Research On High Frequency Trigger Strategy Of Cycloconverter Based On Real-time Control

The traditional cycloconverter controls thyristor trigger angle to achieve variable current,so the output frequency is low.With the development of the theory of biphasic phasing control,the output frequency of the cycloconverter reaches 1/2 power frequency.The bivariate six pulse cycloconverter increases the output frequency of the cycloconverter to 42.85 Hz,making it possible to use the high frequency section of the cycloconverter,which is also of great significance for the efficient operation of asynchronous motors.This paper introduces the development and trend of frequency conversion technology and AC-AC conversion at home and abroad firstly.Then the principle of bivariate control is introduced.Based on the previous research results,the basic formula of AC frequency conversion frequency output is analyzed,and all the output frequencies of the high frequency section of the six pulse AC frequency converter are found out.Then from the practicability of the frequency of the high frequency section,according to cosine intersection method and waveform assembling principle,considering the symmetry,sine degree and three-phase balance degree,the available output waveforms under high frequency full voltage and partial voltage are found out.Then Determining trigger strategy according to the optimal output waveform of each frequency band and realizing online.To verify the speed control effect of the trigger strategy in the high frequency section,Under the MATLAB/SIMULINK module,the simulation model of the cycloconverter speed control system is build,and the corresponding S function is compiled.and verify the control effect under the ideal condition through the simulation experiment.The control effect in ideal condition is verified by simulation and experiment.Then,combining with the existing equipment in the laboratory,a variable frequency speed control system platform with STM32 as the control chip is built.A lot of simulation and experiment are carried out,and the results are compared with the theory,and the trigger control strategy of the high frequency section of the six pulse AC converter is summarized and summarized.The simulation and experimental results show that the high frequency real-time trigger strategy has better control effect,whitch can realize the stable operation of high frequency under arbitrary frequency and make the motor running smoothly and have a certain loading ability.And the waveform of current and voltage has good sine and symmetry.