Adaptive DER and OLTC Control Scheme for Flexible Distribution Grids

Abstract

Flexibility needs of distribution and transmission system operators (DSOs and TSOs) are constantly increasing in renewables-based power systems. In this paper, the TSO-DSO coordinated, adaptive on-load-tap-changers’ (OLTCs’) and distributed energy resources’ (DERs’) control scheme for the future flexible distribution grids is further studied and developed. The focus in PSCAD simulation studies with simplified HV/MV/LV network is on cases with two LV feeders which have various types of DERs connected to them with different types of control schemes. This paper studies, for instance, the effect of reactive power (Q) -flow-based control of MV and LV battery energy storage systems (BESSs) to minimize upstream reactive power flows as well as compares tan(phi)=-0.35 as reactive power control method for solar photovoltaics (PVs), tan(phi)=-0.35 (discharging) / 0.4 (charging) for BESSs and tan(phi)=0.4 for electric vehicle (EV) chargers to the previously proposed and studied reactive power control principles of DERs. In addition, further improved MV/LV OLTC blocking logic to ensure stable operation is presented.