Flexibility Services Provision by Frequency-Dependent Control of On-Load Tap-Changer and Distributed Energy Resources

Abstract

Distribution network connected distributed energy resources (DER) are able to provide various flexibility services for distribution system operators (DSOs) and transmission system operators (TSOs). These local and system-wide flexibility services offered by DER can support the frequency (f) and voltage (U) management of a future power system with large amounts of weather-dependent renewable generation and electric vehicles. Depending on the magnitude of frequency deviation, other active network management-based frequency control services for TSOs could also be provided by DSOs in coordination with adaptive control of DER. This paper proposes utilisation of demand response based on frequencydependent HV/MV transformer on-load tap-changer (OLTC) operation in case of larger frequency deviations. The main principle underlying the proposed scheme lies in the voltage dependency of the distribution network connected loads. In this paper, it is also proposed to, simultaneously with frequencydependent OLTC control, utilise reverse reactive power-voltage (QU)-and adaptive active power-voltage (PU)-droops with distribution network connected DER units during these larger frequency deviations, in order to enable better frequency support service for TSOs from DSO networks. The effectivity and potential of the proposed schemes are shown through PSCAD simulations. In addition, this paper also presents a holistic and collaborative view of potential future frequency control services which are provided by DSO network-connected resources for TSOs at different frequency deviation levels.

Performance Assessment of TSO–DSO using Volt-Var Control at Smart-Inverters

“…The explanation of such control methods is widely presented in many scientific publications [27][28][29] , but the authors would like to highlight a few key points relevant to the control strategies used in this paper and how they are implemented in the power systems simulation environment. The technological advances on PEC and the new IEEE std 1547-2018 makes the smart-inverter a desirable solution to provide Volt-var control and positively impact the distribution systems.…”

Promising Grid-Forming VSC Control Schemes Toward Sustainable Power Systems: Comprehensive Review and Perspectives

“…Incidentally, uncertain and intermittent renewable generations can greatly affect the performance and economic condition of power systems [17]- [20], [21]. Most importantly, frequency deviations due to lack of inertia are common operational problems with high RES penetrations [22]- [25]. To lessen these technical issues, power utilities and system operators have established administrative codes in the case of integrating RESs into the main grid (transmission and distribution system levels).…”

Future Renewable Energy Communities Based Flexible Power Systems

“…In this regard, system operators need more flexible energy resources to control the system frequency. Different levels of frequency deviations require different flexibility services [38]. Small-scale flexible energy resources such as prosumers need to be aggregated by an aggregator or in a form of energy communities to provide frequency control services.…”