Abstract
Owing to the increased emphasis on renewable resources, the development of suitable isolated power generators driven by energy sources such as wind, small hydro-electric, biogas, etc. has recently assumed greater significance. A capacitor self-excited induction generator has emerged as a suitable candidate of isolated power sources. The utilization of a three-phase squirrel cage induction motor as an autonomous self-excited induction generator is reviewed. Variations of electrical power due to changes in wind speed should be as small as possible. This is obtained by using an induction generator driven by a wind turbine. The system incorporates use of turbine blade angle pitch control to control the wind turbine speed and shaft torque. Variable pitch turbines operate efficiently over a wider range of wind speeds. Self excitation with capacitors at the stator terminals of the induction machines is well demonstrated experimentally on a d.c. motor-induction machine set. The parameters and the excitation requirements of the induction machine, run in self-excited induction generator mode, are determined. The effects of variations in prime mover speed, terminal capacitance and the load power factor on the machine terminal voltage are studied. A problem related to the fluctuation of power and frequency is the voltage regulation, this problem is mainly associated with wind turbines coupled to induction generators. Ways of overcoming the problem of voltage and frequency control in self-excited induction generators have been proposed in this work. The saturable reactors in parallel or series capacitors connected with the load are suggested for voltage regulation. The system frequency deviation due to random load perturbations is then reduced, using a superconducting magnetic energy storage unit connected to the system.
Published Version
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