Determination of Currents in an Autotransformer Stator Winding of an Autonomous Asynchronous Generator Connected as a Double Star

Abstract

The use of asynchronous generators in agriculture is restrained by an insufficient degree of voltage and frequency stabilization. Along with the known advantages, such as higher reliability, lesser mass and overall dimensions, high quality of electricity, application of asynchronous generators is hampered by the insufficient level of voltage frequency, which results in need to use additional control schemes or an inverter transformer, as applying of high power load can lead to de-excitation of an asynchronous generator. The use of autotransformer stator windings allows us to connect capacitors to a higher voltage, which will reduce the capacity needed to excite the generator. It is possible to stabilize the voltage of the generator by powering on additional capacitors or by adjusting the rotation speed. The capacitor switching algorithm for stabilizing the voltage of the asynchronous generator must provide the required voltage level, monitor the current in the stator winding in order to prevent the emergency state, and take into account significant demagnetizing starting current when the motor load is applied. The use of an autotransformer version of the stator winding in asynchronous generators allows it to be divided functionally into two parts—a common and a magnetizing one. When determining the currents of an autotransformer winding, it is necessary to take into account the angle between these parts and the load power factor. Correct determination of the parameters of the autotransformer winding will reduce the demagnetizing effect of the load current.