Research On Phase Current Reconstruction Method Of Single Sensor In Motor Control System

Phase current information is an important parameter for inverter circuit control and protection.How to obtain current information reliably and accurately is the key to realizing high-performance control of an AC drive system.The traditional current detection system uses more than two current sensors to detect current information,which not only raises the cost and size of the controller but also causes measurement errors in the sensors and lowers the control performance when used for an extended period of time or in challenging environments,which restricts its application in high-precision and high-reliability situations.The phase current reconstruction method of single current sensor has progressively caught the interest of researchers.In this paper,the problems of unobservable area,sampling errors,and current ripple in the process of phase current reconstruction of single current sensor are studied,and a proposal is made for corresponding suppression strategies.Firstly,the principle of multi-sensor high-end current detection,low-end current detection,and composite current detection methods is analyzed around the current detection problem of three-phase bridge inverter circuit in an AC drive system;from the aspects of pulse width modulation waveform adjustment,voltage vector synthesis,and state observation,three perspectives are used to evaluate the DC bus single current sensor’s current detection method;the multi-position coupling current detection method is analyzed from the intermediate bridge arm coupling,upper-lower bridge arm coupling,and multi-position coupling;the mechanism and solution of the current detection error from the two aspects of inherent error and sampling error are reviewed and analyzed.Subsequently,the existence mechanism of the unobservable area and sampling error in the DC bus sampling process is analyzed.By shifting the phase of the PWM waveform in the unobservable area and constructing a complementary effective vector,a zero-point drift error suppression method based on random space vector pulse width modulation(RSVPWM)is proposed,and the zero-point drift error self-detection and self-correction of the reconstructed current are realized.The experimental results show that the reconstruction error of the proposed zero drift error detection method is less than 3.1%,which is 65% lower than that before correction,and the distortion rate is lower than 5.32%.Finally,the reason and mechanism of the increase in reconstruction current distortion caused by the change in sampling position due to the existence of an unobservable area are analyzed.The current sampling window that meets the minimum sampling time is constructed by RSVPWM to complete two consecutive samplings,and the mean value of the two samplings is obtained in the same-phase dynamic current.A mid-point value random space vector pulse width modulation reconstruction strategy is proposed,which realizes the reconstruction suppression of the current ripple.The proposed control strategy does not need to insert redundant voltage vectors,has a small amount of calculation and is not limited to specific PWM techniques.According to experimental results,the suggested ripple suppression and reconstruction technique lowers the maximum ripple amplitude by 44%,and the reconstruction current THD increases by 1.71%.