Decentralised wide‐area fractional order damping controller for a large‐scale power system

Abstract

This study presents the design of wide-area fractional order damping controller for low frequency inter-area oscillations in Western Electricity Coordinating Council (WECC) system. The developed wide-area damping control scheme is implemented in a decentralised manner by examining the entire system through decentralised identification at the level of each generator bus and FACTS devices in large-scale system. The decentralised identification is done by applying n4sid (Subspace State Space System Identification) algorithm to the time-domain simulated response of WECC system. The main features of the proposed approach are: (a) measurement-based control which does not require complete model of WECC; (b) minimise the communicating signals required for damping controller and incorporate practical method of time-delay compensator (TDC) design to reduce the effect of time-varying delay. The performance of wide-area control (WAC) scheme is tested on the practical WECC system and verified by non-linear time-domain simulation. The proposed decentralised WAC scheme is compared with local and centralised control scheme, which enhances the damping of inter-area oscillation effectively compared to local control scheme and more reliable compared to centralised control scheme and its robustness is verified over a wide-range of operating conditions.