Frequency-dependent control of DERS and OLTCS in the future distribution networks

Abstract

In the future, large amount of flexibility is needed from different voltage levels to fulfill the flexibility needs of the transmission and distribution system operators (TSOs and DSOs) in increasingly renewables-based power systems. This paper develops further the TSO-DSO coordinated, frequency-dependent distributed energy resources’ (DERs’) and on-load-tap-changers’ (OLTCs’) control scheme for the future electricity distribution networks to enable prioritized flexibility services provision for the TSOs and DSOs by proposing dynamic adaptive and frequency-dependent current/thermal limits utilization for distribution network lines, cables and transformers as part of the overall scheme. In addition, the paper focuses on comparison of tan(phi)=-0.35 as reactive power (Q) control method for solar photovoltaics (PVs), tan(phi)=-0.35 (discharging) / 0.4 (charging) for battery energy storages and tan(phi)=0.4 for electric vehicle (EV) chargers instead of previously proposed frequency-dependentQ-control principles for DERs. Also the effect of more rapid PV active power (P) fluctuations as well as further modified active power-frequency droop (Pf-droop) settings in MV BESS’s multi-use cases with PV and EV are studied by PSCAD simulations.