A Personal-Computer based Controller for Performance Improvement of Grid-Connected Wound-Rotor Induction Generators

To optimize the operation of wind energy conversion systems (WECS), various types of power electronic converters had been employed between the generator and the grid. Stator voltage control has been used for improvement of power factor in grid-connected induction generators. However, this method reduces the efficiency drastically. Also the control range is limited. Two schemes are presented to improve the performance of grid connected wound rotor induction generators. Scheme-I is used for maximizing efficiency and scheme-II is used for maximizing power factor. Voltage control together with slip control is applied for this purpose. The power-factor, hence the reactive power demand remains nearly constant throughout the range of operation using scheme-II. These schemes are very useful for wind power based generation where wind speed varies over wide range as well as abruptly. A very fast personal-computer based power electronic controller has been developed and tested using very commonly used IC chips at a very low cost. It consists of eight digital and one analog output lines, and four (expandable to eight) digital and eight analog input lines, all controllable and connected to the CPU. A complete control strategy is also presented to implement the control schemes.