Isolated generation in micro hydroeletric power plant (MHPP) through the induction generator (IG) has been the subject of extensive research due to the fact that this type of electrical machine is easy to operate, requires simplified maintenance, and has also a lower cost when compared to the synchronous machine, mainly in the range from 0.5 to 50 kW. In this work a single voltage control loop of an squirrel cage induction generator in an isolated operation system was implemented in a 30 kW MHPP. The proposed system uses a ballast load (BL) controlled via a digital circuit board. The generated voltage and frequency are maintained around their nominal rated values for typical applications in rural areas. For this purpose a control system has been implemented via phase anti–parallel thyristors. Tests were made with varying loads to obtain the voltage waveforms in the main load (ML) and BL. The control allowed by the electronic board was also tested for performance under sudden connection and disconnection of loads. The proposed system proved to be robust and effective in controlling the voltage and frequency of the isolated system.