Marija Stevic

Cosimulation for Smart Grid Communications

Migration from todays power systems to future smart grids is a necessity as the energy demand continues to grow and an increasing amounts of renewable energies need to be accommodated in the grid. One of the key enablers of the smart grid is the integration of information and communication technology (ICT) into the grids in order to monitor and control power generation, distribution, and demand. Considering the close interdependence of future smart grids and communication networks, there is a need for numerical simulation to thoroughly understand the impact of the communication networks on the performance of power system dynamics, and vice versa. This paper provides an overview of available simulation techniques for smart grid communications with a focus on cosimulation frameworks and their enabling technologies. A decision tree comparing relative advantages of available cosimulation platforms and providing guidelines on how to select from them for a given application is presented. A case study analyzing agent-based shipboard smart grid protections with VPNET is presented.

Development of a simulator-to-simulator interface for geographically distributed simulation of power systems in real time

The geographically distributed simulation concept enables connecting laboratories over long distances with the goal of sharing simulation resources and integrating multiple (Power) Hardware-in-the-Loop setups. The main obstacle in applying this concept is the impact of the communication medium on fidelity and stability of the simulation. This paper presents advantages and challenges of developing a simulator-to-simulator interface based on the time-frequency representation of interface quantities. The proposed approach is first analyzed using a simple electrical circuit as case study, and then conclusions are verified on a larger system including voltage-source converters that realize a high-voltage dc point-to-point link which connects two ac systems. To assess the approach in a realistic framework, an Internet-distributed simulation platform that integrates two remote real-time digital simulators, OPAL-RT (located at University of South Carolina, USA) and OPAL-RT (located at RWTH Aachen University, Germany) is developed and both linear and nonlinear system models are simulated.

A two-step simulation approach for joint analysis of power systems and communication infrastructures

Given the role of information and communication technologies in future smart grids, design of interdependent power and communication networks should be performed concurrently. For this purpose, it is critical to have adequate simulation tools, able to support the process from the preliminary stage to the final implementation. A comprehensive commercial package for joint design is still not available, although prototyping solutions have been developed and proposed in literature. In this paper, we review a simulation approach based on two steps, supported by an off-line co-simulation tool and a real-time power system simulator combined with communication emulation. The two steps are not independent, as co-simulation results are the basis for real-time testing. The application of the proposed simulation approach is demonstrated through a simple although concrete example.

A multi-site real-time co-simulation platform for the testing of control strategies of distributed storage and V2G in distribution networks

This paper presents a real-time co-simulation platform aimed to test control strategies for the management of the interaction between a smart grid and active prosumers. The main feature of the proposed framework relies on the multi-site approach that allows the decoupling between the network model and the system under test. This allows separate testing with the exchange of a limited amount of information between the two systems, helping to preserve the confidentiality of data belonging to different parties. As an example the paper addresses the development and testing of a distributed storage and vehicle-to-grid management system connected to a real distribution network model.

Feasibility of geographically distributed real-time simulation of HVDC system interconnected with AC networks

Numerical simulation is an essential tool to study and design HVDC grids interconnected with AC networks. Detailed real-time simulation of such complex power systems requires large computational resources. The connection of remote laboratories provides the possibility to share available resources thus meeting these demanding computational requirements. This concept is referred to as geographically distributed simulation. This paper presents a feasibility study of geographically distributed real-time simulation realized through the connection of two OPAL-RT real-time digital simulators, located at SINTEF (Trondheim, Norway) and ACS (RWTH Aachen University, Germany). A simple HVDC point to point link that connects two AC systems is adopted here as a study.

Virtual integration of laboratories over long distance for real-time co-simulation of power systems

The interest in the virtual integration of hardware and software assets located at geographically dispersed locations, although not new, has spiked recently. However, realizing joint real-time simulation in connected laboratories is posing new challenges. This paper discusses the generalized requirements of a framework for the virtual integration of laboratories and presents the architecture of the platform that integrates two real-time digital simulators (RTDS located at ACS, RWTH Aachen University, Germany, and OPAL-RT at Politecnico di Torino, Italy). The platform enables remote and online monitoring of the entire interconnected system which is a step towards developing Simulation as a Service concept. The application of this platform for real-time co-simulation of interconnected transmission and distribution systems is demonstrated.

A European Platform for Distributed Real Time Modelling & Simulation of Emerging Electricity Systems

This report presents the proposal for the constitution of a European platform consisting of the federation of real-time modelling and simulation facilities applied to the analysis of emerging electricity systems. Such a platform can be understood as a pan-European distributed laboratory aiming at making use of the best available relevant resources and knowledge for the sake of supporting industry and policy makers and conducting advanced scientific research. The report describes the need for such a platform, with reference to the current status of power systems; the state of the art of the relevant technologies; and the character and format that the platform might take. This integrated distributed laboratory will facilitate the modelling, testing and assessment of power systems beyond the capacities of each single entity, enabling remote access to software and equipment anywhere in the EU, by establishing a real-time interconnection to the available facilities and capabilities within the Member States. Such an infrastructure will support the remote testing of devices, enhance simulation capabilities for large multi-scale and multi-layer systems, while also achieving soft-sharing of expertise in a large knowledge-based virtual environment. Furthermore the platform should offer the possibility of keeping confidential all susceptible data/models/algorithms, enabling the participants to determine which specific data will be shared with other actors. This kind of simulation platform will benefit all actors that need to take decisions in the power system area. This includes national and local authorities, regulators, network operators and utilities, manufacturers, consumers/prosumers. The federation of labs is created through real-time remote access to high-performance computing, data infrastructure and hardware and software components (electrical, electronic, ICT) assured by the interconnection of different labs with a server-cloud architecture where the local computers or machines interact with other labs through dedicated VPN (Virtual Private Network) over the GEANT network (the pan-European research and education network that interconnects Europes National Research and Education Networks ). The local VPN servers bridge the local simulation platform at each site and the cloud ensuring the security of the data exchange while offering a better coordination of the communication and the multi-point connection. It is then possible the integration of the different sub-systems (distribution grid, transmission grid, generation, market, and consumer behaviour) with a holistic approach

Empirical study of simulation fidelity in geographically distributed real-time simulations

Interconnection of digital real-time simulators over wide-area communication networks is an innovative approach to extend local real-time simulation capabilities to enable large-scale simulations. Furthermore, it allows the integration of geographically distributed assets as Power Hardware-in-the-Loop and Controller Hardware-in-the-Loop, thus providing a flexible framework for performing unique research experiments. In most cases, it is not possible to perform large scale real-time simulations and comprehensive experiments locally due to lack of simulation capacity and unavailability of unique assets. Main challenge associated with geographically distributed real-time simulation is to ensure simulation fidelity of the same degree as in the case when the entire simulation is performed at the same location. Simulation fidelity in geographically distributed real-time simulation is investigated and an empirical characterization is provided in this paper. Fidelity degradation caused by different values of time delay and sending rate of data exchange between two digital real-time simulators is presented. Two methods for representation of interface quantities in co-simulation interface algorithms are considered for performing simulations. The first method is based on representation of interface quantities as root mean square of magnitude, frequency, and phase angle of the current and voltage waveforms. The second method utilizes representation of interface quantities in form of time-varying Fourier coefficients, known as dynamic phasors. The empirical study is performed for transmission-distribution co-simulation using two racks of Real-Time Digital Simulator (RTDS®).