Much has been said about subsidies and their calculations that each agent makes to arguments for and against MMGD (micro and mini distributed generation). ANEEL ( 50/22) from Law 14300/22 established the calculation of GD (distributed generation) subsidies, which is the reference for the value posted on its website under the title “Subsidiometer”.
The calculation is made based on the total energy injected, where microgeneration must pay for Wire B (transition until 2029) and minigeneration for Wire B plus 40% of Wire A. From a more careful analysis, it is possible to see that there are flaws in these numbers.
The first caveat is that the subsidy cannot be generalized because each region and concession has different dynamics and characteristics. The simple fact of considering the entire B Wire, which represents the entire distribution network, regardless of where the injection is, is already a mistake.
To better understand, let's reduce this generalization a little and use the simplified single-line diagram by voltage level, widely used in distributors' tariff review processes.
The Figure shows four basic voltage levels that represent Wire B: high voltage (AT-2 and AT-3), medium voltage (MT) and low voltage (BT), in addition to the basic transmission network treated as Wire A.
These levels are connected through transformers such as those that connect high (138 kV) with medium (13,8 kV), AT-2/MT (blue).
Traditionally, the flows in these transformers have a single direction from the basic network to consumers at each voltage level.
In this way, a residential consumer, connected to 220 V, uses all voltage levels and pays for all of them, that is, Wire A and Wire B.
The entry of DG disrupted this environment of unidirectional flows, mainly in MV and LV networks.
When analyzing the area of influence of the micro DG connected to the LV, it can be seen that if there is no flow inversion in the MV/LV transformer (black), the DG only uses the LV network and should only pay for this network.
Since MT and BT assets represent on average 80% of the distributor's costs, we could say that these agents should pay only 40% of Wire B.
For mini DG in MV, if there is no flow inversion in the AT/MV transformer (blue), it should only pay for the MV and LV network, that is, 80% of Wire B. In this case, it clearly would not pay for the 40% of the Basic Network.
If there is a flow inversion, payment should be made up to the level at which the inversion is completed. For example, the payment for Wire B plus the portion of Wire A should only be paid by the mini DG if it brings about a flow inversion at the border transformer (green) with the Basic Grid.
This premise is already used today in the locational TUSDg tariff for injection into the 138 and 88 kV networks. It can be seen that the flow inversion problem ends up being a tariff problem and not a technical one.
This simplistic analysis already denotes a certain caution in the use of these numbers for reimbursement by the CDE, for the establishment of public policies and future regulations.
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The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.
