Rationale for Information Segregation

There are a number of reasons that justify the separation of the technical and market information flows, which can be associated with the evolution of the logic model. One of them has to do with the fact that the exchanged information has clear different scopes, since it concerns on one hand market participants and on the other the system operator entities pertaining to the hierarchical control structure. Another

reason can be found on the different requirements that both information flows have, namely in terms of latency, reliability and bandwidth. These communications requirements have obvious implications both in architectural and technological aspects that have to be considered when designing and implementing communications solutions capable of meeting the desired QoS indices.

Although it is admissible that on the short term the communications infrastructure of the system operator is available for the exchange of information related with market operation, it is not expected a particular interest by the DSO to keep ensuring this connectivity. Furthermore, significant investment could be necessary for its communications infrastructure to handle the expected increase of traffic due to the connection of electric vehicles to information networks. Unless there is an economical incentive or a regulatory enforcement, the DSO is not likely to over-invest and maintain a communications network to support the exchange of information that in the long term will potentially be outside its typical business model. There are also different expectations that DSOs put on the communications infrastructures that needs to be considered. At present the technical operation requirements in terms of communications for the electric distribution network are still limited. In fact, communications systems are being deployed for applications such as smart metering and raw management and control, with specific technologies and architectures being selected for that purpose.

It is reasonable to expect that, unless any legal or regulatory policy is set, the commercial representa-tive, in the figure of the aggregator, becomes responsible for ensuring the necessary connectivity with its represented customers, through their EBs. When considering the data volumes that will be associated with market information flows and the non-real-time characteristics associated with this information ex-change, one finds that the requirements are not significantly different from those of other communications services currently supported by telecommunications operators using broadband networks to provide for instance Internet services. Hence, it seems reasonable to consider that the participation of customers in the market environment through their aggregators, as commercial representatives, can be performed using the same Internet based solutions as those provided by telecommunications operators. Since market information exchanged between the customer and the aggregator does not directly concern the operation of distribution system, it is admissible that the customer provides the necessary communications access in order to exchange information with a market representative namely through ADSL, coax cable, fiber or a similar Internet access solution. Such vision does not seem to collide with service access already found in other cases where the customer uses an Internet access service to manually report electric metering information to the service provider or access other types of services like e-banking.

Similarly, it is up to the DSO to implement a communications infrastructure that ensures the necessary requirements for the advanced control strategies under the smart grid paradigm providing high reliability indices and reduced latency for real-time or near real-time services. This will allow the DSO to protect its most important asset, which is the distribution network, by implementing the necessary management and control strategies along with the required security schemes. It will also allow the DSO ensuring that in case of a sporadic emergency event that leads to market operation suspension, the communications infrastructure is able to support the necessary recovery strategies that allows a fast transition to the normal state. The information segregation is also advocated in reference models like those defined by NIST or SGAM, which were presented previously, where some exchange of information between domains are considered to be made through public Internet networks.

3.4 Entities

The entities previously considered in short and long term perspectives are distributed over three domains, which are aligned with those also defined in the NIST model: Operations (Technical Operation), Markets (Market Operation) and Customer.

The entities defined under the technical operation scope pertain to the distribution system operation under a hierarchical architecture based on the MG and MMG concepts:

ˆ DMS - Centralized management entity that incorporates a SCADA system enabling automatic and manual operation and control over the entities below. It is also the head of the interaction of the system operator with the market operation;

ˆ CAMC - Heads the management and control of MV distribution network elements like DERs, controllable loads, medium voltage EBs and MGs through their MGCCs;

ˆ MGCC - Controls and manages the controllable devices connected to the LV distribution network, among which are low voltage EBs.

For the customer operation domain, the considered entities are mainly energy boxes, which can be regarded as local energy management systems derived from smart metering infrastructures; they can be divided in two categories:

ˆ EB MV - medium voltage energy box, which intermediates system monitoring and control requests, usually between CAMCs and local controllers and monitoring devices. It will also interact with market representatives, directly or through a service based entity provided by the serving utility.

Among the local controllers managed by these EBs is the Cluster Vehicle Controllers (CVC), which are responsible for managing and controlling groups of EVs, like in fleet management systems, parking lots or in public charging systems.

ˆ EB LV - low voltage energy box that acts as a domestic gateway conveying the necessary monitoring and control data, usually to an MGCC or a concentration unit, from local metering and control devices. It will also interact with market representatives, directly or through a service based entity provided by the serving utility. Among the available local controllers, the Vehicle Controller (VC) is highlighted due to the set of functionalities it implements to allow the management and control of the connected electric vehicle.

In the market domain the key element in the defined architecture is the aggregator, which is a commercial representative of a group of customers. It can also be regarded as a representative of groups of specific controllable devices, which is the case of EVs. These entities are responsible for market operations, like supply and demand offers, and the necessary acquisition of information from their customers, so that their forecasting tools can allow an enhanced participation in the market. Depending on the model, they can directly exchange information with customers or may use utility communications infrastructure to convey that data. As such, within the technical operation domain there are entities that ensure that market information is securely exchanged between aggregators and end customers:

ˆ RAU - represents the regional aggregation level of customers that include industrial, commercial and other MV customers that have a significant impact on the MV distribution network; it is responsible for conveying market information between EBs and the commercial representative;

ˆ MGAU - represents the microgrid aggregation level of customers and is responsible for the market related data exchanged between LV EBs and the commercial representative.