Matthias Stifter

Applying open standards and open source software for smart grid applications: Simulation of distributed intelligent control of power systems

Open source solutions will enable the acceptance and usage of open standards for smart grid applications. The aim of this work is to demonstrate the possible usage of a distributed automation system for controlling electrical power systems with Distributed Energy Resources (DER). The control approach is based on the IEC 61499 reference model for distributed control system and its open source solution 4DIAC whereas the power system is simulated with the open source software PSAT. In addition, a freely available stack implementation of the IEC 61850 standard for substation automation is used for monitoring the process variables. As an example the coordinated voltage control of an Under-Load Tap Changer (ULTC) is implemented as IEC 61499 control application in the 4DIAC framework and the ULTC model together with a model of the distribution network are simulated in the GNU Octave/PSAT environment.

Towards a Semantic Driven Framework for Smart Grid Applications: Model-Driven Development Using CIM, IEC 61850 and IEC 61499

Power and energy systems are on the verge of a profound change where Smart Grid solutions will enhance their efficiency and flexibility. Advanced ICT and control systems are key elements of the Smart Grid to enable efficient integration of a high amount of renewable energy resources which in turn are seen as key elements of the future energy system. The corresponding distribution grids have to become more flexible and adaptable as the current ones in order to cope with the upcoming high share of energy from distributed renewable sources.The complexity of Smart Grids requires to consider and imply many components when a new application is designed. However, a holistic ICT-based approach for modelling, designing and validating Smart Grid developments is missing today. The goal of this paper therefore is to discuss an advanced design approach and the corresponding information model, covering system, application, control and communication aspects of Smart Grids.

DG DemoNet validation: Voltage control from simulation to field test

Refinements of the voltage control algorithm for the DG DemoNet concept have been developed extensively over the last years. Consequently the next step will be field tests prior to the deployment. This paper describes the (re-)design of the existing prototype algorithm, offline and online simulation environments and testing of the implementation to prepare the central voltage control unit for the field test. The communication links - PLC and radio link - and the MV grids - ‘Großes Walsertal’ and ‘Lungau’ - impose different challenges for the validation of the voltage controller. During the porting of the prototype to the production implementation, the algorithm has run through a major code revision and re-design, to ensure a more general and modular approach for the voltage control algorithm.

Online Reconfigurable Control Software for IEDs

The future energy system has to satisfy a continuously growing demand for electricity and to reduce greenhouse gas emissions. Fulfilling such diverse needs requires the integration of renewable energy resources on a large scale. However, the existing information and communication infrastructure controlling the corresponding power grids and components is not directly designed to master the ever increasing complexity. An upcoming requirement is the need for the functional adaption of the control systems during operation. The main aim of this article is to discuss and analyze requirements as well as to introduce a standard-compliant concept for a reconfigurable software architecture used in intelligent electronic devices for distributed and renewable energy resources. A simulation case study shows the applicability of this approach. A secure adaptation of the functional structure and the corresponding algorithms in device controllers can substantially contribute to a more efficient energy system, while at the same time responding to future needs.

Co-simulation of components, controls and power systems based on open source software

There exists no universal tool to analyze the increasing complexity in smart grids. Domain specific simulation and engineering tools partly address the challenges of complex system behavior. Different component technologies, customer behavior and controls in the power networks are interacting in a highly dynamic manner. Results of isolated simulations may be not accurate enough on the system level. Free and open available tools like GridLAB-D, PSAT, OpenModelica and 4DIAC are well known and widely used because of their excellent domain specific expertise. With co-simulation approaches the individual strengths of each tool can be exploited to model and simulate the various aspects of complex smart grids. The achieved level of detail and realism potentially surpasses the results that the individual analyses would gain. This paper demonstrates a local smart charging control strategy implemented with the IEC 61499-based standard for distributed control systems. It is simulated with different electric vehicle driving patterns, modeled with the multi-agent environment GridLAB-D. Battery models are defined in OpenModelica and embedded as individual dynamic loads. The power system is simulated using PSAT. This work shows that boundaries and restriction in terms of modeling cross-domain specific problems can be overcome by coupling these open source applications.

Modeling Intelligent Energy Systems: Co-Simulation Platform for Validating Flexible-Demand EV Charging Management

Energy systems experience a rise in complexity: new technologies, topologies and components, tighter links to other systems like markets and the increased usage of information technology. This leads to challenging questions that can not be answered via traditional methods. The goal of including renewable energy and clean technologies in the grid, however, requires solutions for the resulting complex problems. This paper investigates dynamic demand response for intelligent electric vehicle charging as a use-case for detailed hybrid models that cannot be properly handled by traditional tools alone. Universal modeling languages and specialized domain-specific modeling solutions are brought together via standardized co-simulation interfaces to achieve maximal flexibility and minimal implementation efforts. This combination of previously numerically incompatible modeling paradigms enables a detailed look into the dynamics of hybrid component models while keeping the comfort and the strength of established tools. This coupling of a Modelica-based physical simulation engine, a commercial power system simulation tool and an agent-based discrete event simulator for energy grids results in a novel co-simulation platform. This visionary concept provides the high level of detail, scope, flexibility, scalability and accuracy in simulations needed to analyze and optimize energy systems of the future.

Co-Simulation Training Platform for Smart Grids

Power systems training and education faces serious challenges due to the rising complexity of energy systems. This paper presents a simulation-based training platform for educating students and power systems professionals in complex Smart Grid applications. The system is split into parts like electrical grid or controls and specialized, domain-specific tools are then coupled to be able to simulate the overall behavior. Experiences with the developed education and training material and the corresponding modeling and simulation environment are discussed. The usage of advanced modeling and simulation approaches, especially when providing new functionality via coupling of simulation, is an accessible way to train and educate students efficiently in the complex and interdisciplinary area of power systems.

Interfacing Power System and ICT Simulators: Challenges, State-of-the-Art, and Case Studies

With the transition toward a smart grid, the power system has become strongly intertwined with the information and communication technology (ICT) infrastructure. The interdependency of both domains requires a combined analysis of physical and ICT processes, but simulating these together is a major challenge due to the fundamentally different modeling and simulation concepts. After outlining these challenges, such as time synchronization and event handling, this paper presents an overview of state-of-the-art solutions to interface power system and ICT simulators. Due to their prominence in recent research, a special focus is set on co-simulation approaches and their challenges and potentials. Further, two case studies analyzing the impact of ICT on applications in power system operation illustrate the necessity of a holistic approach and show the capabilities of state-of-the-art co-simulation platforms.

Steady-state co-simulation with PowerFactory

Power system analysis applications like PowerFactory make it possible to investigate research questions within a dedicated domain specific environment. With the increasing complexity in cyber-physical systems the need for coupling models or systems for simulation becomes eminent. By utilizing and extending existing interfacing mechanisms the pros and cons for different coupling approaches under different simulation time scales (steady state, transient) are compared. The tight coupling using steady-state simulation together with external simulators have a significant increase in performance and usability. This paper shows the different possibilities of coupling a power system simulation application, namely PowerFactory, with other continuous and discrete event models and simulators. Selected examples for co-simulation applications are discussed.

Loose coupling architecture for co-simulation of heterogeneous components

Co-simulation of different domains is the method of choice if specialised tools exist for each domain and no monolithic solution is available. Motivated by the need for simulation and emulation of networked smart grid systems with interlinked controller, communication and power hardware components, this paper proposes a solution for loose coupling of heterogeneous components (i.e. continuous and time-triggered subsystems). The focus is on a lightweight message bus, allowing multiple simulators to exchange the same messages like in the real system. The architecture allows fast configuration and easy switching between emulated and real-world components. The solution is applied and verified in the context of a Smart Grid application. Photovoltaic inverters in a distribution grid are coordinated with a central onload tap change transformer in order to keep the grid voltages within the limits set by operation rules.