Research On Control Strategies Of Permanent Magnet-assisted Synchronous Reluctance Motor

Permanent magnet-assisted synchronous reluctance motors have similar structure design of synchronous reluctance motors.By inserting non-rare earth permanent magnet materials such as ferrite in the rotor barrier,the torque density of the reluctance motor can be improved.Compared with permanent magnet synchronous motors,permanent magnet-assisted synchronous reluctance motors have lower manufacturing costs and do not require complex production precudure.They have received extensive attention in the field of low-cost AC speed regulation.However,the electromagnetic torque of the permanent magnet-assisted synchronous reluctance motors contains two parts: reluctance torque and permanent magnet torque.The torque ripple is relatively large,and specific control strategies needs to be adopted to improve the operating performance of the motor.This paper proposes a new model-free predictive control method,and establishes the firstorder ultra-local current model of the permanent magnet-assisted synchronous reluctance motor.By decomposing the stator dq-axis current change in each control cycle,two components is obtained.One is the current natural response component involved with the motor operating conditions,and the other is the current forced response component affected by the voltage vector.The motor controller uses the voltage vector and current change in the adjacent control period to separately decouple the current natural response component for real-time calculation,in order to achieve the effect of fast tracking.A recursive least squares observer is designed to estimate the parameters of the voltage vector to the current,so as to calculate the forced response component of the current.A model-free predictive control method of the permanent magnet-assisted synchronous reluctance motor with a small amount of calculation is realized in this paper.The simulation and experimental results show that the dynamic and static performance of this method is better than the traditional model-based predictive control method.The proposed method has better self-adaptation ability and good application prospects.The vector control of permanent magnet-assisted synchronous reluctance motors usually uses the 45° current angle control method of synchronous reluctance motor.However,due to the presence of ferrite in the rotor,this control method is not the maximum torque per ampere control,which is likely to increase copper loss in the motor and decrease efficiency.The calculation process of the maximum torque per ampere operating point usually requires the use of the electromagnetic torque equation of the motor,which involves the motor inductance and flux parameters.In this paper,the Lagrange multiplier method extreme value equation is established with the stator current as the constraint condition,the calculation formula of the maximum torque per ampere operating point of the permanent magnet-assisted synchronous reluctance motor is deduced,and the inductance parameters obtained by the observer are applied to the calculation process of current command.Compared with the traditional 45° current angle vector control method,the maximum torque per ampere control method proposed in this paper can effectively reduce the stator current and increase efficiency under different operating conditions by using the inductance parameters obtained by online estimator.