Research On High Power Factor Control Technique Of PMSM Drive System

With the great efforts of the country to promote the green and sustainable development,the permanent magnet synchronous motor has been widely applied in the field of industry,transportation,household appliances and other fields due to its small size,high efficiency and simple structure etc.This thesis takes the air-conditioner PMSM drive system as the background.In order to meet low cost,lightweight and other requirements in air conditioning system,and solve the problem of using mechanical position sensor in high temperature and high corrosion environment,low power factor and severe grid side harmonic distortion in traditional air conditioning system,the PMSM position sensor-less control strategy and high power factor control strategy with electrolytic capacitor-less inverter has been deeply studied in this paper.Firstly,the mathematical model of different coordinate systems is deduced according to the structural characteristics of permanent magnet synchronous motor.The vector control scheme of permanent magnet synchronous motor is researched by vector equation and space vector pulse width modulation.The parameters setting method of the PI regulator are analyzed,and the simulation model of PMSM vector control system is built and the control performance is also verified.Aiming at the problems of the large volume,high cost and low reliability of the traditional position sensor technology,a position sensorless technology based on improved sliding mode observer is designed.By adopting the variable boundary layer thickness saturation function and PLL to reduce the chattering problem in the traditional method,the improved robustness and dynamic response capability of the algorithm is verified by simulation.At the same time,aiming at the problem of detecting error of position angle under start-up and low speed,the high frequency signal injection method and IF open-loop startup strategy are analyzed in detail,and the optimal control scheme of motor operation is discussed in conjunction with the operation characteristics and control requirements of the air-conditioning permanent magnet synchronous motor.At present,the electrolytic capacitor used in the driving system has many defects,such as short life expectancy,poor reliability and low power factor on the grid side,and the extra PFC circuit increases the system cost and loss.In this paper,the high power factor control strategy of PMSM drive system without electrolytic capacitor has been profoundly discussed based on the sensor-less control.The relationship between the input power factor and the voltage ripple of the system is analyzed,and the conditions to achieve high power factor are also given.From the point view of system power,the electrolytic capacitor-less control strategy based on power regulation is studied.This paper also proposed the scheme of power compensation based on bus voltage regulation and the over-modulation strategy based on power balance.The simulation results show that the algorithm can realize high power factor and low harmonic content on the grid side.Finally,the experiment platform is used to verify the sensor-less and electrolytic capacitor-less control algorithm.Through the field experiment,the control strategy proposed in this paper has achieved the expected effect of low cost and high power factor of the system,and has high value in practical application.