Distributed methodology for reactive power support of transmission system

Abstract

This paper deals with the provision of reactive power support from distribution grids to the transmission system. To this end, a new distributed control scheme is proposed that coordinates the reactive power output of distributed generation (DG) units to meet a predefined reactive power set-point at the point of interconnection of the distribution grid with the transmission system. The coordination process is implemented in an optimal way minimizing the network losses, while also satisfying the technical limits of the distribution grid. Furthermore, the proposed distributed control scheme is supplemented with a new control algorithm for the on-load tap changer (OLTC) of the high-/medium-voltage transformer to unlock additional reactive power flexibility in case the voltage limits at the distribution grid are reached. Time-series simulations on the IEEE 33-bus network are performed to evaluate the performance of the proposed method against existing solutions.