Robust PWMSC Damping Controller Tuning on the Augmented Lagrangian PSO Algorithm

The paper introduces a new flexible alternating current transmission systems (FACTS) controller based on pulse width modulated series compensator (PWMSC) for damping inter-area oscillations in power systems. The PWMSC can modulate the impedance of a transmission line through the variation of the duty cycle of AC link. The main purpose of this work is to verify the capability of the PWMSC to mitigate low frequency oscillations. For this reason, a novel current injection model of PWMSC is proposed and incorporated in the system model. This study proposes a novel tuning strategy for robust PWMSC damping controller based on the augmented Lagrangian particle swarm optimization (ALPSO) satisfying the multiple H_∞ performance criteria. Proposed method does not need any conservative assumption unlike the conventional techniques, and often enables us to find the desired parameters of controller just by solving the constrained optimization problem in a straightforward way. In the paper, a verification of the designed controller by means of digital simulations of single machine and four-machine power systems is presented. The net results show that the proposed controller improves the stability of both test systems significantly in a number of fault cases at different levels of power flow in tie-line.