S1 : in the present status of the electricity market, DER are already able to deliver services to the system

Context

Reliable operation of the power system supposes the implementation of various controls that are often referred to as “system services”. Generally speaking, these services involve Transmission System Operators, Distribution System Operators and service providers.

Challenges

At present, what are the services that can be supplied by Distributed Energy Resources (DER)
in order to increase DER revenue?

Results

The new organisation of the electrical supply industry makes the supply of system services more complex

Fair integration supposes that the grid users contribute to the overall generation – consumption power balance. Simultaneously instruments must exist to avoid unnecessary control efforts. Market architecture proposes different instruments for easily solving these issues. Some of these instruments are market based. Others, due to the specificities of the electrical power system, are activated following technical rules, but resources selection is generally market based.
Balancing is essential for the overall security of the system, but the way it is implemented depends enormously on the context in relation to the real-time system state. In principle, pure market-based instruments are used for quasi steady-state control, while emergency control situations are treated using technical solutions with pre-selected resources (i.e. based on classified bids and offers). Defence actions are based on automatically activated relays.

Balancing active power is currently an accessible service for DER installed in distribution

One single service can be supplied by DER in the present market. It concerns active power balancing activities. This can take two main forms. The first one concerns the self balancing within the aggregator (supplier) perimeter for the sake of the aggregator’s activities, its own benefit and for the benefit of its clients. The second one concerns supplying balancing power to different balancing markets. This service is currently significantly different depending on the market conditions, hence the country under consideration. Market architectures are indeed significantly different throughout Europe. Depending on the access conditions, different possibilities are offered that can even concern system security in emergency conditions, for example “Short-term Operating Reserves (STOR)” in the U.K.

The operational security of the power system depends essentially on adequate system services that must be delivered on time

Transmission System Operators are responsible for the operational security of the system. Generating companies supply balancing services to the system operator following specific contracts. Before the reform of the power industry, balancing activities were organised coherently from quasi steady-state operation up to defence countermeasures. Presently a gap exists between the commercial activities of generating companies and the last resort security countermeasures implemented by TSOs. A reconciliation of commercial and security balancing activities, including demand response, is necessary for increasing system security in emergency conditions.

Power profiles: uncontrolled (red) and controlled (blue) using “Power Matcher” (ECN) as a way for better use of infrastructure, an implicit form of services delivered to the distribution network (see www.powermatcher.net)

Real-time balancing services, based on demand response, must be implemented under

In the present market organisation, demand response contracts are generally activated by electricity suppliers when the system is constrained to sell this power at a higher price on the spot market. However, this implies that these resources will not be available to be activated for security reasons when the state of the system is degrading further. Last resort security should therefore remain close to TSO hands because this measure must avoid conflict of interest for the sake of system security.
Displacing at least a part of the responsibility for system security to generating companies, under a suitable contract with TSOs, is a means to allow the reconciliation of the management of both types of balancing activities: commercial activities and real-time power balancing based on demand response.

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