Modified direct torque control for saturated interior permanent magnet synchronous motors

Abstract

Purpose

To optimize the performance of direct torque‐controlled interior permanent magnet synchronous motor drives, the purpose of this paper is to modify the constraints and strategies of such a control while accounting for magnetic saturation.

Design/methodology/approach

The machine model used to investigate the proposed method is the conventional two‐axis machine model, which is modified to include magnetic saturation in the quadrature axis. With the consideration of magnetic saturation, all optimal strategies, which correspond to the maximum torque per ampere and field weakening strategies, and motor‐inverter limitations are derived in T−|ψ_s| plane to apply in the direct torque control (DTC) method. Such strategies which take magnetic saturation into account and determine the optimal torque and flux commands are derived and implemented in DTC method.

Findings

Using the modified strategies ensures that the machine capacity is applied as much as possible. Simulation results emphasize the applicability and effectiveness of the proposed control process.

Research limitations/implications

In order to use the proposed method, it is necessary to define quadrature‐axis inductance as a function of quadrature‐axis current. Since, in this method, a simplified function is applied, it is not required to know exact magnetic behavior of motor and this simplified function can be easily obtained using finite element softwares.

Practical implications

Using the proposed method in practice results in better dynamic operation as well as maximal usage of the motor capacity.

Originality/value

This paper deals with consideration of magnetic saturation in DTC method which is not done in pervious works.

Citation

Majidi, B., Milimonfared, J. and Malekian, K. (2010), "Modified direct torque control for saturated interior permanent magnet synchronous motors", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 29 No. 1, pp. 126-138. https://doi.org/10.1108/03321641011008000