The Research On Transient Process And Power Factor Control Theory Of Doubly-fed Motor Which Using Bi-variants Cyclo Converter

Double variable cyclo-converter can realize no circulation naturally withoutdetection device that can detective the current zero, change the current on the fragmentof a voltage naturally according to the range of the current commutation. But for thedoubly-fed open-loop speed control system using the dual-variables cyclo-converter, thecurrent zero-crossing point of the rotor side is fixed, the phase angle of rotor voltageand rotor is concerned with load size, speed and V/F, this is the feature of doubly-fedmotor control system that used dual-variables cyclo-converter. For it, doubly-fed motorpower factor control law of dual-variables cyclo-converter will be studied in this paper.To control the doubly-fed motor control that used dual-variables cyclo-converterwhen the phase of variable frequency power source and induced emf of the rotor isuncertainty, the control law in the power factor of doubly-fed motor is found in thisprocess,. Firstly, the author deduced the vector graph of doubly-fed motor according tothe control law, found that a theory in accordance with experimental results throughanalyzing many of vector graph. Secondly, with the combination of the dual-variablestheory, the doubly-fed motor control system that constituted by the dual-variablescyclo-converter and winding motor was designed in the MATLAB environment, thetransition process of the doubly-fed motor including its starting process and speedadjusting process is simulated, and verified the feasibility of the starting program.According to the control theory in the power factor that complied with this doubly-fedsystem, the power factor of doubly-fed motor running in the steady state is controlledand the simulation results verified the correctness of theoretical. Finally, theexperimental study about the transition process of the doubly-fed motor usingdual-variables cyclo-converter was carried out and max speed error was obtained underthe different frequencies so that the wound motor can meet a smooth transition to thedoubly-fed motor, summarized the law of max speed error. Power factor control of thedouble-fed motor was also studied, power factor control laws on the stator side and therelationship between stator current and rotor current was consistent with the theory,verifying the correctness of the deduced doubly-fed motor power factor control theory.