A study on doubly-fed induction machine with bi-directional AC/DC/AC converter

A high power factor three-phase boost AC/DC/AC control system for a doubly fed induction machine (DFIM) is proposed and simulated in this paper. This converter has two back-to-back 3-arm bridges with DC bus linked electrolytic capacitor, thus the AC/DC module and the DC/AC module can be controlled separately. The AC/DC block is space vector controlled as a high power factor rectifier and the inverter controls the DFIM by a stator-flux oriented vector control strategy. Dynamic simulations show the high power factor of the converter as well as the speed adjusting system controlling the motor speed below or over the synchronous speed rapidly as expected. The reactive power seen from the stator side is also adjustable in the corresponding range. It is concluded that the AC/DC/AC converter works well and it can be designed very compactly. It is an alternative way for the three-phase AC/DC/AC converter used to control the DFIM.