Research On Model Predictive Control For Permanent Magnet Synchronous Motor Drive System Fed By Three-phase Three-level Inverter

With the development of the motor control technology,power electronics technology and detection technology,Permanent Magnet Synchronous Motor(PMSM)is the first choice for the development of motor drive system.For the control algorithm of permanent magnet synchronous motor,first proposed control strategies are magnetic field orientation control and direct torque control.However,both of them control strategies have their own advantages and disadvantages,which can not guarantee the optimal control of motor control system in terms of dynamic characteristics,robustness and so on.The advanced control algorithm needs to consider the inherent characteristics,nonlinear and other factors of the system.Finite Control Set Model Predictive Control(FCS-MPC)is a high-performance on-line optimization control algorithm.The FCS-MPC method has low complexity.For the system constraints between control variables,it has strong processing power.So,the FCS-MPC program has become an important branch of research in the field of motor control over the past several decades.Compared with the traditional field orientation control and direct torque control,FCS-MPC can significantly reduce the electromagnetic torque ripple,reduce the switching losses of the inverter,and improve the dynamic performance of the system.The development of power electronic technology has made the motor drive system free from the limitation of the conventional two-level inverter topology,and the combination of multi-level inverter has become a new idea.The output voltage of the multilevel inverter is much higher,so its output waveform is better,and its advantage is obvious in the large-capacity AC speed regulation system.As the research foundation of multi-level inverter,the three-level inverter is the most widely used.And among them,the first choice is the Neutral-Point-Clamped(NPC)three-level inverter.Therefore,Model predictive control for permanent magnet synchronous motor drive system fed by Neutral-Point-Clamped three-level inverter is used as the research object.In the PMSM drive system,the position and speed of detection are very important.And commonly used method is through the mechanical sensor to measure.But this method has many defects in the practical application,which will reduce the stability and reliability of motor system,and increase costs.The speed sensorless technology estimates the actual speed and position information of the motor by detecting the current or voltage in the motor.This method omits the used mechanical sensor and can achieve high precision and high dynamic performance of the motor system.Therefore,PMSM's speed sensorless control technology has become a hotspot in recent years.The main research contents are divided into the following aspects:(1)Based on the same PI speed controller,compared with two MPTC PMSM systems(one is the system fed by two level inverter,the other is system fed by NPC three-level inverter),the performance of the two systems are compared and analyzed.(2)In order to further improve the system response performance,overcome the unknown load torque disturbance and enhance the system robustness,a load torque observer based on ESO is designed,then combine the load torque observer and sliding mode speed controller to get compound controller.(3)The PMSM MPCC system based on fractional order sliding mode observer is designed to achieve a fast and accurate estimation of motor speed.