Robust Co-Optimization of Droop and Affine Policy Parameters in Active Distribution Systems With High Penetration of Photovoltaic Generation

Legacy distribution systems need to adapt quickly to upcoming operating scenarios. The expected growth of electromobility and distributed generation will bring forth many challenges regarding efficient operation. Additionally, the limited communication infrastructure of these networks hinders the applicability of heavily centralized control strategies. In this context, this paper proposes a distributed control scheme for photovoltaic generators. The scheme comprises a local real–time control layer for the synthesis of active and reactive power references, using traditional voltage droop control, along with affine policies to handle the uncertainty associated to solar irradiance and demand levels. The characterization and periodic adaptation of such control scheme is achieved via a global, computationally tractable robust model able to co–optimize both droop and affine policy parameters. Performance is benchmarked via extensive computational experiments against other state–of–the–art distributed and local control strategies. Results suggest the proposed scheme is able to outperform all competitive frameworks. Its performance is also evaluated as a strictly local control scheme obtaining superior voltage regulation as compared to the recommendations in the Standard IEEE 1547.8.

I. Introduction

Increasing penetration of distributed generation (DG)—mainly photovoltaic (PV)—poses challenges regarding voltage control and efficient operation of distribution systems. Traditional apparatus such as transformers equipped with tap changers and switched capacitors have been rendered insufficient to deal with the uncertain and fast–changing nature of renewable energy supply due to their mechanical limitations [1]. Alternative power electronic devices such as SVCs and STATCOMs respond fast enough but are too expensive to be widely deployed [2]. On the other hand, voltage source converters (VSCs) interfacing DG can control their active and reactive output fast enough and at a low cost, enabling real–time control.