The use cases presented here constitute examples of the information flows expected to be exchanged between the different entities defined earlier, once again considering the aforementioned short-term in-tegration. It should be noted, however, that the presented sequence diagrams for each use-case are
simplified. The expected information exchange in each use case is very likely to be far more complex.
Nonetheless, it intends to represent the dynamics involved in an integrated technical and market op-eration. It is also important to notice that some of the information flows represented in the sequence diagrams may not occur sequentially in the sense that some of them may take place in parallel, in case the communications infrastructure or the involved entities allow it. The sequence of notifications can vary when considering different scopes and operating conditions.
From the use cases considered within this scope of section only two of them will be presented to avoid an unnecessarily heavy description: the normal and emergency. Appendix B presents the simplified market negotiation case, with the day-ahead and intra-day negotiations, along with the overall use-case, where a transition over all of different states of the functional and operational model defined previously.
For simplicity, in all sequence diagrams, only one EB entity is considered representing generically the different versions of the EBs, namely those concerning the MV and LV customers. The differentiation will be pointed out in the message exchange description. In the normal operation a market oriented information exchange is illustrated where it is assumed that a successful day-ahead negotiation scheme was already carried out in the previous day and a snapshot of the implementation is presented.
Market Agg RAU MGAU EB DMS CAMC MGCC
(1) Periodic Report (2) Market Periodic Report
(3) Technical Periodic Report (4) Set-Point
(5) Set-Points (6) Report Request
(7) Report Request (8) Report Response (9) Report Response
(10) Set-Point
(11) Set-Point
Figure 3.5: Normal Operation State
The information exchange concerning the normal operation is depicted in Fig. 3.5 with the following sequence:
1. The EB issues a periodic report to the MGAU;
2. The MGAU forwards market related information from the received periodic report to a specific aggregator;
3. The technical related periodic report information is forward from the MGAU to the MGCC;
4. The aggregator issues market negotiated set-points to their LV customers through the MGAU;
5. The MGAU forwards the set-points to the respective EBs;
6. A report request is issued (asynchronously) by the aggregator to one or more MV customers via RAU. This report can be due to changes in the operation conditions when compared to the forecast made by the aggregator for the current day. Aggregators can adjust their operation according to the contracted conditions established with their customers in order to ensure that the market conditions negotiated also with the DSO in the previous day are kept; otherwise they may incur in penalties;
7. The RAU forwards the report request;
8. The target EB-MV issues a report response to their aggregator through the RAU;
9. The RAU forwards the report response to the respective aggregator;
10. The aggregator issues one or more set-points to their MV customers according to the received report information;
11. The RAU forwards the set-points to the respective MV customers.
In emergency operation the market information exchange is suspended due to a disturbance event with a significant impact on the electric grid operation, making it unfeasible to address such event in market conditions. The impossibility of ensuring market operation can be due to several reasons, such as a significant deviation of the negotiated conditions in the previous day or a violation of a technical restriction endangering the security of the distribution operation. This state assumes that no intra-day market negotiation solution can feasibly handle the disturbance, which means that the involved technical operation entities are called upon to secure the system operation.
The information exchange concerning the emergency operation is depicted in Fig. 3.6, where the following sequence is considered:
1. A disturbance is detected in a multi-microgrid level and the CAMC is aware of the fault occurrence.
The CAMC informs the DMS of the occurrence of the fault which can have impact beyond the affected MG, although in this example it is assumed that the disturbance impacts the MV level;
2. The CAMC informs the affected MGs managing entities, that is, the MGCCs, of the disturbance.
This message can also convey set-points for MGCCs in order to immediately handle the consequences of the disturbance in the LV operation;
3. The CAMC informs the MV EBs of the disturbance via RAU. This may also include set-point for EBs to participate in mitigating the impacts of the disturbance event;
4. The RAU forwards to EB-MVs the disturbance detection information, along with potential imme-diate set-points;
5. The RAU informs the affected aggregators of the temporary suspension of market operation while the emergency operation is active;
Market Agg RAU MGAU EB DMS CAMC MGCC
(1) Disturbance Detection
(2) Disturbance Detection (3) Disturbance Detection
(4) Disturbance Detection (5) Market Suspension
(6) Set-Point
(7) Set-Point (8) Set-Point
(9) Report Request (10) Report Request
(11) Report Response
(12) Report Response (13) Report Request
(14) Report Response
Figure 3.6: Emergency Operation State
6. A set-point is issued by the CAMC to target MV EBs to deal with the disturbance, via the RAU;
7. The CAMC issues a set-point to target MGCCs to handle the disturbance;
8. Each MGCC will assess the requested set-points from CAMC and, after running a local control algorithm, will issue set-points to the LV EBs under its supervision;
9. The CAMC issues a report request to involved MGCCs to assess the state of the system after the set-point exchange process is disseminated;
10. The MGCC in turn issues a report request to the LV EBs under its supervision to update the information to report back to the CAMC;
11. The target LV EBs report back to the managing MGCC;
12. The target MGCCs report back to the CAMC issuing the report request;
13. The CAMC issues a similar report request to the MV EBs under its supervision;
14. The contacted MV EBs report back to the CAMC and a new set-point exchange sequence can be initiated to ensure the necessary actions towards the restoration of the normal operation state.