Design of Coupling Robust Damping Controller for AC-DC Interconnection System

The robust control method is effective in suppressing the phenomenon of low frequency oscillations (LFOs) in power systems. Aiming at the problem of LFOs in AC/DC transmission system, a coupling robust damping controller design method based on multiple input multiple output (MIMO) system model is proposed to enhance the damping of specific oscillation modes by utilizing the interaction between different control loops instead of decoupling the control loops. Firstly, the global least squares—rotation invariant (TLS-ESPRIT) technique is used to identify the reduced order model of MIMO system and the oscillation modes of the system. Then a kind of hybrid H2/H∞ method is used to design coupling robust damping controller based on different control loops. The balanced truncation method is used to reduce the order of the controller, which has both robust performance and practical engineering application. Finally, a four-machine two-area AC/DC test system is built in PSCAD/EMTDC. The time domain simulation results show that the coupling robust controller can effectively suppress the LFOs under various disturbances and faults, and the system can quickly recover stable operation. At the same time, output feedback control is utilized, which is convenient for engineering practice.