Micro-hydro power plants (MHPP) are usually built on mountains to provide electricity for rural communities. However, most of them are isolated from the national grid; thus, they require good control system to ensure the stability of both MHPP frequency and voltage outputs in spite of varying users load. This paper treats a new approach for frequency regulation of a MHPP against large load variations. For our simulation studies, a MHPP model is constructed from the mains physical equations that describe the nonlinear behavior of the plant. A self-tuning fuzzy proportional–integral (PI) controller, in which the controller gains are adjusted in real-time using a fuzzy logic inference system, is proposed. To demonstrate the effectiveness of the proposed controller, practical results under different loading conditions are presented. Those results show overall a good correlation between the computer simulation and the field-testing data.