Accuracy considerations for single-phase digital derivative based AC-grid synchronization unit

Accurate grid synchronization unit is essential for reliable operation of grid converters. Single-phase unit may utilize measured function and its digital derivative as the base for PLL. This paper compares some solutions of accuracy problems typical for such derivative approach: oversampling of measurements, interleaved calculation of derivative and averaged evaluation pulse signals. The proposed methods are described and implemented with a low cost microcontroller. Resulting declinations of space vector and calculated phase angle are compared. It is concluded that all the described methods provide certain accuracy improvement, but measurements in interleaved series are the most accurate method. It is also concluded that the overall evaluation of these methods must include analysis of the hardware and software resources spent for their implementation that requires an extra work.