ICT Reference Architecture Design based on ... - IEEE Xplore

ICT Reference Architecture Design based on Requirements for Future Energy Marketplaces C. Wietfeld, C. M¨uller and J. Schmutzler

S. Fries, A. Heidenreich and H.-J. Hof

Dortmund University of Technology Siemens AG Communications Networks Institute (CNI) Corporate Research and Technologies Dortmund, Germany Munich, Germany Email: {christian5.mueller, jens.schmutzler, christian.wietfeld} Email: {steffen.fries, alla.heidenreich, hans-joachim.hof} @tu-dortmund.de @siemens.com

Abstract—Today’s Smart Grid initiatives propose highly decentralized power supplies with an increased number of providers utilizing renewable energy resources. This idea is driven by the imminent requirement for improved sustainability of power industries and also by the legislative demand for more competitive energy market structures. Due to these intentions the number of regional market participants will be increasing dramatically over the next few years. In order to coordinate and balance energy supply and demand under these new circumstances, major ICT related challenges need to be addressed. This paper introduces a reference architecture design offering a set of extensibility points to existing solutions for increased flexibility in moving energy markets. The architecture design is based on the idea for open energy marketplaces in regional power distribution networks enabling load management and transfer. By defining flexible high level interfaces, it respects potentially upcoming requirements, new evolving services, and - resulting from these services integration and mediation of future market roles. Furthermore the architecture presented in this paper also considers various regulative requirements resulting in different operational modes for provisioning of clearing, monitoring and controlling data.

I. I NTRODUCTION Today’s electric power distribution systems are on the move to smarter grid infrastructures, accompanied by complete restructuring of the conventional roles on energy markets. The classical system architecture of the electric power grid defines distinct roles for energy producers, -suppliers and -consumers. With the new paradigm of Smart Grids driving towards sustainability, some of these market roles are redefined. The energy supplier systems have to handle an increasing amount of energy gained from renewable energy sources and household energy production systems. These forms of energy are produced in a much more decentralized way and also have a much more volatile characteristic compared to traditional forms of energy provided by current energy producers. At the same time one of the key factors for efficient and economic power generation is a balanced load level on power plants. Both aspects directly influence the distribution process of transport and distribution system operators and require the adoption of advanced Information and Communication Technologies (ICT) in these processes. The role of classical consumers also changes from pure

consumers to more complex customers called prosumers1 . The prosumer now has the ability to produce energy with his own generators and feed it back into the grid. By enabling smart metering at the prosumer’s site and providing different tariff models with load level aware price incentives, the prosumer is actively involved in the energy trading market and most importantly becomes more aware of his power consumption levels. In order to avoid this new market involvement being interpreted as an additional burden for the prosumer, autonomous managing agents and remote controlling agents play a key role in this regard. For this purpose the prosumer needs transparent and bidirectional connectivity to the energy marketplace. This comes along with an increased demand on data rates, Qualityof-Service (QoS) and security measures with respect to the underlying ICT architecture. The work in this paper concentrates on the design of an ICT reference architecture for regional energy marketplaces. It considers previously mentioned requirements for ecologically as well as economically sustainable energy supplies. The work was conducted as part of the E-DeMa project[1]. E-DeMa is one of six projects funded by the German Federal Ministry of Economics and Technologies (BMWi) in the national joint research initiative E-Energy. This initiative aims at supporting research projects practically demonstrating future power grids in six distinct regions throughout Germany. E-DeMa focuses on a regional energy marketplace deployment in North RhineWestphalia, Germany’s most densely populated federal state. The following section introduces related work in standardization and the methodology applied during the design phase of the reference architecture. Section III characterizes in more detail the requirements being addressed and satisfied by the architecture design. In section IV all currently respected market roles and interfaces are described in detail. The architecture’s potential in extensibility and adaptability regarding new market roles and upcoming services for Smart Grids are addressed in section V. It especially focusses on extensibility points for integration of Electric Vehicles (EVs) as part of the national development plan for electric mobility. Finally the paper closes with conclusions and an outlook on future work. 1 producer

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II. R ELATED WORK AND METHODOLOGY Several approaches for interoperable communication system infrastructures for future energy grids are presented in literature [2][3][4][5]. Interoperability between different technologies and architectures regarding energy distribution and ICT is the driver for defining reference architectures resulting in abstract component descriptions and information exchange patterns, like currently developed in [2]. An overview of the current status of standardization is given in [3]. The reference architecture presented in [4] and [5] describes an abstract system architecture being the basis for subsequent detailed system specification. The presented approach is based on international standards, like IEC 61968/61970 [6][7] and IEC 61850 [8] offering reliable concepts for management and automation functionality. A reference architecture for object models, services, configuration languages and protocols has been established by the IEC TC 57 [9]. They associated and consolidated different standardization efforts in order to define a Seamless Integration Architecture. One result of this work is the IEC 61850 standard providing a framework for energy automation. An adjacent standard - IEC 62351 [10] - targets dedicated security requirements and provides security solutions for this application domain. The architecture presented in this paper is derived by a technology-independent and requirement-driven approach. Therefore an in-depth requirements analysis on the communication interfaces and their information exchange patterns was conducted. This strategy enables selection of suitable technologies for different interfaces and a reliable system design. Besides the exchange of management and automation information, tariff and measurement information are communicated. The latter have different needs in terms of reliability, latency, data rate, but also regarding their security requirements e.g. confidentiality or non-repudiation. III. R EQUIREMENTS Requirements summarized in this section combine different groups of requirements concerning the infrastructure, system and general aspects. As a general requirement the infrastructure has to provide capabilities for supporting decentralized management and control functionality for a Smart Grid. Additional resources regarding the ICT infrastructure are required for the integration and consideration of the customers’ components via local ICT Home Area Network (HAN) Gateways. Interoperability between a wide spectrum of communication technologies and protocols is supported by using open and free-licensed application protocols in conjunction with an IP based technology. The underlying trust model for energy automation networks, as it exists today, is changed by the introduction of new participants. Therefore, security aspects regarding authentication, access control, integrity, and privacy are a cornerstone of the resulting architecture supporting legal and business needs [11][12][13]. Figure 1 shows the differences in terms of security between IT & communication networks and electricity control networks.

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Security requirements analysis for IT and energy control networks

The requirements for the system architecture with respect to the particular interfaces between the involved components are based on the following categories: • • • • •

Quality of Service Communication requirements Data volume and timing restrictions Prioritization Security

The following section explains the architecture in more detail building upon requirements from each category. IV. ICT R EFERENCE A RCHITECTURE D ESIGN The reference architecture shown in Figure 2 adopts architectural concepts of related architectures and adds several enhancements to these approaches with respect to related requirements described in section III. The purpose of the abstract description of the architecture is caused by defining clear reference points between particular components in order to identify information exchange together with the involved interfaces, e.g. between the HAN Gateways and energy marketplaces, in order to specify appropriate ICT technologies. The presented architecture is driven by two components, regional energy marketplaces and local HAN Gateways in each household. A. Regional Energy Marketplaces The central element of future energy systems is based on regional energy markets enabling the prosumers to manage their contracts, use advanced services of third-party service providers and trade their energy consumption and generation contracts. Each energy marketplace is operated and maintained by the marketplace operator. Due to the interdependencies (e.g. in terms of balancing power) of multiple regional marketplaces, each managed by its own regional operator, interoperability between these platforms is one of the core requirements on the marketplace design. Therefore, these interfaces are designed to support typical standards of the application domain, which often stem from ISO/IEC. But also standards from the more typical Internet domain are applied like XML or TLS.

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Fig. 2.

ICT Reference Architecture Design

B. Local HAN ICT Gateways In order to ensure transparent connectivity to all inhouse components, the comprehensive introduction of HAN Gateways is one of the central elements for combining the high demands on security and providing an extensive connectivity to the prosumers’ household. On the one hand the gateways act as firewalls, on the other hand the gateways provide connectivity to the HAN entities. Thereby two different forms of HAN Gateway can be considered: • Metering HAN Gateways • Management HAN Gateways The Metering HAN Gateways collect and store metering data from several metering devices, like electricity, gas, water and heating meters. The collected data is securely transmitted bundled to the meter reading operator. Security in this context comprises two services: Integrity protection and non-repudiation for metering data, which is often done using digital signatures allowing the meter reading operator to validate that the metering data has not been altered by an intermediate component. Furthermore, the bundled transfer may be encrypted to ensure the privacy of user related data in environments, were physical access to the transmission path cannot be secured. Moreover, a local feedback system gives the prosumer transparent insight into his current energy consumption. In conjunction with available tariff information motivation for reducing overall power consumption can be achieved. The Management HAN Gateway, which can be realized as an integrated HAN Gateway or as a separate hardware component, presents an enhancement of the metering HAN Gateway and offers management functionality to the prosumer’s HAN entities. The energy management can be done either through the prosumer itself, motivated by tariff or through the Distribution System Operator (DSO) for controlled or emergency load reductions. Therefore interfaces to the prosumers’ appliances,

loads and local power generation components are provided. Depending on an external pricing information several loads can be controlled, e.g. charging of EVs as well as controlling home heating system. For example an intelligent washing machine makes use of the dynamic tariff information by starting the washing procedure in low tariff periods and avoids starting it in high level tariff periods. In addition to this, the connection interface can be used for maintenance, remote configuration issues and firmware updates. One of the key capabilities is the integration of decentralized power generation systems, which will make up a large part of the energy generation of future systems. Nowadays an increase in local power generation installation can be observed, e.g. solar panels, wind power plants and combined heat and power generation. A central controlled energetic recovery system is necessary to meet the requirements of the energy grid quality management. Referring to the communication market a dedicated infrastructure has to be provided by an operator, that is also providing management and installation services to the prosumers. In order to maintain a reliable ICT infrastructure between the HAN Gateways and the marketplace, a HAN Gateway Operator provides reliable ICT components for software updates, administration and configuration issues. This operational tasks can be combined and covered by one of the participants on the marketplace, which is described in the operational scenarios in section V. C. Marketplace Participants and Interfaces The infrastructure components consist of the following B2B-Systems interacting with the prosumers’ equipment and other components via the marketplace platform: • Meter Reading/Using Operator (MRO/MUO) • Distribution System Operator (DSO) • Transmission System Operator (TSO) • Energy Service Provider (ESP)

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Electric Utility (EU) Appliance Service Provider (ASP) • Aggregator (AGG) In order to limit the number of interfaces between these participants, multiple interfaces between groups of components are combined together, e.g. interfaces between meter and HAN Gateway are combined with one single interface IF1.N and interfaces between local systems and the HAN Gateway are labelled with IF7.N. The system specification builds upon these groups of interfaces and specifies the necessary subsets of the interfaces for each component individually. Multiple access technologies are possible in order to ensure • •

Interface IF 1.N IF 2.N IF 3.N IF 4.N IF 5.N IF 6.N IF 7.N IF 8.N IF 9.N IF 10.N

Description Metering Interfaces Administrative Interfaces Marketplace Interfaces (Future Usage) Service Interfaces (HAN Gateways) Inter-HAN Gateway Interfaces Service Interfaces (E-Energy Marketplace) Interfaces between HAN-Gateways and manageable prosumers’ loads User Interfaces (HAN-Gateway) HAN Gateway Interface for the E-Energy Marketplace User Interfaces (E-Energy Marketplace)

TABLE I T EN S YSTEM I NTERFACES /G ROUPS OF I NTERFACES

communication between infrastructures on the prosumers’ and backbone’s side. On the one hand dedicated infrastructures ensure high quality of service due to an exclusive use (e.g. broadband PLC infrastructure[14]). On the other hand shared public access technologies (e.g. GPRS or DSL) offer more cost-efficient solutions. Consequently, investigations on highly reliable and secure communications in large scale scenarios are the main focus of the research program in the E-DeMa project. V. E XTENSION P OINTS AND A DAPTABILITY Potential extensions of the architecture are addressed in the following section especially focusing on operational modes of the ICT infrastructure and the integration of EVs as part of the national development plan for electric mobility. A. Modes of Operation Mode of Operation 1 IF 6.0 / IF 6.1

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The reference architecture presented in the previous section introduced the framework for interconnecting different

systems. More concrete modes of operation are presented in this section. Three modes are illustrated in this work which combine various components of the reference architecture differently: 1) Mode 1 - Joint HAN Gateway Operator: In this mode, only one HAN Gateway exists. The HAN Gateway Operator and the Meter Reading Operator are the same instance, which ensures the operational infrastructure between HAN Gateway and the remaining service infrastructure. Additionally this joint function is responsible for the maintenance and engineering of the HAN Gateway. Figure 3 shows the mode of operation scenario 1, which results from combining the role of the HAN Gateway Operator and the Meter Reading Operator. The gateway gets installed, configured and administrated by the HAN Gateway Operator. The acquisition of measurement data is done through a dedicated infrastructure, which is provided by the HAN Gateway Operator. Direct access is not provided to third party service providers, which have to communicate through a portal/Web Service API of the HAN Gateway Operator. 2) Mode 2 - Separated HAN Gateway Operator: In mode 2, shown in Figure 3, also only one HAN Gateway exists. But this mode explicitly separates the HAN Gateway Operator and Meter Reading Operator. An independent HAN Gateway Operator is responsible for the operational communication infrastructure between the consumers’ gateways and the remaining service infrastructure, especially to the Meter Reading Operator. This also includes maintenance and engineering of the HAN Gateway. The gateway is installed, configured and administrated by the HAN Gateway Operator. All other service operators and the user himself are allowed to install certified applications directly on the gateway. 3) Mode 3 - Split HAN Gateway: The HAN Gateway is split into two physical entities, the Metering HAN Gateway maintained by the HAN Gateway Operator and the Management HAN Gateway maintained by the customer himself. The metering gateway is installed, configured and administrated by the HAN Gateway Operator. The user is responsible for all applications on this gateway, which can be realized by two different ways: • The user is allowed to install certified applications directly on the gateway. • The user is allowed to install any kind of applications directly on the gateway. By using this operational scenario, which is shown in Figure 3, both gateways are separated and only linked by interface IF5, which is used for administrative purposes on the Management HAN Gateway and for transmission of power consumption data to the user interaction system. Note, that the gateways may be virtually separated or physically separated, but it is more likely that there will be two distinct physical devices. B. Extensibility Points - Electric Mobility As described in previous sections, the energy marketplace defined in E-DeMa consolidates all transactional information sources. It is therefore the central ICT anchor point for future

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extensions. This includes both infrastructural additions for power delivery, as well as new actors offering value-added services to other participants of the E-DeMa marketplace and therefore becoming part of the value chain. In this section we are taking a look at integrating electric mobility into the energy marketplace considering its special requirements. Other potential areas of interest could be applications for smart home integration and industrial automation in order to lower overall power consumption levels. 1) Use Cases and Requirements in Electric Mobility: Electric mobility has some special requirements compared to traditional eletric consumers which have to be considered. Due to the mobility of the EV a customer’s energy consumption cannot be determined by stationary meter readings at the customers site. The power demand for charging the EV is consumed along the owner’s mobility path. Hence the user’s meter readings together with his contract credentials have to be communicated from the Electric Vehicle Supply Equipment (EVSE) to the respective Mobility Service Provider (MSP). This includes both accounting information as well as authorization for gaining access to the charging infrastructure. Additionally roaming between different EVSE Operators (EVSEO) needs to be considered. In order to allow for seamless charging processes independent of the underlying infrastructure providers, the previously introduced E-DeMa marketplace has to be extended by certain participants. These new participants are described in more detail in the following section. The mobility management is detailed in section V-B3. 2) New Actors in Electric Mobility & E-DeMa Integration: The following new actors are complementing the participants of the energy marketplace as described in section IV-C: • Mobility Service Providers (MSPs) • EVSE Operators (EVSEOs) • E-Mobility Hub (EM-Hub) • Demand Clearing Houses (DCH) The Mobility Service Provider is the contract counterpart of the customer. The customer always closes a contract with a MSP and uses its tariffs and services for charging an EV. The EVSE Operators are responsible for the operation and maintenance of their charging infrastructure. The EVSEO provides energy to the customer in (semi-)public places. The EM-Hub is an MSP independent instance which enables roaming between different EVSEOs. It provides authorization means and forwards the charge detail records to the corresponding MSPs for accounting purposes. The Demand Clearing Houses are responsible for balancing power and load levelling of the underlying charging infrastructure, e.g., the load of the entire region of a local network station. The DCHs might be hierarchically organized corresponding to different energy grid levels. Figure 4 illustrates how the previously described, new participants from the electric mobility domain are integrated into the E-DeMa marketplace, how they interact with each other and with traditional energy market participants. The extension respects charging scenarios in both public and private parking spaces. In the latter case the EVSE is part

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Electric Mobility Extensions

of the customer’s HAN and communication to the marketplace is not directly established by the EVSE but through the HAN Gateway. This allows to keep complexity of private EVSEs at a minimum and reduces costly link redundancies. 3) Electric Vehicle Mobility Management: The management of inter-market transactions for charging processes of EVs is inspired by the roaming approach already known from mobile communication infrastructures. Roaming for users of EVs is provided by two new virtual entities: • Home Location Marketplace (HLM) • Visited Location Marketplace (VLM) Both entities are present in every clearing house for accounting purposes of each energy marketplace. The HLM represents the regional energy marketplace where the customer registered the EV. In most cases this marketplace should be equivalent to the market where the household of the customer is registered to. The VLM represents the energy marketplace, the customer is joining by plugging in his EV in the infrastructural domain of a marketplace different from his HLM. During the authentication process the EV communicates its corresponding HLM through the vehicle-to-grid communication interface to the VLM. The VLM now requests synchronously all relevant information from the HLM in order provide access to the power grid for the customer. After the charging process the VLM reports all necessary accounting information to the MSP residing at the HLM asynchronously. Similar to mobile communications the VLM might also account for roaming fees if applicable. In contrast to the mobile communication architecture it is expected that from a security point of view the underlying architecture will make use of certificates and digital signatures to ensure integrity and non-repudiation for energy offers and concluded charging contracts which serve as the base for accounting and billing. Moreover this technology is expected to be applied to further vehicle related services like software updates or remote maintenance.

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C. Security Management In order to provide an enhanced security management a dedicated entity responsible for authentication and authorization to realize access control has to be implemented. Moreover, this entity provides means to ensure reachability of the HAN Gateway, even if it is located behind Firewalls or Network Address Translation (NAT) devices. This is especially important, if an existing infrastructure is being enhanced with energy control services targeting not only the communication of metering information to a central entity, but also active control options for the DSO in order to ensure stability in the distribution network. The entity realizes this by invoking dedicated communication sessions at the HAN Gateway through the DSO. It is called ASIA - Authentication, Session Invocation, and Authorization - reflecting its core functionality. ASIA enhances the architecture as depicted in Figure 5. Note, Infrastructure IA AS

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Fig. 5. Automated Key management using ASIA function - Authentication, Session Invocation and Authorization

that the ASIA functionality may be provided as a separate component or may also collapse with existing roles of the architecture, like the HAN Gateway Operator or the Meter Reading Operator. VI. C ONCLUSION AND O UTLOOK The proposed reference architecture design represents the architectural concepts for high level interaction between particular entities of the ICT infrastructure of future energy grids. The requirements and definition of interfaces towards the regional energy marketplace have been discussed by a technology independent approach. Extension points as well as adaptability of the presented concept have been presented by discussing several modes of operation and the integration of electric mobility components. Especially from the viewpoint of security several enhancements have been proposed targeting a dedicated function responsible for authentication and authorization to realize access control. The subsequent project phase of the E-DeMa project focuses on system specification for realizing the components according to the defined requirements and adopting stateof-the-art technologies for interfacing these components. A detailed evaluation of the system design is targeted by labtesting and field-testing with more than 1000 HAN Gateways in two separate model regions. Large-scale issues of the ICT infrastructure are investigated by modeling the architecture

in an event-driven simulation environment in order to allow for performance analysis’ as well as protocol and technology optimizations for the proposed system design. VII. ACKNOWLEDGEMENT The work in this paper was partially funded by the German Federal Ministry of Economics and Technology (BMWi) through the project E-DeMa with reference number 01ME08019A. The authors would like to thank the project partners RWE, Miele, ProSyst, SWK and ef.Ruhr for the discussions within the project. The content of section V-B demonstrates the extensibility of the proposed architecture and does not reflect the opinion of the consortium. R EFERENCES [1] E-DeMa Project - Development and Demonstration of Locally Networked Energy Systems to the E-Energy Marketplace of the Future. Project Webpage: http://www.e-dema.de, May 2010. [2] IEEE P2030/D2.1 Draft, Draft Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with the Electric Power System (EPS), and End-Use Applications and Loads. New York, USA: IEEE, May 2010. [3] T. Basso and R. DeBlasio, “Advancing Smart Grid Interoperability and Implementing NISTs Interoperability Roadmap: IEEE P2030TM Initiative and IEEE 1547TM Interconnection Standards,” in Grid-Interop 2009 Conference, November 2009. [4] S. Beer, H. R¨uttinger, L. Bischofs, and H.-J. Appelrath, “Towards a Reference Architecture for Regional Electricity Markets (Entwurf einer Referenzarchitektur f¨ur regionale Elektrizit¨atsm¨arkte),” it - Information Technology, vol. 52, no. 2, pp. 58–64, 2010. [5] S. Beer, L. Bischofs, C. Pries, M. Uslar, A. Niee, H.-J. Appelrath, M. Rohr, and M. Stadler, “The eTelligence Reference Architecture A Standard-Based Architecture for Regional Electricity Markets,” in Internationaler ETG-Kongress 2009. VDE Verlag, October 2009, pp. 84–89. [6] IEC 61968, Application integration at electric utilities - System interfaces for distribution management - Part 11: Common information model (CIM) extensions for distribution Ed. 1.0. Geneva, Switzerland: IEC, July 2010. [7] IEC 61970, Energy management system application program interface (EMS-API) - Part 301: Common Information Model (CIM) Ed. 2.0. Geneva, Switzerland: IEC, April 2009. [8] IEC 61850, Communication networks and systems for power utility automation - Part 7-4: Basic communication structure - Compatible logical node classes and data object classes Ed. 2.0, Geneva, Switzerland, March 2010. [9] IEC TC57/TR62357, Power system control and associated communications Reference architecture for object models, services and protocols. Geneva, Switzerland: IEC, July 2003. [10] IEC 62351, Power system control and associated communications Data and communication security - Part 1: Communication network and system security Introduction to security issues. Geneva, Switzerland: IEC, May 2007. [11] NERC CIP 001-009, Cyber Security Standards for Critical Infrastructure Protection. NERC, 2006-2009. [12] NIST Draft 7628, Smart Grid Cyber Security Strategy and Requirements. NIST, September 2009. [13] NIST Draft, Framework and Roadmap for Smart Grid Interoperability Standards Release 1.0. NIST, September 2009. [14] IEEE P1901 Draft, Draft Standard for Broadband over Power Line Networks: MAC and PHY Specifications. New York, USA: IEEE, January 2010.

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