Research On Field Oriented Control Based On Sensor-less PMSM

Permanent magnet synchronous motor has many advantages,such as good control performance and high power factor.It has been widely used in various fields.At the same time,sensorless control is also a hot research topic in the field of motor control in recent years.Based on the theoretical analysis of sensorless control algorithm and magnetic field oriented control strategy of permanent magnet synchronous motor,this paper mainly focused on the improvement of stator flux observer and control method respectively.In the sensorless control strategy of permanent magnet synchronous motor,flux estimation method is one of the most simple and effective methods to estimate rotor position and speed.Based on the analysis of the traditional flux observing model,this paper introduced several common improvement schemes for the initial value error and DC offset caused by the pure integration link.Then a flux observing model based on the cross compensation method to improve the precision of the flux observation was proposed.The practicability of the improved method was proved by simulation.In terms of control strategy,according to the characteristics of the surface-mounted permanent magnet synchronous motor itself,the control method of i_d=0 was chosen as the implementation scheme of this paper.An improved FOC control strategy was proposed based on the original control method.On the one hand,the speed loop is used to directly output u_q to improve the dynamic performance of the system.On the other hand,when the motor load is disturbed,the current limit value of i_q is set to prevent the damage to power device caused by the sharp rise of current.The simulation results showed that the improved method not only improves the dynamic performance of the system,but also has good robustness and stability.Finally,the hardware and software system of sensorless permanent magnet synchronous motor were designed with NM1120 as the main control chip.The experimental results of the cross-compensation-based flux observer and the improved FOC control strategy were verified respectively.The experimental results demonstrated the effectiveness and reliability of the two schemes.