Design of a discrete Linear Quadratic Gaussian (DLQG) compensator for SSR damping using a sample invariant discrete model of TCSC

The paper presents the design of a discrete linear quadratic gaussian (DLQG) compensator for SSR damping which includes a full order Kalman filter to estimate all the states of the system and a full state feedback regulator. The controller is tested on IEEE First Benchmark model for SSR studies. A discrete linear-time invariant (LTI) model of a thyristor-controlled series capacitor (TCSC) in the synchronously rotating DQ reference frame is used in this system in which, the sample invariance is achieved by a simple transformation of the zero sequence variables in the discrete domain. This model of discrete TCSC is then integrated with discretised LTI model of the rest of the system under study. Thyristor firing is based on current synchronised phase-locked loop and the sampling frequency is six times the synchronous frequency. The eigen value analysis is done for this integrated system for different angles of conduction of the thyristor. The modeled system is having 27 state variables including the PLL states. The TCSC model and DLQG compensator design is validated using time domain simulation of the system.