| Permanent magnet synchronous motors(PMSM)are widely used in various occasions due to their excellent performance.In the drive system of the permanent magnet synchronous motor,large-capacity electrolytic capacitors are generally used to maintain the stability of the bus voltage and ensure the smooth operation of the motor.However,electrolytic capacitors are large in size,high in cost,poor in reliability,and have high requirements on the working environment,which has become a weak link restricting the development of motor controllers.The use of small-capacity film capacitors instead of large electrolytic capacitors has become a new research hotspot,which is of great significance for improving the service life of the controller and reducing the system cost.However,the low capacitance of the bus bar thin-film capacitor will result in a power factor,the power quality of the grid side will be worse,too.On the other hand,the LC filter circuit on the grid side of the system will cause LC resonance while suppressing the high-order harmonics of the input current on the grid side,which will introduce high-order harmonics and affect the system stability.In order to solve these problems,this paper studies the high power factor control strategy and harmonic suppression method of the PMSM motor drive system without electrolytic capacitors.The main means of this paper lies in behind.First,the model of the nonelectrolytic capacitor drive system was founded,including the mathematical model of the PMSM.Then the transformation theory and the common PMSM control algorithm has put on.Based on the characteristics of the non-capacitor PMSM drive system,the input of the grid and output of the inverter power are analyzed,and the causes of LC resonance are analyzed,this has proved the possibility of non-electrolytic capacitor drive system theoretically.Secondly,due to the small-capacity bus bar capacitance,the input voltage on the grid side turns into half-sine waves,and the output power of the inverter was fluctuated heavily,resulting in the problem of low system power factor.In this paper,a high power factor control strategy based on inverter power control is studied.After analyzing the power relationship between the inverter and the input current of grid side,a closedloop method of the inverter power is proposed.Because of the fluctuation of the grid power,the gain The PIR controller with better effect realizes the closed-loop control effect,and gives the parameter selection process to achieve the control goal of high power factor on the grid side,and the high power factor method is verified by simulation.In the grid side,LC resonance of the drive system should be solved,a resonance suppression strategy based on bus voltage feedback is proposed by analyzing its generation mechanism,extracting resonance information,and designing a reasonable feedback loop.The virtual resistor is connected in series with the grid-side inductor,that is,the active damping of the bus voltage and inductor current feedback is fed back,and the system damping is increased through feedback control to suppress resonance.Feature extraction of specific frequency harmonics,design feedback loop and increase system damping,suppress LC resonance,and propose a bus voltage distortion compensation method to further suppress grid-side current harmonics and make the system meet IEC-61000-3-2 harmonic standard,and also used simulation to verify the resonance suppression effect of the designed method on the system.Finally,a software and hardware experimental platform based on the TMS320F28335 was used,and the schematic drawing,PCB design,welding and debugging of the electrolytic capacitor-free driver are carried out.The power factor and current harmonic content of the non-electrolytic capacitor PMSM drive system at different speeds are verified on the experimental platform.It is proved that the system constructed in this paper is workable and has good performance in improving the power factor and resonance suppression of the system. |
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