Research On Discrete Frequency Soft Starting Controller Based On DsPIC

Traditional soft starter can reduce starting current by regulating SCR triggerangle, meanwhile it restrains starting torque, which makes it not suit for starting withheavy-load. Discrete frequency-control soft starting technique, which keeps thestructure of electronic soft starter, modifies amplitude and frequency of voltage bycontrolling the power frequency half-wave in software, so it can meet the demandsof starting current and torque. This paper studies the characteristics, controllingstrategy, software and hardware design of the starting method.In this paper the principle of modifying amplitude and frequency of voltage isdiscussed, the influence on the phase of first-harmonic of generated voltage isanalyzed, the best triggering mode of every frequency is proposed, and startingfrequencies of motors are chosen. In order to reduce harmonics and optimize the outputwave, triggering mode of equivalent sine is introduced. In order to realize the betterswitching of different frequencies, a novel speed measuring method based on powerfactor without speed sensor is proposed. Because of the influence of power factorangle, the combination control of trigger angle and power factor angle is introduced,which ensures the stability of starting. In order to make the motor perform in energysaving condition, come up with an optimized method.Secondly, a simulation model of discrete frequency-control soft starting ofthree-phase asynchronous motors is designed. The simulation results show theaccuracy and feasibility of proposed scheme.At last, discrete frequency-control soft starting system based on dsPIC30Fserials including the hardware and software is designed. Experiment related tosystem design is done.