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One of the main disadvantage of the squirrel cage self-excited induction generator is the variation of both voltage and frequency with the speed variations. The amplitude and frequency of the output voltage of a self-excited induction generator may be adjusted across a wide speed range by using a slip-ring induction machine. In this, paper a study on using a self-excited slip-ring induction generator (SEWRIG) to generate an output with constant voltage and frequency by controlling effective rotor resistance. The steady state characteristics are obtained by analyzing the normalized equivalent circuit of the self-excited induction generator. The study revealed that, for a given stator load impedance, as the speed is varied both the frequency and the voltage can be maintained constant, without changing the excitation capacitance. A closed-loop control scheme for the constant voltage and frequency operation of (SEWRIG) using chopper-controlled rotor resistance is also discussed. With a properly tuned proportional-plusintegral (PI) controller using Particle Swarm Optimization (PSO) algorithm, satisfactory dynamic performance of the (SEWRIG) is obtained. Experiments performed on a 370 W laboratory machine to confirm the feasibility of the proposed method.

This paper presents a simple and accurate approach to compute the capacitance requirements for the self-excitation process in three-phase isolated induction generators. The method proposed in this paper is based on the nodal analysis of the generalized equivalent circuit commonly used in the analysis of the induction generators. The proposed method involves simple algebraic equations and only one equation is solved iteratively to determine the capacitance requirements for the self-excitation process in induction generators. Simple computer algorithms are developed to predict the minimum value of capacitance for all loading conditions. The computer simulations obtained using the proposed method are compared with those obtained by solving the sixth order polynomial to confirm the validity, accuracy and simplicity of the proposed method. LIST OF SYMBOLS= the load reactance per phase, n.