Performance evaluation of decoupled control of rotor torque and rotor electric power in a salient pole synchronous machine

This paper presents the performance of a closed loop current control drive system which provides independent control of rotor torque and rotor current in a salient-pole synchronous machine. The machine is modeled using a d-q equivalent circuit in the rotor reference frame. The analysis shows that if the rotor current and its derivative are continuous functions, it is possible to derive equations for both the d and q axis stator currents that control the electric power transferred to a resistive load mounted on the rotor and independently control the rotor torque. The drive system is affected by factors included in the derived d-q axis stator currents. The effect of these factors, namely, d-q axis inductance, command rotor current, and flux perturbation frequency is investigated using both simulation and experimentation. Further, the effect of increasing interpolar cut-out on both rotor torque and rotor electric power is investigated. The technique eliminates the need for slip rings. The machine would find such uses as in rotational antenna and turret systems, or other situations where power is required for an electric load mounted on a rotating assembly.