The Phase Current Reconstruction Technique With Single Current Sensor In Vector Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors—PMSM are widely used in industry due to their advantages such as high power density,high reliability,and wide speed range.Among many control strategies,in order to ensure accurate control of the speed and position of the motor,it is necessary to precisely control the electromagnetic torque of the motor.Because the electromagnetic torque of the motor is generated through the interaction of the stator current and the rotor flux linkage,current sensors are independent for obtaining stator currents to fulfill high performance current control.In some special applications,the cost and volume of the motor control system are strict.However high-precision current sensors are usually high cost and large size.Therefore,researchers have proposed with single current sensor sampling branch current to reconstruct all phase currents information,which isphase current reconstruction technology.In this paper,a surface-mounted permanent magnet synchronous motor is the control object,and the vector control strategy with i_d=0 is applied to elaborate the phase current reconstruction technology using DC-link resistance and single isolated Hall current sensor.First,the available install positions of single resistance current sensor and single Hall current sensor,which can realize the phase current reconstruction,is analyzed in detail.The result is that single resistance current sensor can only be installed in the DC-bus,wheras single hall current sensor can installed in many of positions for its couple sampling approach.This paper mainly investgatesoffset problems of the DC-link resistance reconstruction and improves a zero vector sampling reconstruction method with isolated hall sensor.As phase currents reconstruction with single resistance sensor,the sampling dead zone of DC-link current is analysised deeply in this paper.PWM modified method is adopted to solve sampling dead zone.The deviation of DC offset in sampling circuit is analysised and the effect in reconstructed phase current is formulated therotically.An online DC offset conpensation method is proposed to illimulate the dynamic deviation in sampling circuit.In addition,an analogy sampling circuit is designed.The experiments are carried out on a PMSM FOC hardware system with STM32F103controller.The experimental results tested the proposed compensation method feasiablly.Compare with the current control without online compensation,harmonic distortion in phase currents are minimized largely with proposed method.The principle of the reconstruction technology with a single-isolated Hall current sensor,simultaneously coupling two position currents（one phase switch current and the other phase winding phase current）,is analyzed in detail.Namely,the zero-voltage vector sampling method.The advantage of this method is that the suitable PWM switching period is used to calculate the minmum duration T_minwithin thewholelinearmodulation area;the delay of sampling voltage vector output is solved by delaying the sampling points;the utilization rate of DC voltage is improvedthrough dynamic SVPWM modulationstrategy,and the current prediction is performed via interpolation.A simulation model is established in Matlab/Simulink and an experiment based on the PMSM FOC hardware system with STM32F103 controller to verify the practicabilityand effectivenes.