A Novel Multi-Functional Observer Based Distributed WADC for Large Power System Using Modified Decoupled Control Approach

Feeble damping of inter-area oscillations presents a consequential threat to modern power systems, leading to power swings, voltage fluctuations, and potential system instability, which could result in blackouts. To tackle this issue, this article introduces a novel Multi-Functional Observer (MFO) based Wide-Area Damping Controller (WADC) design. The WADC gain and selection of feedback signals are determined using the Modified Decoupled Control (MDC) approach. As the direct input signals to the WADC are not available through phasor measurement units (PMUs), the study utilizes MFOs to estimate the chosen feedback signals based on PMU data. These estimated feedback signals are used as supplementary inputs to the High-Voltage Direct Current (HVDC) tie-line converter and exciter of selected machines to enhance system stability in a distributed manner. The proposed approach is rigorously tested and validated on a complex 25-machine, 105-bus practical system, which represents a truncated model of India's Eastern Regional (ER) Grid. Furthermore, Non-linear simulation results indicate that the proposed WADC algorithm effectively dampens multiple inter-area modes while leaving other modes almost unaffected. The proposed MFO-based WADC adopted Interacting Multiple Model (IMM) strategy to validate robust damping performance for large uncertainties in operating points.