One of the first responsibilities of a TSO is the maintenance and warranty of the physical balance between electricity generation and consumption in their respective control areas by using balancing energy. Through the coordination of the activation of balancing energy between different control areas substantial potential for efficiency can be exploited.
One opportunity to optimise the activation is to net the demand for balancing energy between several control areas. In mid-May of 2013 such an “Imbalance Netting Cooperation” (INC) has been put successfully into operation between APG and the Slovenian TSO ELES.
Further optimisation is performed within the „International Grid Control Cooperation“ (IGCC) with 9 other European TSOs. APG started its cooperation with the IGCC in April 2014, using a similar model as the INC.
Both cooperations clearly demonstrate the potential of such an optimisation.
Within such Imbalance Netting Cooperations the automatic activation of secondary control energy is optimized through the netting of the balancing demand from the participating control areas, striving for the best possible avoidance of counter activation.
Would one CA require delivery of balancing energy to compensate for a lack of energy, and would at the same time another participating CA require withdrawal of balancing energy to compensate for a surplus of energy, a cross-border optimisation is executed before the activation of national reserves for secondary control.
Since APG is cooperating with the IGCC Austria’s activation of secondary control energy is optimized in two steps. First the netting is performed within the INC with ELES. The residual demand is further optimised within the IGCC (see figure 1).
Figure 1: Principle – Cross-border optimisation through Imbalance Netting Cooperations
The core element of each imbalance netting is the optimisation module, which is used before the activation of secondary control reserves (see figure 2).
The ACE of each participating control area is submitted to the optimisation module, in which the signals are netted in real time, considering provided restrictions (e.g. existing ATCs after intraday gate closure, or manual limitations). As a result of this netting-process, individual correction signals are calculated and submitted to the respective grid control system of each participating control area.
Where a TSO participates in more than one Imbalance Netting Cooperation, the successive residual ACE is submitted to another module, enabling further optimisation in different imbalance netting cooperations.
The optimisation as well as the data submission is performed in an interval of a few seconds.