Performance Assessment of TSO-DSO using Volt-Var Control at Smart-Inverters: Case of Vestfold and Telemark in Norway

Abstract

The massive penetration of distributed energy resources (DERs) in distribution networks provides a strategic opportunity for the distribution system operator (DSO) to coordinate the assets appropriately and offer services to the transmission systems. The IEEE std. 1547-2018 introduced a control mechanism to enable the power electronic converters (PECs) to offer several services, including voltage regulation by controlling the reactive power injection/absorption; this type of PECs is also known as "smart inverter". The participation of the smart-inverters in the voltage regulation with a novel customer-centred piece of legislation and markets provide the DSO with powerful tools to enforce very positive TSO/DSO interactions. This research paper presents a comprehensive assessment of the steady-state performance provided by voltage control at the smart-inverters to the TSO- DSO system. The assessment includes analysing main indicators using time series considering short term (24-hours, 1-minute resolution) and long-term (one-year) horizon. In this paper, the three leading indicators are used as criteria for the assessment: total energy losses voltage profile in the TSO-DSO system and the power flow interaction at the interface between the systems. The assessment is based on numerical results using the DIgSILENT PowerFactory simulation tool, where the voltage controllers have been implemented, and regional electrical system in south-eastern Norway, the area of Vestfold and Telemark as been used for illustrative purposes.