The Study On The High Frequency Signal Injection Method For PMSM Sensorless Control Strategy

Recently,Permanent magnet synchronous motors (PMSM) have found wide applications due to their high power density, high efficiency,easy of control, high torque-to-inertia ratio and high reliability.For the control of the PMSM drives such as the vector control and the direct torque control, the rotor position is required to perform commutations between phases and to control speed and torque too. In the typically application can be the rotor position obtained by using mechanical speed (position) sensors like an encoders or resolvers.Unfortunately, the use these sensors will increase the overall cost and weight of the systems and next reduce the reliability and noise immunity of the systems. Research in the area of sensorless control of the PMSM is beneficial because of the elimination of the feedback wiring and it makes the systems more reliable and cheaper.In the past,different schemes have been proposed for PMSM sensorless control. Among them one group is methods based on motor fundamental equations. Rotor flux is considered as sinusoidal distributed, which neglects motor space harmonics and other secondary effects. Then motor back-EMF can be used to estimate rotor position from motor fundamental equations.These methods are either open loop structure ,such as direct calculating, back-EMF integration, etc. or closed loop observers ,such as MRAS, Extended Kalman Filter, D-state obserber,Sliding Mode Observer, etc. In this paper, high frequency signal injection PMSM sensorless control is researched detailedly.Firstly,this paper presents a method using rotating high frequency voltage injection to estimeate the rotor position for an PMSM.The scheme utilizes motor magnetic saliency property which contains the information of the rotor position due to magnet saturation, A high frequency voltage signal is injected in the stationary frame in order to detect the magnetic saliency and estimate the rotor position. The filters are used to analyze high frequency current and to extract rotor position information. In the conventional method, the use of the band pass filter and band stop filter can take the serious problem of phase-shifting and amplitude attenuation. Because the high pass filters have zero magnitude for any constant (DC) signal and have the ability to completely eliminate a specified frequency,A synchronous frame filtering take the place of the band pass filter and band stop filer。In addition,the rotor position estimation method based on Luenberger observer is discussed in detail.according the magnetic saturation effect,. A method has been proposed to distinguish the polarity of the rotor magnet,which solves the problem that estimate result would be reverse with the traditional method based on high frequency signal injection.At last,the fluctuating high frequency voltage signal injection were discussed in the thesis,this scheme uses fewer filter and have a simpler configuration ,this method also possesses better speed adjustable performance both in static and dynamic.In order to verify the proposed control scheme, simulation is carried out. The results show that the method is effective to detect initial rotor position correctly,motor position and speed are also properly estimated in the low and high speed region without any speed or position sensor.