Improved Field Oriented Control for Switched Reluctance Machines with Large Step Response Capability

Switched reluctance machines (SRMs) are typically powered by unipolar current excitation, but the complexity of the traditional drive method requires the optimization of the turn-on angle and turn-off angle complicating the design of the torque controller. To address this issue, field-oriented control (FOC), commonly applied to brushless machines, is adapted for SRM drives. This approach applies a sinusoidal current with a DC offset to each circuit, rather than the conventional trapezoidal current. To the authors knowledge, the critical issue related to large speed steps with classical FOC has never been studied before and can cause problems because the control cannot effectively control the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d q 0$</tex> currents in the rotor reference frame and it is not possible to reach the speed reference with a step. The same speed reference can be reached with a slow speed ramp reference. In this paper, two control strategies are proposed to improve the FOC, thereby extending the step response capability of the drive. Simulations are included to evaluate the effectiveness of the proposed approaches with respect to the classical controls.