Study On Three-phase PWM Rectifier Topology For High Frequency Permanent Magnet Synchronous Generator

Nowadays,our country is focusing on the development of aeroengines and gas turbines,High speed electrical machines are widly used in aeroengines,gas turbines,flywheel systems,high speed air compressor,electrically assisted turbo charging systems and high speed spindle applications.As one of the most important structure of the high speed machines,permanent magnet synchronous generator(PMSG)receives more and more attentions.High speed PMSG can employ a PWM rectifier to realize the rectification and DC voltage stabilization,which has better performance than the traditional structure of diode rectifier and DC/DC converter.In high frequency PMSG systems,the PMSG fundamental frequency is close to the switching frequency,thus the carrier ratio is low.Therefore,the control performance of the PWM rectifier is deteriorated.In order to overcome the technical problem of low carrier ratio,in this thesis,two-level and multilevel PWM rectifier topologies are studied for the high frequency PMSG sytem.By increasing the equivalent switching frequency of the rectifier with the same device switching frequency,the performance of the vector control is improved dramatically.Firstly,the mathematical model of the PMSG on d-q reference frame is established and the vector control method is analyzed in detail.Then,the two-level PWM rectifier is mathematically modeled,and improved two-level PWM rectifier topologies are proposed.A unique generation method of the PWM signals corresponding to the improved topology is also introduced.To verify the effectiveness of the two-level PMSG-PWM rectifier system,a simulation model and experimental platform based on an STM32F407 micro controller is built up.Both simulation and experiment results show that the validity of the proposed improved topology and the unique vector control methodology.Finally,the modular multilevel PWM rectifier based on modular multilevel convertor(MMC)is mathematically modeled and the control strategy is studied.Using the simulation results,the performances of the the two-level system and multilevel system are compared.The simulation results verify the effectiveness of the proposed scheme and correctness of the vector control algorithm.