Inrush currents of induction generators due to abrupt connection to utility power networks

The squirrel‐cage‐type induction generator is suitable for small water power stations and wind power stations because of its simple and rugged structure, and low construction cost. However, the transient rush current flows into the primary and secondary windings when an induction generator is connected abruptly to a utility power network. The inrush current causes the voltage fluctuation in the power system. Therefore, electric power companies need a control method with low cost of the inrush current of the induction generator. Many properties of the inrush current must be known in detail. The factors affecting inrush currents are system voltages, control of the system voltage phase angle, rotary speed, residual magnetism of the core, and residual electric charge of the primary windings. In this paper, the inrush current is analyzed by the instantaneous value symmetrical coordinates. The experimental study of the inrush current using phase control equipment and a small induction generator is presented. The conclusions of this investigation are summarized as follows: (1) The factor that gives the strong influence on the inrush current is the voltage phase angle. (2) Although rotary speed changes from 0.9 to 1.15 times as much as the synchronous speed, the maximum value of the inrush current is nearly constant. (3) The maximum amplitude of the inrush current is definitely seen in the first or second wave.