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This paper describes the influence of magnetic saturation on sensorless control for interior permanent magnet synchronous motors (IPMSM). A novel sensorless control algorithm for IPMSM using 3-phase high frequency voltage input is proposed. Rotor position is estimated by simple integration procedure independently of motor parameters. Taking magnetic saturation into consideration, local inductance is directly calculated by finite element method. Calculated inductance well agrees with experimental value and the influence of magnetic saturation on motor inductance value is evaluated. It is shown that magnetic saturation causes large estimation angle error of sensorless control for IPMSM, and a method that reduces estimation angle error is proposed. The validity of proposed method is confirmed by experimental results.

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This paper describes the analysis of sensorless control considering the influence of magnetic saturation and inverter operation. 3-phase high frequency voltage input gives information on rotor position by simple integration procedure as follows.Where A t is a coefficient determined by induced voltage and motor reluctance variation. I uh , I wh is high frequency current of U-phase and W-phase excited by induced high frequency voltage, respectively. Using these I c and I s values, rotor position is estimated by an observer as follows.Where θ,θ andω denotes rotor angle, estimated angle and estimated angular speed, respectively. θ e denotes estimated angle error θ −θ, and Θ e gives an approximation of sin 2θ e ≈ 2θ e (θ ≈ 0), independently of motor parameters. The transient response of motor current is analyzed by nonlinear voltage equation as follows.These partial differentials are calculated directly by finite element methods analysis considering magnetic saturation. Highspeed analysis is realized by the interpolation of partial differential data table of flux-linkage. And the use of the geometric relation of the motor magnetic circuit can reduce the amount of data. Figure 1 and Fig. 2 show simulation and experimental results of sensorless control. The estimated angle error shows a periodic tendency to increase in both results. Motor torque declines at points where large angle error exists. Figure 3 and Fig. 4 show simulation and experimental results of the biased convergent point observer. The biased convergent point observer derived from the analysis results enables significant improvement of the characteristics of sensorless control. These results show excellent correlation with experimental results. The proposed method is very useful for designing control algorithms considering the influence of magnetic saturation. Masayuki Sanada * * MemberYoji Takeda * * Senior MemberA high-speed analysis method for 3-phase high frequency voltage input sensorless control of interior permanent magnet synchronous motors (IPMSM) driven by pulse width modulation (PWM) inverters taking magnetic saturation into consideration is proposed. By using finite element method (FEM) analysis, partial differential values of fluxlinkage can be calculated directly and precisely in a short time. High-speed analysis of motor voltage equations is realized by interpolating table data of calculated partial differential values and using simplified power device models. The geometric relation of motor magnetic circuit and redundancy of motor current help reduce the number of points in table data. Analyzed results are well fit in with experimental results and the validity of proposed methods is confirmed.