Research On Phase Current Reconstruction Algorithms For PMSM Wide Operating Range Based On Single Current Sensor

Permanent Magnet Synchronous Motor(PMSM)servo system has been widely used in modern industry.High-performance servo system requires accurate detection of winding current.High-precision current sensors are expensive and occupy a certain volume.Therefore,it is of great significance to reduce the number of current sensors,which can greatly reduce the cost of the system.This paper takes the phase current reconstruction technology as the research object,studies the current reconstruction characteristics of the system in different working ranges,proposes corresponding solutions to the existing problems,and finally studies the suppression of reconstructed current errors.The relationship between the current and the phase current of each branch of the inverter is studied.Based on this,the principle of phase current reconstruction based on the bus current information is analyzed.According to the characteristics of actual sampling,the dead zone of current reconstruction in each zone of the system is analyzed,and the corresponding mathematical model is established.The vector pulse interpolation method can solve the phase current reconstruction problem in the low modulation dead zone,but there is also a problem of large switching loss.Based on the vector pulse interpolation method,the working principle of regular triangle pulse width modulation(RTPWM)is studied.Three effective voltage vectors are used to synthesize a given voltage vector,and the effective working area of the algorithm is deduced.Based on the RTPWM algorithm,a zero vector is inserted between the three effective voltage vectors,thereby reducing current harmonics.The working principle of the shift pulse method in the low modulation blind zone is studied.Aiming at the existing hardware,a pulse shift method is proposed.The above methods are verified by simulations and experiments.The current reconstruction dead region in the over-modulation region is analyzed,and an over-modulation algorithm is studied.Based on this algorithm,a pulse shifting method and a dead region avoidance strategy are proposed to solve the current reconstruction in the over-modulation region.A method to eliminate the current reconstruction dead zone by changing the current sensor mounting position is studied.Based on the introduction of its working principle,a zero-vector interpolation method is proposed for the problem of current sampling in the over-modulation area,which solves the current sampling problem in the over-modulation area.The method of reconstructing the phase current in the whole operating range of the motor is studied.The problem of switching current reconstruction methods in different working ranges is analyzed.Then,a current observer was used to observe the current,and the bus current was collected for correction.Finally,the error of the phase current reconstruction is studied.The theoretical analysis of the existence of DC-offset error and phase delay error is made,and the error suppression methods are proposed.