Ancillary Service Provision via Primal-Dual Based Coordination of Distributed Power Electronic Converters in Three-Phase Microgrids

Electronic power converters are extensively applied in microgrids to interface distributed energy resources to the grid. Besides the primary active-power control, electronic converters support increasingly advanced and flexible control capabilities. While the former is typically bound to local needs (e.g., maximum power extraction from renewables), additional degrees of freedom can be exploited to support microgrid operation. This article proposes a control algorithm that allows the optimal provision of reactive power, negative-sequence, and zero-sequence currents by distributed converters. The resulting operation shows enhanced power quality at the point of common coupling (PCC) and limited conversion losses, which are taken into account in the optimization algorithm. Three modes of operation are discussed, that is,
i
) power loss minimization;
ii
) balanced currents at the PCC;
iii
) zero reactive power flow at the PCC. An algorithm based on the primal-dual method is proposed to solve the optimization problem. Results based on experimental measurements are discussed to prove the effectiveness of the proposal.