A Direct Starting Method of Doubly-Fed Induction Machine for Shipboard Propulsion System Application

This paper proposes a method to start a doubly-fed induction machine (DFIM) directly. Firstly, by applying the open-loop control, the three-phase rotor currents are measured at the instant when the stator voltages are close to the DFIM starting voltages. Then, calculate the corresponding open-loop dq rotor currents. After that, the open-loop q-axis rotor current is set as the output limit of the speed regulator, and the openloop
$d$
-axis rotor current is set as the
$d$
-axis rotor current reference value for closed-loop control. Subsequently, increase the stator voltages with the preset dq rotor current reference values applied, and the DFIM can start directly. The proposed starting strategy overcomes the self-start difficulty of DFIM system without using additional equipment and switch-over algorithms. Moreover, from the experimental results, it can be found that the dq rotor currents obtained in the open-loop control are related to the initial rotor position. The method is not applicable for the positions where the open-loop
$q$
-axis rotor current is negative, but it can be overcome by adjusting the initial rotor position.