Design of Non-Linear Reduced and Full Order Observers for an Inverter Fed Permanent Magnet Synchronous Motor Drive

Objectives: This paper proposes the state estimation of Permanent Magnet Synchronous Motor (PMSM) by designing and comparing two non-linear observers such as reduced order and full order observers. Methods: Control system design for an inverter fed PMSM drive can be carried out using conventional two loop structure; which are outer speed loop and inner current loop. Conventional control system design uses the classical transfer function approach for Single-Input Single Output (SISO) systems. Proportional plus Integral (PI) controllers were designed for individual control loops. The PI controller transient response is slow, which can be improved through state feedback by using pole placement technique. The State Feedback Controller (SFC) of a PMSM drive requires all the state information. In PMSM, damper winding currents are usually inaccessible and need to be estimated using an observer. Findings: A non-linear reduced order observer is designed in order to estimate the damper winding currents of PMSM where as to estimate both damper winding and stator winding currents a non-linear full order observer is proposed. The performances of two observers for the drive system are verified and compared through the extensive simulations using MATLAB/SIMULINK implementation. Applications: Generally the states of the drive system are estimated using sensors, resulting the cost and complexity of the drive system increases. Also the estimated states are inaccurate due to parameter imperfections. So in order to overcome these problems, one can design a non-linear reduced/full order observer.