Development Of A Series Sixfold AC-AC Frequency Conversion Controller

The frequency conversion speed regulation has the characteristics of good performance and high efficiency in the motor speed regulation method.It is a reasonable choice to use the frequency conversion speed regulation method to improve the system efficiency for fans and pumps.In the field of frequency conversion,there are two major categories of AC-AC frequency conversion and AC-DC-AC frequency conversion.The "phase-hopping" AC-AC frequency conversion studied in this paper achieves AC-AC direct frequency conversion.Compared with AC-DC-AC frequency conversion,the price is lower and the cost can be better.Compared with the traditional AC-AC frequency conversion method,it has the advantage of a larger frequency conversion range.However,the previous research work on the "phase-hopping" AC-AC frequency conversion only realized the triple-phase "phase-hopping" AC-AC frequency converter,and there is still a problem that the harmonic content is large and it cannot be put into practical use.The purpose of this study is to design a series of six-phase "phase-hopping" AC-AC converters,and expand it to a six-fold AC-AC converter circuit on the basis of the triple AC-AC converter circuit to reduce the system harmonics to a practical level,and Adding the closed-loop speed regulation and fault detection mechanism to the control part makes the six-fold AC-AC frequency converter form a complete closed-loop control system,which can be put into use as a product.The work done in this article mainly includes:1.Introduce the system design idea of series six-phase "phase-hopping" inverter.The controller hardware circuit is designed with STM32 module as the main control board and FPGA as the secondary control board,and the corresponding design of the two control boards is designed.Control software flow.2.Analyzed the mechanical characteristics of the asynchronous motor,considering the discrete characteristics of the series six-fold AC-AC frequency conversion,combined with the mechanical characteristics of the motor to design a stepped speed control strategy,taking 37.5Hz,42.86 Hz,45Hz and other frequencies as examples The hierarchical speed regulation strategy is explained.Simultaneously,a model of theclosed loop speed regulation system of the six-level AC-AC frequency conversion controller is built in SIMULINK,and the closed-loop speed regulation control idea is verified by simulation.3.Taking into account the safety of actual use,the failure type of the sixfold AC-AC frequency conversion circuit is analyzed,and the fault detection link is designed in conjunction with its complicated circuit structure,and the efficiency of fault recognition is improved by introducing the concept of petri nets.Large-scale commissioning provides a convenient way to troubleshoot.Based on the fault simulation of the series six-level AC-AC converter,the triode P11 was used as an example to establish the petri net model.The stateflow tool was used to simulate and analyze the designed petri net fault identification,which verified the effectiveness of the petri net fault identification method..4.The experimental platform of the six-level AC-AC frequency conversion controller was built,and five sets of output voltage waveforms with a frequency interval of less than 1 Hz were obtained.The experimental results initially verified the theoretical analysis,but due to time and condition constraints,the closed-loop speed regulation process could not be achieved.And fault diagnosis links are implemented on the experimental platform.