Compensation of Interpolation Error for Look-Up Table-Based PMSM Control Method in Maximum Power Control

Abstract

This paper proposes a compensation method for interpolation error of the maximum power control of a PMSM control system that generates current commands through a look-up table. A torque control system using a look-up table created through experiments has superior characteristics, such as control stability and torque accuracy, compared to a system that executes torque control via a linear controller based on modeling. However, it is impossible to generate information on all the currents for the output torque in the table. Therefore, because the data stored in the look-up table have a discrete characteristic, they are linearly interpolated to generate a current command for the torque command. However, the PMSM current trajectory is generally elliptical, which causes an error owing to linear interpolation, reducing the maximum output power. In particular, when the table data are insufficient, such as in the high-speed operation range, the reduced maximum output cannot be ignored. This paper proposes a compensation method for the interpolation error using two feedforward compensators and a PI controller, which was verified through experiments.

On the Development and Experimental Validation of a Novel and Intuitive Interior Permanent Magnet Synchronous Motor Controller for Electric Vehicle Application

“…The viability of implementing the lookup table in the PMSM controller has been reported by several researchers [19,20]. They were both employing the torque and rotational speed of the PMSM as the inputs of their controllers.…”

“…They introduced a feedforward interpolation compensation error for different ranges of the PMSM operation. The authors of [19] focused on the performance evaluation of their proposed controller in the fieldweakening region while [20] focused their research on the maximum power control region. Their lookup table contains a discrete torque map.…”

“…However, the linear interpolation method does not match the nonlinear characteristic of PMSM. The authors of [20] added a compensation block to correct the linear interpolation using DC-link voltage feedforward and obtain precise output torque from the limited data. Later, Ref.…”

“…Moreover, they make the controller easily reprogrammable to work with any electric motor in the same class. These performance curves also contain information on the working envelope of electric motors and ensure the controller no longer needs its limiter values (as in the case of [19,20]) after they have been incorporated using the torque and field-weakening lookup tables. Furthermore, the lookup table aids the safe operation of the controller by integrating the maximum value of torque, current, and current ramping up in the system.…”

Improved Voltage Flux-Weakening Strategy of Permanent Magnet Synchronous Motor in High-Speed Operation

“…It determines the most appropriate current point to drive the motor to control the speed, thereby enabling the user to sufficiently obtain the output torque ability of the motor. In addition, a method of controlling the motor by conducting various experiments on the motor and making the characteristics of the lookup table was used [22][23][24]. However, it has shortcomings in that it requires accurate information on parameters because it is sensitive to changes in motor parameters, and the control design is complicated because the variation characteristics of magnetizing inductance should be considered.…”