Optimal Speed Control For Interior Permanent Magnet Synchronous Motor Single Rotor Compressors

Because the asynchronous motor in the single rotor air-conditioning compressor often operates at a fixed frequency,it cannot run at high speed for fast refrigeration,nor can it run at low speed for energy saving;In addition,when the pressure is high,it is particularly difficult to start the asynchronous motor,and the power density of the asynchronous motor is often not as high as that of the permanent magnet synchronous motor,so the compressor needs to have a larger volume to achieve the same power level.Therefore,the interior permanent magnet synchronous motor without position sensor gradually replaces the traditional asynchronous motor in the single rotor air conditioning compressor to realize the speed regulation function.From the perspective of energy conservation and emission reduction,energy efficiency grade market access indicators and cost savings,the drive control of single rotor air conditioning compressor based on permanent magnet synchronous motor has attracted manufacturers to conduct more in-depth research.However,the crankshaft of the single rotor compressor is asymmetric,and there is only one suction and exhaust process in a mechanical cycle,so the load at the motor end fluctuates periodically with the mechanical angle,which leads to new problems in the sensorless motor drive control: difficult to start under high pressure,unstable operation at low and high speeds,and easy to get out of control.The research of this paper aims to solve these difficulties in the operation of single rotor compressor,which will help promote the wide application of permanent magnet synchronous motor in single rotor compressor,and help achieve the goals of "double carbon" and energy conservation and emission reduction.The research object of this subject is the single rotor compressor,which is driven by the permanent magnet synchronous motor with sensorless control.This paper focuses on the zero speed start,high-speed flux weakening stable operation and low-speed stable operation of the single rotor compressor,and optimizes the speed regulation methods under different working conditions to improve the performance of the single rotor compressor.In view of the problems of this research,the main research contents are explained from the following aspects.(1)Using high frequency current control based on resonance to solve the problem of uncontrollable induced current of pulse high frequency voltage injection methodThe following two improvements are proposed for the traditional pulsating high-frequency injection method: Firstly,in order to make the amplitude of high-frequency current controllable,reduce manual debugging and make the pulsating high-frequency voltage injection method more practical,a current resonance controller for high-frequency current control is introduced in the loop where high-frequency voltage is injected.Because the frequency of the control signal is relatively high,the phase compensation of the resonance controller needs to be carefully studied to obtain good current control effect.The phase compensation angle is derived from the lagging phase of RL system.Secondly,because the injection signal frequency is also higher than the control frequency,considering the discrete design of the resonance controller,the zero pole matching method is used to discrete the resonator to ensure the stability of the resonant point and the adjustment rate of the resonance controller.(2)Phase locked loop with phase advance compensation and adaptive angle error compensator are used to improve the accuracy of angle observationThe research on the stability of high-speed flux weakening operation of single rotor compressor is mainly divided into the following three aspects: Firstly,according to the characteristics that the speed fluctuation frequency of single rotor compressor is also large at high speed,the inherent phase shift and amplitude attenuation characteristics of phase-locked loop in high frequency band are theoretically analyzed.The existence of error between observation angle and real angle is caused by phase-locked loop.This gives a direction of the research on high speed field weakening control of the single rotor compressor.Secondly,according to the fact that the performance of the flux weakening region is reduced and the current fluctuation is large under the actual working conditions,the influence of the error angle on the weak magnetic performance is theoretically analyzed.According to this influence,it is clear that the primary goal to improve the performance of the weak magnetic region is to improve the accuracy of the observation angle of the weak magnetic region.Thirdly,according to the lag characteristics of phase shift in high-frequency band of PLL,the leading phase compensation scheme and adaptive angle error compensation scheme are studied to improve the characteristics of high-frequency band of PLL and improve the accuracy of observation angle.The stability of the proposed scheme is analyzed theoretically,and the general design method of loop bandwidth is given.(3)Using resonance control and UDE to suppress speed fluctuationThe research on the large speed fluctuation of low-speed of single rotor compressor is mainly divided into the following three aspects: Firstly,analyze the causes of speed fluctuation and build a mathematical model to accurately describe the fluctuation behavior.Based on the mathematical model,the expression of fluctuating load torque is constructed to clarify the relationship between load torque and mechanical position angle.Secondly,in order to reduce the speed fluctuation,the fluctuating load needs to be compensated.The speed control based on PI is limited by the bandwidth,so it is difficult to obtain satisfactory results.In order to compensate the fluctuating load,UDE is used to observe the load fluctuation,and the speed control loop is designed.The performance of UDE control is analyzed in frequency domain,and the Q factor is used to improve the stability of the filter in UDE control.Thirdly,considering the phase-shift of the phase-locked loop,the impact of the phase-locked loop on the periodic fluctuation speed is analyzed.The observation speed is not accurate enough,which will degrade the performance of the UDE based speed fluctuation suppression scheme.Therefore,an additional resonance controller is added to form a resonant phase-locked loop to improve the accuracy of the observation speed and improve the UDE speed control performance.