Proposing FOPID-based PSS2B Stabilizer Using MGSO to Improve Damping of Electromechanical Oscillations in a Multi-machine Power System

Proposing novel power system stabilizers (PSSs) to damp effectively low frequency oscillations (LFOs) in multimachine power systems is an interesting topic which has attracted many attentions in recent years. Fractional order controllers (FOCs) have found new applications in power system stability issues, recently. In current paper, fractional order proportional integral derivative (FOPID) controller is employed in design of a practical stabilizer, which is based on integral of accelerating power. The authors have proposed an FOPID-based PSS2B stabilizer to improve the damping of LFOs in a multimachine power system. The design of FOPID-PSS2B is formulated as a nonlinear optimization problem in which adjustable parameters are optimized simultaneously via a modified group search optimization (MGSO) algorithm by minimizing integral of time multiplied squared error (ITSE) performance index. The damping performance of the proposed stabilizer is compared with the earlier stabilizers of PID-PSS2B and FOPID-PSS. The results of time domain simulations on a 3-machine 6-bus test system in MATLAB/Simulink environment reveal that the proposed FOPID-PSS2B achieves superior damping performance in comparison with the former stabilizers. Besides, sensitivity analysis is carried out to evaluate the robustness of the proposed stabilizer. FOMCON toolbox is used for fractional order modeling and control.