Research On Low Cost Permanent Magnet Synchronous Motor Drive System

With the high performance and low price of the permanent magnet material, the permanent magnet synchronous motor (PMSM) has been widely used in the industry and low cost home appliance because of its high efficiency, simple structure, low inertia, high torque-current ratio, low noise and no excitation loss. Aiming at the low cost appliance of PMSM, this paper studied two control methods for the low cost control of PMSM:the high efficiency V/f control method for the motor without damping windings and the vector control method based on low resolution hall-effect sensors.First, aiming at solving the problems of poor stability and low efficiency of the PMSM with V/f control, an improved compensation method for the voltage vector based on the analysis of active and reactive power was investigated. After the analysis of the speed variation with the power angle, a digital damping loop was established to improve the stability. The amplitude of the voltage vector was compensated by observing the reactive power with that under the MTPA control. The method was presented to achieve the stable control based on active power observer and MTPA control strategy based on reactive power observer.Then, this paper also studied the control of PMSM based on low resolution position sensors. An improved rotor position estimation method in PMSM with low-resolution hall-effect sensors was proposed. This method promises to decrease the estimated position errors, which are caused by the hall position offset. A linear interpolation based on least squares method is used to estimate the rotor position. The space vector pulse width modulation (SVPWM) strategy based on the estimated rotor position was used to control the PMSM.Finally, the simulation based on MATLAB/Simulink was built to validate the availability of the control system. The high efficiency V/f control method and the vector control method based on hall-effect sensors were both experimented on the drive system for an exterior rotor motor. The simulation and experimental results both validate the effectiveness of the proposed methods.