Research On Sensorless Control System Of Variable Frequency Compressor Based On PMSM

In recent years,variable frequency air conditioning compressor has become the mainstream of the market because of its high temperature control precision,low voltage requirement,small vibration noise,and comfort and energy saving.The permanent magnet synchronous motor(PMSM)is widely used in the field of air compressors because of its simple structure,good speed regulation performance,small driving current and no great impact on the power grid.Therefore,it is of great significance to study the control algorithm of permanent magnet synchronous compressor This paper mainly deals with the control technology of sensorless transducer and the suppression of low frequency torque ripple in frequency conversion compressor.This topic first discusses the vector control technology of PMSM variable frequency compressor,including the theory of coordinate transformation,the mathematical model of compressor in three common coordinate systems,the principle and realization process of voltage space PWM,and the commonly used vector control strategy.Secondly,two kinds of rotor position estimation methods are deeply studied.They are low-speed pulse high frequency voltage injection method and sliding mode observer method suitable for middle and high speed respectively.The basic principle of high frequency injection is to input high frequency sinusoidal voltage signal in the two-phase rotating coordinate system,and then extract rotor position information from the generated high-frequency current response.In this paper,in view of the buffeting problem,a scheme of replacing the switching function with the S type function is given.When the compressor is in high frequency operation,directly through the rotor position information anyway is not accurate,easy to cause the system collapse,this paper introduces the mechanism of phase-locked loop control and compensation of rotor angle estimation and improves the estimation accuracy of rotor.Then,the low frequency torque ripple suppression of compressor is deeply studied.This paper describes the load characteristics,the reasons for the fluctuation of speed and the causes of torque ripple,and based on the commonly used PD iterative learning algorithm,combined with the characteristics of the compressor itself,the optimization is made.The effectiveness of the algorithm is proved by simulation and experimental research.Finally,a system experimental platform is designed,and related research is done on the platform,including low frequency speed fluctuation suppression,system performance test,rotor position estimation and high frequency phase-locked loop analysis,which prove the feasibility of the control algorithm in this paper.