Distributed load control of autonomous renewable energy systems

Autonomous renewable energy systems such as wind, solar, and micro-hydro require control methods to maintain stability, due to the real time variation of input energy and load, while maximizing the use of renewable energy. This paper describes the application of load control using a novel frequency and voltage-sensing device. The device uses a low cost microcontroller to monitor the system frequency and voltage. Load switching is carried out based on this information. Software was developed for frequency and voltage measurements and tested on a 18 kW, single phase, 50 Hz, micro-hydro system. A fuzzy control system was then developed which makes intelligent load switching decisions using inputs from the measurement algorithms coupled with expert knowledge expressed in the form of control rules. This load control system was then tested on the same micro-hydro system and on a site powered by a 60 kW, 3 phase, 50 Hz wind turbine only.