Abstract: The objective of this paper is to improve the stability of power system by using fuzzy based PID controller. It will be capable in providing the proper damping to generator oscillation, which will reduce the effect of instability. Here the application of the fuzzy PID controller how much effective to stabilize the power system in comparison to fuzzy logic -based power system stabilizer has been discussed. Here Speed deviation (ds) and acceleration (da) of the rotor synchronous generator has been taken as inputs of the proposed model. The excitation control of fuzzy PID based power system has been done by the tuning process, i.e. by tuning the acceleration and speed of the rotor synchronous generator. A good damping characteristic over a wide range has been obtained by the system inputs i.e. speed deviation and acceleration of synchronous machine to stabilizer. Now the power systems are interconnected which results low frequency oscillations. The disturbances or the low frequency (LFO) can be mitigated by providing a supplementary damping signal which is produced from the system membership function, which is typically depending on the acceleration and speed of the rotor synchronous generator. How the proposed fuzzy-PID controller-based power system stabilizer is superior to fuzzy logic-based stabilizer, has been discussed and shown in the simulation results Keywords: PID, PI, FLC, LFO, PSS, AVRs I. INTRODUCTION To maintain the state of equilibrium ,the power system stability has the tendency of the power system to develop restoring forces which can be equal to or greater than the disturbing forces[1]. In the power system the generation of electricity has been completely relied on the synchronous machines, all the machines on power system has to satisfy a necessary condition I.e. all the synchronous machine has to remain in synchronism. The dynamic relationship between the generator roto angles and power angles has the key aspects to maintain the stability. Hence as it shows the dynamic behavior, so it is a dynamic system. Today the electric power system has no longer operated as isolated system, it has been operated as interconnected systems which includes millions of electrical elements and also spreads over large geographical regions in worldwide [2-3]. The main work of the thesis is to make the power system stable with as much less time as we can. The power system should be reliable and economical for generation, transmission and distribution. To prepare a better system than the exciting one the survey of the previous work is important. From where one can gate enormous idea to enhance the work. II.PROBLEM IDENTIFICATION For better result or for the cause of reliability of power supply power systems are interred connected. Which results a low frequencies oscillation in the poser system. This is due to the frequent variation of the load demand. In the power system the goal for maximum power transfer and power system security can be obtained those low frequency oscillation (LFOs)which has been also related to the small singnal stability of a power system. The stability problem will be disregarded when it has been found the satisfactory solution of using damper windings on the generator rotors and the turbines can control those oscillations. A major cause of system instability is weak synchronizing torque among the generators which is obtained when power systems began to operate closer to their stability limits. The steady-state stability of the power systems has been improved by the help of automatic voltage regulators (AVR). To develop a large interconnected power system, a major concern is to transfer the large amounts of power with less losses in the long transmission lines[4-5]. To reduce the inhibiting effects of LFOs a supplementary controller has been introduced in the control loop such as the conventional power system stabilizers (CPSSs)to the AVRs on the generators .It has been observed that the CPSSs work quit perfectly at the particular network configuration and also in the steady state conditions for which they has been meant to Improvement of Power System Stability by using FLC based PID Controller Smitanjali Rout, Satish Dhar Dr. Abhinna Chandra Biswal Department of Electrical and Electronics Engineering Centurion University of Technology and Management Odisha, India Journal of Xidian University VOLUME 14, ISSUE 5, 2020 ISSN No:1001-2400 http://xadzkjdx.cn/ https://doi.org/10.37896/jxu14.5/101 956