Indirect Torque and Stator Reactive Power Control of Doubly Fed Induction Machine Connected to Unbalanced Power Network

The paper deals with the methods of either stator current or rotor current vector control of doubly fed induction machine connected to the unbalanced power network. Several alternative control targets, such as fixed electromagnetic torque, symmetrical stator current, or symmetrical rotor current, have been achieved. In spite of the selected target, the stator current is sinusoidal, however in some cases, it is unbalanced. The proposed vector control methods do not use separate negative sequence calculation and control. In some targets, filtration of signals is required in order to achieve symmetrical reference variables (positive sequence), which can be either stator or rotor current depending on the assumed target. Laboratory tests results have been presented in the steady state, as well as in transients. Short comparison of stator and rotor current controllers has been made on the basis of the laboratory test results.