Fixed Low-Order Wide-Area Damping Controller Considering Time Delays and Power System Operation Uncertainties

This paper presents a procedure for the design of a Wide-Area Damping Controller (WADC) towards improving the low-frequency oscillation modes of the power system considering uncertainties in both nominal power system operation condition and time delay on the WADC communication channels. A set of possible operating conditions is linearized around their equilibrium points and used for the construction of the uncertainty model of the system. The lower and upper limits of the time delay are also included in the set. The WADC operation requires remote signals provided by Phasor Measurement Units and highly susceptible to failures or cyber-attacks that may compromise the controller performance. The proposed procedure evaluates in each stage if the resulting controller presents robustness to communication channel permanent failure. Modal analysis and time-domain nonlinear simulations were conducted in the IEEE 68-bus power system.

I. Introduction

Wide-Area Measurement Systems (WAMSs) monitor power systems through Phasor Measurement Units (PMUs) located in certain positions of the grid that acquire electrical measurements with synchronization provided by the Global Position System (GPS) [1]. The perspectives of applications of Wide-Area Measurements Systems for the monitoring, protection and control of the systems aroused have motivated their potential use in small-signal stability. Appropriately placed PMUs facilitate the observability of the power system dynamics and then one application is to use remote signals for a Wide-Area Damping Controller (WADC) to improve the damping of the low-frequency oscillations of the system [2].