The large growth in DER presents an opportunity to develop a new approach to black-start; however, there are significant technical, organisational and commercial challenges to address.
Components & enablers
Enablers/requirements:
A minimum load is required when islanding for generators to start safely
- A load bank can provide this in incremental steps
The anchor generator will be required to provide frequency and voltage control, which must be installed / enabled
- A minimum fault level is required for converter connected generation (e. g. wind) to connect. This may not be available when operated as an island; in this case, manufacturers would have to look for alternative means
Main issues identified for islands:
- Low fault level
- Low system inertia
- Voltage control at LV (typically provided by grid transformers)
- High variability of load and generation
State of the art in application and research
Distributed ReStart explores how DER in Great Britain can be used to restore power in the highly unlikely event of a total or partial blackout of the National Electricity Transmission System.
Participants:
- natural gas turbines
- biomass generators
- embedded hydro-power stations
- wind turbines
- solar panels
Methods:
- Restarting an electricity system from a DER, or combination of DERs, from a blackout (without external power supply).
- Maintaining energisation of the newly-created distribution Power Island of aggregated DER and blocks of demand.
- Expanding and synchronising with other Power Islands, energising further generation and establishing a skeleton transmission network.
EASY-RES preserves the long-term grid security, even under very large DRES penetration, by reducing reserve requirements after fault recovery. This is accomplished by introducing fault-ride-through (FRT) capability and coordinated contribution to fault current for each Distributed RES type, in a similar manner to the conventional SGs. Each Distributed RES will contribute to fault currents according to its rated power and relative location to the fault. The aim is to preserve the current level of fault clearing coordination with the existing protection means even under in-creasing Distributed RES penetration.
A main objective of FLEXITRASTRORE is to increase the flexibility of conventional generators by installing novel power system stabilisers, re-storing low rotational system inertia and simulating grid behavior after major events on a representative grid model, which will allow better insight into grid dynamics and stability.
A number of projects (STORY, TILOS, The Smart Grid Battery Storage Project Prottes, WiseGRID) are focusing on the storage challenges of black start on generation.
Technology Readiness Level
TRL 3
It is envisaged that the Distributed ReStart project will demonstrate a world first – coordinating bottom up from distribution networks to trans-mission level to provide a safe and effective Black Start service. The project is currently at the initial phase, with key concepts having been developed.
Technology: TRL 4 – 8 – Research, Development, Demonstration and Implementation
Distributed ReStart focuses on technology that has already reached TRL 4 – 8 for providing black start services.
Battery + Generation: TRL 7 – Demonstration
Flexitranstore demonstrates how a new, large-scale battery energy storage system connected to conventional generation can help provide black-start.
Current focus of R&D and research gaps
Distributed ReStart is currently in its early phase, but is researching both technical feasibility and the coordination between TSO / DSO / other agents in the event the solution is necessary, as well as the regulatory framework.
References
[1] Distributed ReStart [Link1] [Link2] [Link3]
[2] Flexitranstore, demo 7 [Link]
[3] EASY-RES [Link]
[4] FLEXITRASTRORE [Link]
[5] STORENET [Link]
[6] STORY [Link]
[7] WiseGRID [Link]
[8] UPGRID [Link]
[9] TILOS [Link]
[10] CROSSBOW [Link]
[11] The Smart Grid Battery Storage Project Prottes [Link]
[12] VINPOWER [Link]