Adaptive Fuzzy Controller and Adaptive Self-Tuning Controller: Comparative Analysis for the Excitation Control of a Synchronous Generator IOAN FILIP, OCTAVIAN PROSTEAN, IOSIF SZEIDERT Department of Automation and Applied Informatics University “Politehnica” from Timisoara Bv. V.Parvan, no.2, Timisoara ROMANIA http://www.aut.utt.ro/~ifilip VALENTINA BALAS Department of Automatics Aurel Vlaicu University of Arad Bv. Revolutiei, no. 77, Arad ROMANIA GABRIELA PROSTEAN Department of Management University “Politehnica” from Timisoara Str. Remus, no.14, Timisoara ROMANIA Abstract: - This paper presents a comparative study between an adaptive fuzzy controller and an adaptive self- tuning controller with application to excitation control of a synchronous generator. The adaptive self-tuning controller is based on a dual action, obviously on control input, and also on reference signal. The proposed adaptive fuzzy controller includes a mechanism to adapt one of the tuning parameters. Some comparative studies are performed regarding the performance of a conventional fuzzy PI controller and the designed adaptive fuzzy PI controller (all with application to excitation control of a synchronous generator functioning in active power load regime). Also, to design the adaptive self-tuning controller two situations were considered concern the used parameters estimator: in the first case using a recursive least square error parameters estimator and, in the second, using a parameters estimator based on Givens orthogonal transformation. Key-Words: - fuzzy controller, adaptive self-tuning controller, identification, modeling and simulation, nonlinear systems, synchronous generator. 1 Introduction The synchronous generator represents the main equipment in major electric power systems. Due to its active role within the system - being used to supply electric power and to modify the voltage and the circulation of active and reactive power – the synchronous generator shows a capital significance for designers and engineers involved in solving system problems. The present conditions and future trends have determined the intensification of the concerns regarding the utilization of synchronous generator. [2] Also, in the last years there a trend of an increased interest occurs in the field of using the fuzzy logic in the area of embedded applications. The applicability domain of fuzzy logic is very large, including process control, system identification etc, and so the types of fuzzy controllers are continuously extended. The utilization of self-tuning controller and fuzzy controller has been applied in several industries. An application in power industry, where the adaptive property of these kinds of control strategies is an attractive feature, was considered. The power system is a complex dynamic system, in which the characteristics fluctuate with varying loads and varying generation schedules and the operating point changes too. The classical controllers (PI, PID) cannot maintain the same values of the quality indicators for all these perturbations. This is the reason that adaptive control (self-tuning or fuzzy), Proceedings of the 7th WSEAS International Conference on Automation & Information, Cavtat, Croatia, June 13-15, 2006 (pp89-94)