Electronically controlled bi-directional connection of induction generator with a single-phase grid

The use of cage-rotor three-phase induction generator (IG) presents considerable advantages mainly due to its robustness and low cost. However, the low performance in terms of voltage and frequency stabilization is an important drawback when trying to guarantee power quality to the load. This paper contributes in presenting an IG-basic structure which employs power-electronic converters associated with an induction generator in order to improve both voltage and frequency operation characteristics of the system. Moreover, the proposed structure does not require the use of a speed governor to the generator, which simplifies the application of systems in micro-hydroelectric power plants in rural areas. The use of single-phase distribution lines to supply rural areas has been a common practice at utility companies. This study proposes some alternatives to connect three-phase inductor generator power plants to the single-phase grids. The grid works either supplying additional electric power to AC local loads or absorbing the exceeding generated power. The power-electronic converters are controlled by a DSP-based control which determines the power flow and the current waveforms at different points of the systems. The characteristics and limitations of each different approach are presented and discussed considering power quality aspects. The analysis and simulation results are validated by experimental data.