Virtual admittance PLL structure for grid-forming power converters in microgrids

Synchronization plays a fundamental role in connecting power electronic converters with the grid. Conventionally, the synchronous reference frame phase-locked loop (SRF-PLL) has been widely used to estimate the grid phase angle. Though SRF-PLL is effective under normal grid voltage conditions, its performance degrades drastically under weak grid conditions. This paper presents a control strategy for current controller of grid-connected power converters that contributes in the reduction of the negative effects of SRF-PLL during grid disturbances. The main control concept is based on virtual admittance. This approach is capable of operating effectively power converters when connected to weak grids and permit grid-forming operation. Simulation and experimental results are provided to validate the proposed controller.
This project has been partially funded by Spanish Ministry of Science Innovation and Universities under the project RTI2018-100921-B-21 and the H2020-LC-SC3-2018-ES-SCC project Interrface GA824330.
Peer Reviewed
Postprint (published version)