Dual-Ascent Optimization for the Provision of Ancillary Services in Three-Phase Low-Voltage Microgrids

Controllable distributed electronic power converters (EPCs) populate low-voltage microgrids. EPCs serve as interfaces between local energy resources, such as renewables or energy storage systems, and the grid, enabling effective power control. Apart from the primary active power control provided by the EPCs, which typically should adhere to local constraints (e.g., maximum power extraction from renewables), functionalities such as reactive power and unbalanced current compensation can be provided, to enhance the microgrid operation. This work proposes a control algorithm for the optimal provision of reactive power, unbalanced currents, and zero sequence powers by distributed EPCs. By incorporating these compensation terms, the power quality at the connection with the upstream grid is enhanced while achieving an optimal sharing of the compensation effort among the EPCs. The approach optimizes the overall system efficiency, using converter power losses as an optimization criteria. The proposed method combines the dual-ascent technique with the simplex algorithm for solving the problem.