Sensorless Rotor Position Detection using Differential High Frequency Phase Current method

Abstract

A new sensorless detection scheme is proposed in this each of these techniques have their merit and limitation. Of paper. This detection scheme is based on a new concept of high -'ur particular interest, a rotor position sensorless detection frequency small-signal phase inductance (L.) of Permanent scheme is required to allow ultra low speed operation and Magnet Synchronous Motor (PMSM), as detailed in this paper. startup with full torque. The most appropriate technique so far The L. of a Soft Magnetic Composite (SMC) motor was mapped is the use of high frequency or pulse injection to detect the in the experiment and the results were used to build a high frequency SIMULINK model for the simulation of a new saliency of the PMSM [4, 5]. Saliency of the PMSM is sensorless rotor detection scheme. mainly caused by two domnant effects: Structural saliency such as the interior permanent magnet synchronous motor Keywords: -Permanent Magnet Synchronous Motor, (IPMSM), and magnetic saturation of the stator which appears Sensorless Rotor detection, Soft Magnetic Composite motor, High in all type of PMSMs. In this paper, a new small signal frequency injection inductance L,, is defined and a novel high frequency injection technique is presented using the LS, principle. List of symbols II DEFINITION AND SIGNIFICATIONS OF Lss vs Line to neutral stator terminal voltage (V) The basic electrical model for a Permanent Magnet is Stator line current (I) Synchronous Motor (PMSM) can be represented as: X flux linkage (Wb) Xpm flux linkage of permanent magnet (Wb) v = Ri + -(1) X rotor speed (electrical) (radsl) s S dt Or rotor angle (electrical) (rad) e, stator flux vector angle (electrical) (rad) assuming X is linear and = Lsis+XpmcosO, then R rotor resistance (Ql) L, synchronous inductance (H) dis Vh peak voltage of injected high frequency signal (V) Vs = Ris + LS dt pm sin Or (2)ih peak current of injected high frequency signal (I) COb frequency of injected high frequency signal (Hz)In general, the above equations represent the behaviour of the motor when it is modelled as an 'electrical-mechanical' I INTRODUCTION.conversion device.In order to control a permanent magnet synchronous motor However, when the saturation of the core material is taken into (PMSM), the information on rotor position is required by the account, X is no longer linear. Fig.1 shows the B-H curve of controller in order to generate the correct phasing of the three-the Somaloy 500 material. Due to its relatively 'soft' B-H, phase stator drive current. Traditionally, rotor position characteristic, the assumption of a linear X over the operating detection is usually by means of resolver or encoder attached range becomes inaccurate. The flux linkage k(i,er) is a to the motor shaft. These position sensors are either very function of the instantaneous drive current is, and the position expensive and/or highly sensitive to environment factors such of the permanent magnet of the rotor Or; both quantities as temperature, noise and vibrations etc. The elimination of determ...