New formula to determine the minimum capacitance required for self-excited induction generator

The induction generator is the most common generator in wind energy systems because of its simplicity, ruggedness, little maintenance, price, etc. The main drawback in an induction generator is its need of reactive power means to build up the terminal voltage. But this drawback is not an obstacle today where PWM inverters can accurately supply the induction generator with its need from reactive power. The minimum terminal capacitance required for an induction generator to build up is the main concern. Most previous work uses a numerical iterative method to determine this minimum capacitance. But the numerical iteration takes a long time and divergence may occur. For this reason, it cannot be used online. A new simple formula for the minimum self-excited capacitance required for induction generators is presented here. By using this formula, there is no need for iteration and it can be used to obtain the minimum capacitance required online. A complete mathematical analysis for an induction generator to derive this new formula is presented.