Review on potential strategies for transmission grid operations based on power electronics interfaced voltage sources

In the near future, transmission grids will include an increasing share of directly connected voltage source converters. These systems should be able to support the utility grid autonomously. The present paper reviews the most popular approaches to address the challenge of proper load sharing amongst multiple parallel inverters applied to the utility grid case. Originally developed for Microgrid or UPS applications, these decentralized controls mimic a conventional synchronous generator based system steady-state behavior and showed suitable effectiveness to reach the desired operating point. However, the operations at the transmission grid level bring additional stress on the converters and require transient capabilities. Physical limitations of semi-conductor based converters fundamentally differ from a conventional synchronous generator. Therefore the paper illustrates how the usual real power controls may lead to undesirable behavior during transient events. This raises new issues for reliable operations of interconnected VSCs at transmission level.