Application of Fuzzy Logic (FL) theory to self-tuning PID controller for the reactive power compensation using Synchronous Machine (SM) is investigated in this paper. The measured Power Factor (PF) is adjusted to a required value using FGS based PID controller. If the measured PF is different from the required reference value an error signal is generated. This error signal and change of error are evaluated by FLC to obtain the new constants values for the PID controller that used to drive six-pulse full wave thyristorized rectifier circuit, which can thus control the excitation field voltage. A VAR compensation for the weak bus, with a desired PF, has been applied on the modified IEEE-5 bus sample systems using bifurcation analysis and Q-V sensitivity methods as voltage stability indicator. In this paper, a suitable model of the SM has been presented. Loading and no load conditions in addition to excitation field voltage have been tested. A good agreement between practical and theoretical results has been observed.
Simulation results demonstrate that better control performance can be achieved in comparison with Ziegler-Nichols controllers and Kitamori's PID controllers. It has been found that the proposed controller (FGS based PID) provides fast response, flexible, nonlinear gain characteristic and adaptive operation. It is concluded that the reactive power compensation system with a FGS based PID controller of SM is reliable, sensitive, economical, faster, and more efficient with no harmonics.
Keywords: Reactive Power Compensation, PID controller, Fuzzy Logic, Fuzzy Gain Scheduling, Voltage Stability, Bifurcation, and Matlab-Simulink.