This paper presents a control strategy for a doubly fed induction generator (DFIG) using an indirect matrix converter, which consists of an input side matrix converter and an output side voltage source converter (VSC). The capability of the input converter to generate different "virtual dc link" voltage levels is exploited. The commutation of the VSI with reduced voltage is illustrated for operating points where the output voltage demand is low without any deterioration of the current control performance. The proposed method leads to a reduction in the commutation losses in the output converter and reduced commonmode voltage. For the input converter, soft switching commutation is obtained by synchronizing the input and output converter pulsewidth-modulation patterns. This modulation strategy is particularly applicable in DFIG applications because the required rotor voltage decreases when the DFIG speed is close to the synchronous speed. The complete control strategy is experimentally validated using a 2-kW rig.Index Terms-AC machines, machine vector control and space vector pulsewidth modulation (PWM), matrix converter (MC).

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In this work, the control of a Doubly fed induction machine using an indirect matrix converter, connected between the stator and the rotor, is presented. Unlike the traditional scheme, where two back-to-back PWM inverters are used, this converter eliminates the use of bulky DC link capacitors and provides an all silicon solution for direct AC-AC conversion, with sinusoidal input currents and close to unity power factor operation. The machine rotor currents are controlled applying vector control approach with a reference frame aligned with the stator flux vector. The scheme is experimentally verified using a 3kW variable speed energy system prototype. A TMS320C6713 DSP is used as a control platform and experimental results are presented for operation from below and above synchronous speed both in steady state and transient conditions.