Working principle and characteristics of induction generator

Also known as "asynchronous generator". An alternator utilizes the interaction between the rotating magnetic field in the air gap between the stator and the rotor and the induced current in the rotor winding. The rotating direction of the rotor is the same as that of the rotating magnetic field, but the rotating speed is slightly higher than the synchronous rotating speed of the rotating magnetic field. It is often used as a low-power hydrogenerator.

Because of its convenient maintenance and good stability, asynchronous generators are often used as low-power hydro-generators to run in the grid. When the rotor of asynchronous motor is dragged along the direction of magnetic field rotation by the prime mover, and its speed exceeds the synchronous speed, the motor enters the generator to run, and the mechanical energy input by the prime mover is converted into electrical energy and sent to the power grid. At this time, the excitation current of the motor is taken from the power grid.

Asynchronous generators can also be connected in parallel with capacitors, and generated independently by their own remanence excitation (see figure). At this time, the voltage and frequency of the generator are determined by the capacitance, the speed of the prime mover and the load. When the load changes, it is generally necessary to adjust the parallel capacitance value accordingly to keep the voltage stable. Because asynchronous motor can generate electricity independently without external excitation power supply when connecting capacitors in parallel, it is desirable under the condition of stable load. For example, it can be used as a lighting power supply for rural simple power stations, and it can also be used as a backup power supply.

With the increase of transmission voltage in power system and the growth of lines, when the transmission power of lines is lower than natural power, there will be continuous power frequency overvoltage in lines and power stations. In order to improve the operation characteristics of the system, many countries with advanced technology began to study the application of asynchronous generators in large power systems at the beginning of the 20th century, believing that the stability of large power systems can be improved by adopting asynchronous generators. Reliability and economy of operation. On the basis of previous studies, this paper further studies the electromagnetic design of asynchronous generators and the determination of parallel capacity of power stations through application examples, which provides technical support for the popularization and application of asynchronous generators.