| Compared with the traditional cycloconverter,the six pulse bivariate cycloconverter can output more abundant frequencies.According to the characteristics of its output frequency,the corresponding closed-loop control strategies for different frequency bands of the six pulse bivariate inverter are studied.To improve the speed regulation performance of the inverter.Firstly,after analyzing the control theory of bivariate no circulating current and no dead zone and the online trigger strategy based on amplitude,and the merits and demerits of the frequency converter in different frequency bands are combined.It is put forward that the closed-loop frequency modulation control strategy is based on online amplitude calculation in the low frequency band,and the closed-loop voltage modulation control strategy is achieved by step change frequency in the middle and high frequency band.Secondly,lay down corresponding control rules according to the mentioned govern strategy.In the low frequency band,the ordinary PID controller is optimized to change the output frequency for closed loop frequency modulation speed.In the medium-high frequency bands,and the phase shifted angle α is changed by closed-loop voltage regulation to adjust the phase-shifting voltage and speed control.Then,the simulation model of AC-AC change frequency closed-loop speed domination is put up in the MATLAB / Simulink,and the corresponding S function is written.The effect of closed-loop control is proved in the simulation model through speed jump and load jump.At last,the closed-loop control means presented in this paper is proved experimentally on the six-pulse AC-AC change frequency velocity regulation system experiment platform.The experimental outcomes indicate that the closed-loop control strategy proposed in this paper can effectively improve the performance of the variable frequency speed regulation system,harden the mechanical characteristics of the motor,and enhance the robustness.At the same time,it can also make up for the speed gap between the frequency stages above the mid-range. |
