Research On Asymmetric Steady-state Operation Of Self-excited Induction Generators

To meet practical requirements in engineering, the electrical connections of three-phase self-excited induction generators(SEIG) are various when supplying different kinds of loads. Apart from the symmetrical operation, SEIGs are also used to supply single-phase loads in isolated power systems for air-condition or lighting devices.Moreover, even if the three-phase loads are in symmetrical condition, the manufacture of exciting capacitors or aging of wires may also result in the unsymmetrical operation of three-phase SEIGs.When supplying single-phase loads, there are many electrical connections for SEIGs,including the star- or delta- connection in stator or one-, two-, even three-capacitor connection. These connections on one hand extend the application of SEIGs, but also increase the difficulties for analysis on the other hand. Since the load voltage and frequency in steady state operation are crucial parameters to judge the quality of electric power, an effective way to describe the electric machine system and calculate the relevant variables in mathematics is of significant values in engineering. In condition of the fact that the SEIGs studied in this paper is initially designed for three-phase symmetrical operation, it is not likely to reach its best performance in single-phase operation. So, some parameter is supposed to be proposed for the judgment of their performance.This paper lists several single-phase operation connections in common use and introduces the loop-impedance method as well as two-port network method with the generalized load concept. The compound sequence method proposed in the third chapter combines the advantages of both former methods and is then utilized in the analysis of Fukami connection. The effects of capacitors, loads and rotor speed on performance characteristics are discussed and the current balance factor is also defined. The impedance balance model proposed in the forth chapter is deduced with the improved Steinmetz connection. The best capacitor combinations are computed with the optimization of current balance factors. Crucial loads in single-phase operation is also studied in this chapter. Another new method called current balance model is proposed in the fifth chapter to analyze the three-phase unbalance operation. The good agreement of experimental data and calculated results verifies the validity and accuracy of these steady-state models.