A Study On Voltage Building And Sensorless Control Method Of Stand-alone Induction Generator

Induction motors are robust,reliable,cheap and easy to maintain.Thus,they are suitable for stand-alone power generation systems.Traditional stand-alone induction generator based power generation system realizes the self-excitation voltage of induction generator by shunt capacitors at the end of the induction motor,but the voltage will vary with load,so it can only be applied in occasions where the demand for power quality is not high.Only by overcoming the shortcomings of traditional self-excited induction generator can the induction generator be widely used.In this paper,self-excited induction generator based power generation system with capacitance and capacitance-free induction generator based power generation system are studied respectively.Firstly,based on the state equation of self-excited induction generator,the conditions for the successful establishment of the terminal voltage are deduced.Only when the capacitance and speed are within a certain range,the self-excited induction generator with capacitance can successfully establish the voltage.Then,the capacitor self-excited induction generator based power generation system can be stabilized by controlling current of the converter.Due to the existence of shunt capacitors in self-excited induction generator based power generation system,the model is complex,and high-performance control is not easy to achieve,and successful establishment of voltage conditions limits the speed range.Capacitance-free induction generator based power generation system can overcome these shortcomings.In this paper,the voltage building condition of the capacitance-free induction generator based power generation system are analyzed,and the slope of the given value of DC bus voltage in a certain range is deduced.The indirect vector control method is adopted,and the compensation method for the accurate orientation of the rotor flux is given.Besides,the speed sensor is not needed and different rotor speed estimation methods are used at different stages of power generation.Because the speed range of the capacitance-free induction generator based power generation system is very wide,this paper analyses the theoretical optimal current to maximize the torque in the process of power generation,and gives the realization method of the flux weakening control of the capacitance-free induction generator based power generation system.The simulation model is built in Matlab/Simulink software and an experimental platform of 7.5k W stand-alone induction generation system is built to verify the feasibility of the above theoretical analysis.