A Single Phase Self-Excited Induction Generator with Voltage and Frequency Regulation for use in a Remote Area Power Supply

Micro-hydro generator schemes are an attractive choice for electricity generation in remote locations or underdeveloped communities where a grid supply is not available. Since such systems must be low cost, reliable, and robust to minimise maintenance requirements, the use of a standard squirrel cage induction motor is appealing – either three phase or single phase depending on power ratings and availability. The principles of generation using induction motors are well established, and self generation is readily achieved by connecting excitation capacitors in parallel with the motor, to form a resonant LC circuit. However, control of the output voltage and frequency is not possible if fixed excitation capacitors are used. This paper presents a method of controlling a self-exciting single phase induction motor, where the shunt capacitance connected across the machine is varied to regulate the output voltage magnitude, while the output frequency is regulated by using a triac to vary the power fed to a resistive dump load. The paper reviews self excitation principles for a single phase induction motor, develops the voltage and frequency regulation concepts, presents the design of the microprocessor based regulation system, and then concludes with experimental results that verify the system’s operation.