Adaptive Sensorless Control Strategy For Low-speed Operation Of Pmsm With High-frequency Signal Injection

With the deepening development of the electrification process,in the field of intelligent manufacturing,the motor system plays a major role as the core component of energy conversion.Permanent magnet synchronous motors(PMSMs)are widely applied due to the advantages of high efficiency and high-power density.As for the field-oriented control(FOC)used in the PMSM drives,the accurate rotor position information is important for effective decoupling.However,the position sensor will increase the volume and cost of the system.Besides,affected by the extreme environments,such as high temperature and high pressure,etc.,the position sensor cannot be installed in the system.Hence,the sensorless control technology based on the position self-sensing of the motor has been widely concerned.The high-frequency signal injection(HFSI)method is an effective scheme to control the sensorless reliable operation of PMSM at low speed.At present,there are still some key problems to be solved in this method,which mainly include the initial rotor position detection,the parameter self-tuning,the rotor position offset error compensation,and harmonic error suppression,etc.Based on the industrial application requirements,this dissertation researchs the above key issues to realize the adaptive sensorless control of low-speed operation for PMSM drives.The initial rotor position is an important information to realize the reliable startup of the system.The HFSI methods are applied to detect the rotor magnetic pole position and the double pulse signal is injected to identify the magnetic polarity in the traditional method,which leads to the discontinuous detection process and the annoying noise problems.A random high-frequency(HF)square-wave voltage injection based initial rotor magnetic pole position and polarity identification method for PMSM is proposed in this dissertation.By extracting the induced random HF current in the stationary frame,the initial magnetic pole position can be estimated.Next,a signal processing method based on the accumulation of the induced random HF current peak is investigated to identify the magnetic polarity simultaneously.In order to improve the accuracy of the magnetic polarity detection,a saturated peak current delay compensation strategy is studied to reduce the digital delay effects.The proposed method can detect the magnetic pole position and the polarity simultaneously by utilizing the signal processing of random HF current,avoiding the large-amplitude pulse voltage injection,which reduces the additional noise.When the HFSI based methods are applied to the sensorless FOC control of low-speed operation of PMSM,the injection signal parameters,closed-loop controller parameters,and position observer parameters have an important influence on the position estimation accuracy,the transient-state and the steady-state control performance.A multi-objective absolute error integral optimization based parameter self-tuning strategy of HFSI method is proposed.These parameters are tuned offline by utilizing the parameter self-learning and the model analysis.Then,an adaptive law with the average of integral of absolute error as the tuning rule and with the speed ripple and torque ripple as the optimization index is designed to adjust the controller and observer parameters online.As for the extraction of the integral of absolute error,a moving window based error detection method is investigated,avoiding the issues of mistuning and tuning delay.The proposed method combines the offline and online tuning,which ensures that the system can start smoothly and improves the steady-and transient-state low-speed operation performance,realizing the adaptive debug-free operation of sensorless PMSM control system for HFSI method.For the issues of the rotor position observation offset error caused by the cross-saturation effect and other nonideal factors in HFSI based methods,a current vector angle adaptive adjustment based rotor position offset error compensation strategy is proposed.By adjusting the current vector angle adaptively and obtaining the amplitude and phase information of the two different current vectors respectively,the rotor position offset error can be detected online adopting analytical geometry method combined with the characteristic of electromagnetic torque of PMSM,realizing the adaptive compensation of error.Since the current vector angle can be adaptively adjusted according to the load conditions in the proposed scheme,the issues of low signal-to-noise ratio at light load and large current amplitude fluctuation at heavy load in the traditional compensation method can be effectively solved.This method does not require the offline measurement or the finite element analysis,and has a satisfactory compensation effect for the position offset error under different load conditions,which improves the performance of the sensorless control algorithm.Affected by the inverter nonlinearities,the flux spatial harmonics,the current measurement error,and other factors,there is a great harmonic error in the observation result of rotor position,thus resulting in torque ripples,which deteriorates the low-speed operation performance of the sensorless control system.An adaptive iterative learning control based rotor position harmonic error suppression strategy is proposed.By constructing the proportional-type iterative learning rotor position observer with the forgetting factor to obtain the tracking error and generate the compensation value in real time,this method can online suppress the rotor position harmonic error effectively.An iterative learning gain self-tuning strategy is investigated,improving the suppression ability of position harmonic error under different operation conditions.The proposed method does not need to distinguish the causes and frequencies of the harmonic error and has a good suppression effect for harmonic error components caused by different factors,which reduces the torque ripples of sensorless PMSM control system.Finally,the digital algorithms of the proposed control methods are realized on the experimental platform of sensorless PMSM drive.In addition,the experimental tests of startup performance and low-speed operation performance of sensorless system are carried out.The experimental results validate the effectiveness of the proposed adaptive sensorless control strategies of HF signal injection for PMSM drive,which can provide the theoretical and technical support for the implementation of high-performance sensorless control system.