Towards Flexibility Trading at TSO-DSO-Customer Levels: A Review

Abstract

The serious problem of climate change has led the energy sector to modify its generation resources from fuel-based power plants to environmentally friendly renewable resources. However, these green resources are highly intermittent due to weather dependency and they produce increased risks of stability issues in power systems. The deployment of different flexible resources can help the system to become more resilient and secure against uncertainties caused by renewables. Flexible resources can be located at different levels in power systems like, for example, at the transmission-level (TSO), distribution-level (DSO) and customer-level. Each of these levels may have different structures of flexibility trading as well. This paper conducts a comprehensive review from the recent research related to flexible resources at various system levels in smart grids and assesses the trading structures of these resources. Finally, it analyzes the application of a newly emerged ICT technology, blockchain, in the context of flexibility trading.

A Local Capacity Market Providing Local and System-Wide Flexibility Services

“…Flexibility services are typically categorized into systemwide and local services based on the type of system operator (TSO or DSO) utilizing the services [3]. System-wide flexibility services aim to follow load and/or generation variations close to real-time to maintain the system frequency within a permissible level [4]. Hence, system-wide flexibility services are procured by the TSOs.…”

Transactive Energy Market for Energy Management in Microgrids: The Monash Microgrid Case Study

“…It can be achieved through local energy trading or managing load and generation resources for participation in external energy markets. Flexibility service aims to adjust power in a given moment for a given duration in a specific location within the network, which can be achieved through modifying generation and consumption patterns in reaction to market signals [10].…”

Optimized Operation of Local Energy Community Providing Frequency Restoration Reserve

“…However, the utilization of maximum flexible capacity of the whole system requires the contribution of FERs connected to different levels of the network. These levels include DSO-and TSO-levels [5]. Electric vehicles (EV), different types of energy storage such as batteries as well as household controllable appliances can be regarded as examples of distribution-network-located FERs [5].…”

“…The services include reserves, both spinning and nonspinning, which assist with the efficient operation of transmission networks. The ancillary services can be different depending on the characteristics and types of disturbances occurring in the power system [5], [6]. Currently in Nordic countries, frequency reserve services are categorized into primary reserves named frequency containment reserve (FCR), secondary reserves named automatic frequency restoration reserve (aFRR) and tertiary reserves named manual frequency restoration reserve (mFRR), which are deployed based on the system flexibility requirements.…”

“…Equations (5) and (6) indicate that the charging and discharging power of the BESS cannot exceed their maximum rate, respectively. The binary variable , , in (5) and 6is employed in order to prevent the BESS from being charged and discharged simultaneously. This variable is considered to be 1 when the BESS is in a charging state, otherwise it is equal to 0.…”