Filip Andren

A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems

Renewable energy sources are one key enabler to decrease greenhouse gas emissions and to cope with the anthropogenic climate change. Their intermittent behavior and limited storage capabilities present a new challenge to power system operators to maintain power quality and reliability. Additional technical complexity arises from the large number of small distributed generation units and their allocation within the power system. Market liberalization and changing regulatory framework lead to additional organizational complexity. As a result, the design and operation of the future electric energy system have to be redefined. Sophisticated information and communication architectures, automation concepts, and control approaches are necessary in order to manage the higher complexity of so-called smart grids. This paper provides an overview of the state of the art and recent developments enabling higher intelligence in future smart grids. The integration of renewable sources and storage systems into the power grids is analyzed. Energy management and demand response methods and important automation paradigms and domain standards are also reviewed.

On the Stability of Local Voltage Control in Distribution Networks With a High Penetration of Inverter-Based Generation

A stability study of distribution networks with a high penetration of distributed generators (DGs) actively supporting the network is presented in this paper. A possible way of mitigating the voltage rise caused by DGs is the local control of reactive power. Among the different possible options, the Q(U) control (reactive power as a function of the voltage) is one of the commonly suggested solutions. However, the Q(U) control can, under certain conditions, lead to instability. This paper summarizes the results of a stability study conducted on a single-inverter system and on a multiinverter system. It shows that the requirements for reaching a stable operation can easily be met for integrated systems but could be a significant constraint for systems relying on communication.

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.

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.

Review of Trends and Challenges in Smart Grids: An Automation Point of View

Low-carbon and energy efficient technologies are seen as key enablers to reduce the green-house gas emissions and to limit the global warming. The large scale penetration of distributed energy resources from renewables seems to be a very promising approach. In order to cope with the fluctuating nature of such energy resources an intelligent integration in todays electric energy infrastructure is necessary. Such intelligent power networks--called Smart Grids--tend to have a higher complexity compared to the traditional infrastructure. They need advanced control approaches in order to be manageable. The development of more sophisticated information, communication and automation technologies and control algorithms are in the focus of the research community today in order to master the higher complexity of Smart Grid systems. This paper provides a review of automation trends and challenges for the future electric energy infrastructure with focus on advanced concepts using artificial intelligence and multi-agent systems. Moreover, most important standards and common rules are also discussed in order to satisfy interoperability issues in such a distributed environment.

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.