Permanent Magnet Synchronous Motor System Control Based On Small Capacitance Power Converter

With the rapid development of power electronics technology and power converters,permanent magnet synchronous motor drive systems have been widely expanded in many fields such as railway traction,electric vehicles,robots,CNC machine tools,household appliances,etc,and it is developing in the direction of intelligence and miniaturization.The DC-link of the traditional permanent magnet synchronous motor drive system usually parallels the large-capacitance electrolytic capacitor to stabilize the DC-link voltage and realize the power decoupling of the front and back stage.However,the shortcomings of electrolytic capacitors,such as large size,short life,and high cost,seriously affect the reliability of the system.And grid-side current distortion,which makes it difficult to meet the EN61000-3-2harmonic standard.The use of small capacitors instead of large DC-link capacitors can effectively reduce the system volume and improve system reliability.In this paper,a small-capacity DC-link capacitor is used to replace the large-capacity electrolytic capacitor to form a small-capacitance power converter permanent magnet synchronous motor drive system.However,the exchange of DC-link capacitors will cause DC-link voltage fluctuations,which will affect the performance of the motor.In order to solve this kind of problem,this paper has carried out research on its related control strategy.By adding an active power decoupling circuit and combining the relevant control strategies proposed in this paper,it aims to ensure the power factor of the power grid while ensuring the rated operation of the motor.The main work of the paper is as follows:First,analyze the defects of the traditional permanent magnet synchronous motor drive system DC-link electrolytic capacitors,discuss the feasibility and practicality of using small-capacity DC-link capacitors,and analyze the possible problems after the use of power decomposition circuits,it also introduces the research status at home and abroad from the aspects of control strategy and topological structure.Secondly,the mathematical model of the permanent magnet synchronous motor system of the small capacitor converter is introduced,the mathematical model of the permanent magnet synchronous motor in different coordinate systems is established,and the power characteristics of the permanent magnet synchronous motor drive system of the small capacitor power converter are analyzed,and analyzed the coupling relationship between the input power of the grid and the output power of the motor,the energy storage of the DC-link capacitor and the impact of the reduction of the DC-link capacitor on the performance of the motor are introduced.The control strategy of the traditional small capacitor converter permanent magnet synchronous motor system is introduced.Then,the working principle of the DC/DC converter and the setting process of main electrical parameters are introduced,and a control strategy without voltage surge is proposed.Aiming at the shortcomings of traditional large DC-link capacitors,a control strategy based on harmonic current injection to reduce DC-link capacitors is proposed through theoretical analysis.Finally,a system hardware platform based on TMS320F28335 as the core control chip was built,and the software control program of the drive system was written.On this basis,the method proposed in this paper is verified through simulation and experiment.The results show that the small-capacitance power converter permanent magnet synchronous motor system control strategy proposed in this paper can achieve higher system power factor and excellent motor performance.