Smart grid applications
The Energy Department of the AIT Austrian Institute of Technology is working towards the future of the energy supply industry by developing automation concepts for intelligent power distribution in smart grids. As these feature heterogeneous, distributed architectures, IEC 61499 compliant open source control system approaches are best suited to the task. Embedded in that standard as Service Interface Function Blocks (SIFBs) for master and slave nodes, POWERLINK is becoming the standard for real-time data communication via Ethernet in smart grid applications.
As fossil energy sources are dwindling and their combustion has been producing issues such as global warming, the future of the world’s energy supply depends on our ability to include renewable sources. Some of these, particularly photovoltaic converters and wind farms, are subject to changing natural forces, thus supplying electricity with less regularity than more traditional forms of generation. Consequently, more and better means of storing energy will be required. Additionally, facilities such as buildings will not only become more energy efficient, some of them will require energy supplies at certain times while supplying electricity at others.
Smart grids are a necessity
This multifaceted power generation and consumption model is contrasting with the straightforward traditional approach featuring one big supplier and a multitude of smallish consumers. It therefore requires distribution networks that are different from the existing lines in that they need to be able to allow energy to flow in more than one direction. This requires smart grids with the ability to react to information acquired from and exchanged with sources of electricity, storage facilities and consumers.
Challenges on a continental scale such as the development of smart grids cannot be addressed locally, so the European Union has launched the European Electricity Grid Initiative (EEGI) within the Strategic Energy Technology (SET) Plan. The initiative’s activities are coordinated by the energy department of the AIT (Austrian Institute of Technology), who are also supplying smart grid expertise to the International Smart Grid Action Network (ISGAN) and the European Energy Research Alliance (EERA).
An open standard is imperative
"One of the challenges we are facing is the heterogeneous hardware structure of power grids," says Dr. Thomas Strasser. Since the end of 2010, Strasser – a scientist with mechanical engineering background – has been managing a project involving the installation of a universal laboratory-scale test and simulation environment for power distribution algorithms as well as smart grid components and systems. Upon completion later in 2012, this laboratory will be used to verify and optimize implementations of power distribution strategies through all stages of development from full simulation to hardware in the loop emulation and ported systems. "As IT-based energy distribution control implementations need to interact with existing local systems and require stability as well as adaptability over lengthy periods, proprietary control mechanisms and communication protocols are out of the question. Open solutions such as POWERLINK will be the choice for our communication backbone."
The implementation strategies for IT-based energy distribution systems used by the scientists in Vienna are based on the international IEC 61499 standard. Aiming at the creation of hardware-independent, portable control applications, it defines a universally valid model for distributed control systems, replacing the cyclic execution model of older standards by an event-triggered version using an object-oriented approach with function blocks. They have been implementing the engineering and runtime environments within 4DIAC (Framework for Distributed Industrial Automation & Control), an open source control system for distributed applications based on the IEC 61499 standard.
For the communication between control system CPUs and remote I/O units in decentralized architectures, a fast and versatile protocol is required. "We were looking at an Industrial version of Ethernet because we expect this wide-spread standard to be around for quite some time," says Filip Andrén MSc, the electrical and automation engineer in charge of implementation. "Major considerations for us were full independence from typological restrictions, the capability of direct cross communication and the availability in open source." Another was the requirement for the real-time protocol to operate on off-the-shelf Ethernet hardware.
Examining the competing protocols used in industrial applications, the scientists found that only one system fulfilled all of these requirements. "Most of the Industrial Ethernet systems are not available as open source at all," says Thomas Strasser. "POWERLINK is the only one for which open source implementations have been published in the form of source code and is also available under a BSD3 (Berkeley Software Distribution) license, which leaves system architects totally unrestricted while protecting their application expertise." Aside of that, in long-running systems, patent considerations can gain importance over time. "This makes it an important asset that the Ethernet POWERLINK Standardization Group (EPSG) is in possession of all relevant patents," adds Filip Andrén. "Usage rights to the patents are therefore transferred as an integral part of the license and users are safe from possible legal threats."
POWERLINK is the smart grid standard
POWERLINK is not only future-proof due to its openness, it is also best suited for communication with remote I/O units in decentralized control system architectures such as 4DIAC. By simply introducing object classes for master and slave nodes and for the conversions between time and event dependent processes, Filip Andrén and Thomas Strasser achieved full integration with the open control system in compliance with IEC 61499. Using Service Interface Function Blocks (SIFBs) for communication over POWERLINK, the scientists created a communication environment that is easily and quickly adaptable to various hardware without requiring modification of the software itself.
In the second half of 2012, these SIFBs will be published as open source implementations and will be incorporated in 4DIAC. Among other things, this will be the foundation for a project called MAS (Multi Agent System) grid, in which distributed local systems will be collaborating without a centralized intelligent control system. POWERLINK will be the only truly IEC 61499 compliant standard for advanced data communication in intelligent electric power distribution networks.