Research On The Fast Start-Up Method Of Permanent Magnet System Motor Sensorless Control

Permanent magnet synchronous motor(PMSM) uses permanent magnet to produce the air gap flux without the need for additional excitation, leading to its high power density, small volume, light weight and other unique advantages. Because of its many advantages, PMSM has been widely used in many industrial applications. The current control method of PMSM drive system mainly are the vector control and direct torque control, both methods can realize the precise control of motor speed and torque, thereby gaining excellent performance o f speed adjustment, but inevitably needs to get accurate rotor position information. The rotor position can be measured by mechanical sensor, but the installation of mechanical sensor increasing the system cost and complexity, reducing the stability and anti-interference ability of the system. So the sensorless control of PMSM has become a current hot topic in the field of motor control, while the start-up under the condition without position sensor is the difficulties of this research topic.This paper mainly launches the research for the rapid start-up of PMSM without position sensors.Firstly, this paper gives a brief introduction to sensorless control strategy of PMSM and commonly used method of sensorless start-up, sets up the mathematical model of PMSM and analyses the vector control and sensorless control based on sliding mode observer.Secondly, this paper mainly research the start-up method of PMSM under the condition without position sensor, according to the three-stage method for motor starting, respectively study the rotor initial position location, open loop speed, state switch. In the stage of rotor initial position location, this paper puts forward an improved method of voltage vector injection. Compared with the traditional voltage vector injection method, a pair of positive and negative direction of voltage vector s after the second batch of voltage vector s to motor are applied, the amplitude and duration are both increased compared to the previous two batches of vectors, leading to that the response current has more obvious influence on the i ncreasing and decreasing magnetic of the d axis N/S pole, in this way the method can avoid the poles misjudgment. In addition, when dealing with the response current after the second batch of voltage vectors have been processed, use its opposite direction inductance difference validate the result of the current judgment, which can ensure the accuracy of the current judgment result. In the stage of open loop speed, use I-F open loop speed and current closed-loop control mode, which can assure good dynamic performance. In the stage of state switch, a strategy based on current amplitude changing has been used. This paper proposes a current control method by changing slope, the slope of the current changing in the late of switch state transition process is slower than that of the early. In this way, time interval of transition process is shorten on the premise of that the current has no obvious fluctuation at the state switch point, making the motor switch smoothly from the open loop control mode to the double closed-loop control mode.Finally, make a modle of the stage of open loop speed and state switch in the MATLAB environment, then build an experimental platform using TMS320F2808 of TI company as main control chip to verify the improved voltage vector injection method and control strategy of open loop speed and state switch. Simulation and experimental results proved the feasibility and effectiveness of the proposed control strategy. It can make PMSM start up fastly and smoothly without position sensor, which has high engineering practical value.