PLL parameters tuning guidelines to increase stability margins in multiple three‐phase converters connected to weak grids

This study investigates the stability of multiple three‐phase converters connected to weak grids. It has been derived a flexible modelling regarding the number of converter and type of collector system. The both eigenvalues and impedance based methods are applied to the stability analysis. The eigenvalues method is used to give guidelines on the choice of the phase‐looked loop (PLL) gains. To improve the stability margins, the increase in the PLL damping ratio is proposed. Moreover, it is used to investigate the PLL interaction with converter current and DC bus voltage controllers. The impedance based method extends the stability analysis to multiple three‐phase converters. In addition, it has been used to show the effects of converter current and DC bus voltage controllers parameters on the stability margins. Finally, in order to validate the theoretical analysis, time‐domain results with hardware‐in‐the‐loop are given, showing a strong correlation with the theoretical analysis in the frequency domain.