The starting point for the intelligent integration of DER units and commercial consumers into a Smart Grid can be seen as the standard for the communication in switch and control gear, IEC 61850. This standard for DER interconnection utilizes TCP/IP as base transmission protocol and was applied for the data and the communication protocol in the E-Energy model region eTelligence.
The overarching goal was to implement a „plug and Play“ ICT concept. This term denotes that the communication technology in a Smart Grid communication infrastructure should be able to adapt to a fluctuating pool of DER units. This objective can be reached by applying the IEC 61850 standard, so that an easy integration of DER units into a Smart Grid or a virtual power plant (VPP) becomes feasible.
The advantage of this norm in comparison to other protocols lies within their comprehensive definitions. The use of this standard was to ensure an improved interoperability between applications of different manufacturers and, thus, to increase the long term investment security, to increase the system security and to enable an efficient data exchange of object oriented data models between technological systems. The multitude of different decentralized energy units that was incorporated in the eTelligence trials can only become controllable by means of a unified standardized data model that is able to describe generation units, storage units and consumption applications as flexibilities.
eTelligence concept for the integration of engine-based cogeneration plants and other generation units based on the IEC 61850 communication standard
Figure 1 exemplifies the concept utilised in the eTelligence trial to integrate an individual engine-based cogeneration plant into a virtual power plant via IEC 61850. In this context, a virtual power plant denotes a bundling of small-sized, decentralised electricity generation units (photovoltaics, biogas units, engine based cogeneration plants etc.) into one assemblage with a common control strategy.
The central task of the virtual power plant lies within the optimisation of the generation capacity in the sense of an orchestration. In order to perform the task, different types of information and prognoses (e.g. price prognoses) are being directed towards the virtual power plants. There, the optimization is calculated and based on the optimisation strategy. Schedules for the individual generation units (“scores”) are being deduced and send to the respective units. Schedules in this context denote data on the planned operation of the units as well as parameters on the potentially available flexibility of the generation capacity. The schedules also constitute the interface between the decentralized generation units and network operators as well as aggregators or virtual power plants.
The model region eTelligence did not only apply the IEC standard 61850 to connect the units between them, but also the Common Information Model (CIM IEC 61970) in order to develop a communication between the market agents (so called eTelligence gateways) and the market place.
The set of standards currently remains unfixed and is still in the development stage. The Common Information Model characterizes the electrical network, the components connected to it, transmission and distribution as well as the relations between the different elements. Just as the consumption applications, generation units are being equipped with energy management equipment in order to be able to receive control signals. The optimised planning and scheduling of the applications and generation units based on different external requirement thus constitutes the overall goal.
In order to be able to easily leverage and market the generation flexibilities on different energy markets, it is necessary to arrive at a standardized display of data and communication on the level of the applications and generation units already.
This task is carried out by the ICT Gateway as an energy management system (EMS). Furthermore, the ICT Gateway plays a decisive role for the integration of different types of units, e.g. for the aggregation function. An homogenous data structure had to be created on the lowest possible level in order to avoid overcomplexities on higher stages in the VPP architecture. The goal was achieved via the implementation of the ICT gateways.
Through the standardised and abstract modelling of the generation units, the goal that consisted in following a „plug and play“strategy in terms of ICT connections was achieved. Once the unit integration has been clearly delineated, the unit control and scheduling can be carried out directly via the automated implementation of the schedules sent out by the control room of the virtual power plant, or indirectly by making use of price incentives that can voluntarily be implemented by the operator of the DER units.
The IEC 61850 standard served to connect 650 Smart Meters, 100 metering sensors in substations, 250 network monitoring sensors at the premises of household customers throughout the field trial of eTelligence. Furthermore, three generation and consumption were connected to a virtual power plant that also included other DER and consumption application via the standard.
The largest part of the sensors delivered metering data on a 15-minute basis in comparison to the previously manual annual meter readings. This equals to a factor of 35.000, so that new data keeping concepts and, thus, IT and software concepts had to be developed and implemented. At the same time, the developed system had to be able to deliver the necessary metering data to the applications in the Smart Grid and virtual power plants with a minimum delay within just seconds. These requirements could be fulfilled by utilising and further developing the IEC 61850 the IEC 61970 standards.
It is comparably easy to develop unit specific profile data, such as e.g. defining the metering and control points (logical nodes) for an upcoming operation of the unit, while utilising the IEC 61850 standards. Especially these profiles became one of the major upgrades to the older approaches derived from the standard with regards to the integration and control of decentralized units and were developed in the eTelligence project. These profiles enabled the project consortium to considerably decrease the individual integration costs for including the units in their overall ICT system. In ideal cases, the integration costs for including a new generation unit were restricted to the reading of the unit profile while setting up the communication to e.g. the virtual power plant. This concept is comparable to Bluetooth profiles of mobile phones, so that it can be deduced that e.g. the integration of an engine-based cogeneration plant into a virtual power plant will become as easy as registering a smartphone to a hands-free car kit in the future. The client can request the IEC 61850 profile of a unit at the server (see figure 1). The unit in fact becomes enables to send their own profile.
The implementation of the standard in form of the eTelligence ICT gateway was so successful that consortium partner EWE decided to develop a product, called the EWE intelligent load manager, from the prototype that is now being offered to operators of decentralized energy generation plants and large commercial consumption application within the service area of the utility.