Position Estimation Method of IPMSM in Full Speed Range by Simplified Quadratic Optimization

In this paper, a new full-speed-range position estimation method for the interior permanent magnet synchronous machine (IPMSM) is proposed. This method is designed for high power traction motor drives. In such application, variable speed operation from zero to high speed is desired. The objective of this paper is to obtain smooth position estimation in full speed range to guarantee high reliability of the motor control system. Firstly, a quadratic cost function based on the stator voltage equations is constructed. The rotor position in the full speed range is obtained by numerically solving an optimization problem. After obtaining the rotor position, the motor speed is then obtained through a phase-locked loop observer. In such a way, only one variable in the optimization problem has to be solved. Therefore, the numeric calculation burden is greatly reduced. The convexity of the quadratic cost function considering sampling noise as well as parameter mismatch is discussed in detail. Thus, the solvability and accuracy of the estimation result is guaranteed. At last, experiments on a traction motor are conducted to verify the effectiveness of the proposed position estimation method.