Series Capacitor (SSSC). The system is adapted from the 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 KF based SSDC is designed to adjust the SSSC injected voltage as to suppress the subsynchronous currents flow to generators. The parameters of KF based SSDC are selected to enrich the torsional modes of both generators. The results show that the peak negative damping viewed at both generators is substantially reduced with proposed KF based SSDC and mitigate SSR. © 2020, World Academy of Research in Science and Engineering. All rights reserved.