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Due to high penetration of renewable energy sources, inter-area oscillations (IAOs) have become serious concern for power system stability. Hence, a wide-area damping controller (WADC) strategy is proposed for thyristor-controlled series compensator (TCSC) device to effectively damp IAOs. The feedback signals for the WADC design are selected by the modal sparse linear quadratic regulator (MSLQR) method, which are sole signals that modulate simple gains to achieve the desired damping performance. Moreover, the multi-model framework approach is adopted to ensure optimal damping corresponding to any uncertainties such as changing operating scenarios and time latency in feedback signals. However, the proposed primary control does not provide frequency regulation; hence, a secondary control based on the switched integral controller is applied in addition to primary damping control to further maintain the frequency at the steady-state level. Performance of suggested strategy is evaluated and verified on IEEE 4-machine, 11-bus system and 16-machine, 68-bus system. A comprehensive analysis shows significant improvement in the damping performance of concerned modes, leaving the local modes almost unaffected while maintaining the frequency at the prescribed steady-state level.

The intermittent nature of Wind Turbine Systems (WTSs) can severely affect the Low-Frequency Oscillations (LFOs) in the power system. Hence, a Wide-Area Damping Controller (WADC) is designed in this paper to provide adequate damping to critical LFO modes. This WADC utilizes a modal-based prescribed degree approach, ensuring the specified shift of concerned modes from their existing position. However, the design of WADC at a fixed operating point and time delay in feedback signals does not provide robust performance as these uncertainties may vary for different time intervals. Specifically, time-varying delays should be tackled appropriately, or the system's damping performance will be severely hampered. Keeping this in view, an Interacting Multiple Model (IMM) infrastructure is employed to provide robust damping performance for such uncertainties. The IMM strategy utilizes the deviation of output error between actual and probable plants, through which weights are assigned to corresponding probable WADCs via the Bayesian framework. The simulations are performed on the nonlinear 4-machine, 11-bus system and the complex 16-machine, 68-bus system using MATLAB/Simulink platform. The results demonstrate that the proposed IMM-based WADC furnishes adequate damping to critical LFO modes for operating point and time delay uncertainties.

Low-frequency oscillations (LFOs) are one of the major concerns in modern power system; hence, these should be appropriately treated in order to achieve reliable operation. In this regard, we propose a novel wide-area damping controller (WADC) to dampen LFO modes effectively. The proposed WADC utilized thyristor controlled series compensator (TCSC) based flexible ac transmission system (FACTS) device through which supplementary input is provided. The selection of modal feedback signals for WADC design is carried out using coordinated modal transformation and linear quadratic regulator (LQR) approach. However, these signals are not accessible directly through the phasor measurement devices (PMDs). Hence, this paper utilizes a reduced-order functional observer to estimate the feedback signals using PMD data. The estimated feedback signals are further modulated by simple gains to improve the damping of critical LFO modes. The proposed methodology is validated on benchmark 4-machine 11-bus system and a more practical 25-machine, 105-bus system representing the complex Eastern Regional Grid (ERG) of India. The results obtained on these nonlinear systems show a significant improvement in damping of the critical LFOs leaving the other modes almost unaffected.