New Synchronization Method for Three-Phase Three-Wire PWM Converters under Unbalance and Harmonics in the Grid Voltages

This paper proposes a new open-loop synchronization method for three-phase three-wire PWM converters connected to the utility grid. It presents a better performance in terms of distortions in the synchronism signals if compared with other open-loop methods. Moreover, it has a good transient performance due to both angle and frequency disturbances, as well as input currents with low total harmonic distortion (THD) when used to synchronize PWM rectifiers, even under unbalanced and highly distorted grid voltages. In addition, a frequency adaptation algorithm is proposed for applications where large frequency variations are expected, such as in weak grids. Experimental results using a DSP TMS320F2812 are given to demonstrate the good performance of the proposed synchronism method