AC currents synchronization technique based on the normalized phase-locked loop for modulation of a three-phase PWM delta-switch rectifier

The three-phase PWM delta-switch rectifier is an unidirectional topology that presents interesting features, such robustness and high efficiency. Most of the delta-switch rectifier modulation strategies require current sector identification in order to properly apply the according voltage vectors. This is typically neglected in power factor correction applications due to the low displacement angle. However, in wind power generation applications the rectifier is directly connected to an electric generator and the synchronization process is not straightforward. In this context, this work proposes a phase-locked loop strategy based on the direct measurement of the rectifier ac currents and compares its performance to other strategies through theoretical and experimental analysis.