| Abstract |
This paper describes a method to improve the torque performance of a Switched Reluctance Motor (SRM) during dc-link disturbances, using a voltage-dependent control strategy. Voltage sags or excessive load transients can cause a drop in the dc-link voltage, resulting in a loss of mean torque production of the SRM. A voltage dependent control strategy is presented to obtain maximum mean torque, even at lower voltage levels. Optimal control is defined using a nonlinear model of the SRM with drive, based on finite element flux-linkage data. The torque behaviour of the SRM during dc-link disturbances is analyzed, using the analytical electromagnetic system equations, resulting in optimal turn-on and turn-off angles. When analyzing the electromagnetic system equations of a stator phase, it can be seen that, during a drop in the dc-link voltage, the rotor base speed decreases and field weakening is reached at a lower rotor speed. Anticipating the turn-on angle and injecting the phase current before pole-overlap (low back-emf) is the technique proposed in this paper. Finally, the strategy is integrated into a SRM-drive to maximize the torque during startup of a high-inertia industrial machine. If the acceleration is critical, the resulting dc-link voltage drop must be taken into account to reach an optimal control with maximum mean torque production. The considered SRM is a 8/6 SRM with a three level current hysteresis controller. |
