1phi SOGI phase locked loop with secondary control path in grid-connected power converters

Abstract

The performance of digitally controlled gridconnected power converters depends to a large extent on the synchronization strategy. Single-phase phase locked loops (PLL) with a second-order generalized integrator (SOGI) as quadrature signal generation subsystem provide proper grid synchronization in the case of harmonically distorted grid voltage. The SOGI-PLL transient performance can be improved by replacing the PLL by a frequency locked loop (FLL). However, compared with SOGI-PLLs, SOGI-FLLs perform poorly in steady-state. This work proposes to include a secondary control path (SCP) to improve the dynamics of SOGIPLLs, while maintaining the steady-state performance. Simulation and experimental results are provided to validate the proposal.