Coordinated tuning of PSS and TCSC to improve Hopf Bifurcation margin in multimachine power system by a modified Bacteria Foraging Algorithm

• First, the Voltage Stability Limit (VSL) of the system is improved by optimized allocation of PV-bus voltage, OLTC and TCSC.
• The controllers of PSS and TCSC are tuned to improve the loadability limit of power system, before Hopf Bifurcation.
• For the purpose of optimization modified of Bacteria Foraging Algorithm (BFA) is utilized.
• Instead of focusing on merits of BFA over other algorithms, a suitable objective function is designed.
• The PSS and TCSC controllers tuned at optimized settings with proper choice of objective function improve VSL before HB.

Recent research works have reported the effects of rotor angle dynamics of generators on bifurcation related system instability. This study intends to verify the possible influence of the Power System Stabilizers (PSS) and the Thyristor Controlled Series Capacitors (TCSC), on instabilities related to the Hopf Bifurcation (HB). Recently proposed optimization algorithm known as Bacteria Foraging Algorithm (BFA) in its modified version is applied in this study to tune the controller parameters of nine numbers of PSS and two numbers of TCSC present in the 10 machine New England power system. The main objective of this work is to maximize the margin of loading in the same system before the occurrence of the HB. Moreover, the formulation of a properly designed objective function is also an important issue that affects the final result. The objective function, that is formulated only to improve the overall damping in power system, may not be sufficient to avoid the HB under stressed operating condition. Therefore, this study proposes to reformulate an eigenvalue based objective function to improve the extent of loading before the HB could occur in the system. A coordinated control of the TCSC with those of the PSS may enable the controllers to delay the point of HB, compared to the case when the PSS alone were operating in the system. At the outset, the control parameter settings of several transformer taps and PV-bus voltages of nine generators were optimized to improve the steady state Voltage Stability Limit (VSL) of the system. At these settings, the damping controller parameters are tuned to improve the loadability before the point of HB. Similar approach is adopted when the TCSCs were operating coordinately with the PSS. At the end, small perturbation cases were simulated in the system to verify the performance of designed controllers in time domain analysis. The results further establish the efficacy of the controllers