Ancillary Services Offered by Distributed Renewable Energy Sources at the Distribution Grid Level: An Attempt at Proper Definition and Quantification

Abstract

The gradual displacement of synchronous generators driven by conventional power plants, due to the increasing penetration of distributed renewable energy sources (DRES) in distribution grids, is creating a shortage of crucial ancillary services (AS) which are vital for the frequency and voltage stability of the grid. These AS, and some new ones, could now be offered by the DRES, particularly those that are converter interfaced, in a coordinated way in order to preserve the grid stability and resilience. Although recent standards and grid codes specify that the DRES exhibit some system support functions, there are no specifications on how to measure and quantify (M & Q) them both at DRES level and in aggregated form. The M & Q of AS is crucial, since it would allow the AS to be treated as tradable AS in the current and future AS markets. This paper attempts to define a number of AS that can be offered by converter-interfaced DRES and suggests methods for their M & Q. The new AS addressed are: (1) inertial response; (2) primary frequency response; (3) active power smoothing (ramp-rate limitation); (4) exchange of reactive power for voltage regulation; (5) fault-ride-through (FRT) and contribution to fault clearing; (6) voltage harmonic mitigation. Additionally, a rough estimation of the additional investment and operational cost, as well as the financial benefits associated with each AS is provided in order to form the basis for the development of business models around each AS in the near future.

Ramp-Rate Control of DRES employing Supercapacitors in Distribution Systems

“…The studied topology is a real testbed in the University of Sevilla (Fig. 1) developed in the framework of H2020 Project EASY-RES, [17]. Its main components are: (i) A 20 kVA three-phase three-wire VSC with V rated DC =750V and V rated AC =400V; (ii) An SC of 6 F/160 V, [18], with maximum instantaneous power of 2kW; The total SC energy is 21.33Wh, however, due to the SC safety voltage limits recommended by the manufacturer, the total SC energy used for RRL control is equal to 9.33Wh; (iii) A controllable DC current source.…”

Review of Stationary Energy Storage Systems Applications, Their Placement, and Techno-Economic Potential

“…With regard to the question of who the AS RES providers are, it can be stated that the AS are generally supplied by thirdparty providers, but also in part by the transmission system operators (TSO) and distribution system operators (DSO) themselves [17]. Regarding the classification in Table 1, however, it can probably be stated that the utilities at the mediumvoltage (MV) and high-voltage (HV) level will remain the operators here.…”

Characterization of TSO and DSO Grid System Services and TSO-DSO Basic Coordination Mechanisms in the Current Decarbonization Context

“…Traditional grid services for TSOs are for example reviewed in [9]. The work in [10] characterizes new DSO services, and makes an attempt to assess the amount of AS that distributed resources could provide to both TSOs and DSOs. Integration of DER to provide existing TSO ASs and investigation of new DSO local system services is also addressed in [11], where market designs for DER integration are also discussed.…”

“…Considering the size and capacity of the system 9. Locally, CM can solve problems on feeders, transformers or PCC, while it can also be considered for whole LV grids, overlaying MV feeders and even at HV level 10. Substation, feeder, transformer or PCC 11.…”