Int. J. Power Electronics, Vol. 2, No. 4, 2010 389 Copyright © 2010 Inderscience Enterprises Ltd. A frequency control method for isolated photovoltaic-diesel hybrid power system without smoothing renewable power variations Manoj Datta*, Tomonobu Senjyu and Atsushi Yona University of the Ryukyus, 1 Senbaru Nishihara-cho Nakagami-gun, Okinawa 903-0213, Japan E-mail: k088659@eve.u-ryukyu.ac.jp E-mail: b985542@tec.u-ryukyu.ac.jp E-mail: yona@tec.u-ryukyu.ac.jp *Corresponding author Toshihisa Funabashi Meidensha Corporation, 2-1-1, Osaki, Shinagawa-Ku, Tokyo 141-6029, Japan E-mail: funabashi-t@mb.meidensha.co.jp Abstract: In this paper, a frequency control method is introduced for photovoltaic-diesel hybrid system by using a load estimator and an energy storage system. The proposed method is compared with an energy storage based conventional control method and with a fuzzy based frequency control method. Simulation results show that the proposed method is feasible to reduce the frequency deviations of the isolated power utility and delivers maximum power compared to both of the methods. Keywords: frequency control; hybrid power system; load estimator; energy storage system; ESS. Reference to this paper should be made as follows: Datta, M., Senjyu, T., Yona, A. and Funabashi, T. (2010) ‘A frequency control method for isolated photovoltaic-diesel hybrid power system without smoothing renewable power variations’, Int. J. Power Electronics, Vol. 2, No. 4, pp.389–411. Biographical notes: Manoj Datta received his BSc (first class with honours) in Electrical and Electronic Engineering from KUET (erstwhile BITK), Khulna, Bangladesh in 2002 and MSc in Electrical and Electronics Engineering from University of the Ryukyus, Okinawa, Japan in 2008. Currently, he is working toward his PhD degree at the University of the Ryukyus. Since 2003, he has been with the Department of Electrical and Electronic Engineering, KUET, Khulna, Bangladesh where he is an Assistant Professor. His research interests include photovoltaic system, power electronics, and motor drives. He was the recipient of the President’s Honorary Award for the year 2008 from the University of the Ryukyus. He is an Associate Member of the IEB, Bangladesh and student member of the IEICE, Japan, IEEJ, Japan and the IEEE Industrial Electronics Society and Power Engineering Society, USA.