Synchronisation method for three-phase PWM converters under unbalanced and distorted grid

A new open-loop synchronisation method for three-phasePWM converters connected to the utility grid is proposed, which gives good performance under distorted and highly unbalanced grid voltages. Moreover, it has a better performance in terms of distortion in the synchronisation signals when compared with other open-loop methods. It has a good transient performance for frequency, phase and amplitude disturbances when compared with closed-loop methods. 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 synchronisation method.