SC :MOLS MOLS: Merit-Order-List-Server

Fair competition in ancillary services market

The four German transmission system operators 50Hertz Transmission, Amprion, TransnetBW and TenneT TSO jointly safeguard grid stability. For this purpose they apply ancillary services such as primary, secondary and tertiary reserve energy in order to compensate for frequency variations.

The forecasted demand for tertiary reserve is announced daily on an internet auction platform by the TSOs. The provider with the lowest commodity and capacity prices is awarded a contract and has the legal obligation to hold tertiary power in reserve. The tertiary reserve is recalled according to a Germany-wide merit order list (MOL), which determines the order of the activations from the cheapest to the most expensive providers.

The expansion of renewable energies steadily increases the demand and the operational expenses of the TSOs. It was than attempted to counter the resulting increase in costs by increasing competition in the tertiary reserve power market. For this end, the reserve power market needed to be opened to smaller suppliers and concepts based on “pooling” like virtual power plants. The significant regulatory measures therefore were to lower the minimum bid size and enable providers not only to serve their own control area, but for the whole of Germany.

To enable a tertiary reserve power market across all German control areas with many small providers, the TSOs had to replace the existing telephone call procedure.

On behalf of the four German TSOs, SOPTIM Connect developed a Merit-Order-List-Server (MOLS) for automated and nation wide uniform management of tertiary control power. Providers can communicate with the MOLS using the MeRLin-Client.


Activation of tertiary control on MOLS

The server platform MOLS is operated by Amprion and is made fully and transparently available to all four TSOs. Every TSO can manage recalls and monitor their own tertiary reserve providers. For this purpose, highly specialized dialogue components are used.

The tertiary control power is recalled in quarter-hour increments. Depending on request type, this call is processed from MOLS either event-driven or cyclically in quarter-hour increments. In a first step, the total need is determined across all TSOs. In the second step the provider’s ranking is determined based on the contract data and the current availability of the tertiary reserve power already delivered and any spontaneous cancellations or dropouts.

Suppliers then directly receive activation notifications about the amount and direction (positive or negative), which is then supplied by the providers accordingly. Simultaneously with the activations, the corresponding schedule nominations are generated at the TSO systems and sent out to carry out the matching between the TSOs. In order to assure the the process security, the system monitors all processes on the basis of feedback and confirmation and thus provides a highly automated and very intuitive Cockpit.