An adaptive overcurrent protection scheme for distribution networks

Distribution networks are evolving toward the vision of smart grids, with increasing penetration of distributed generation (DG), introduction of active network management (ANM), and potentially islanded modes of operation. These changes affect fault levels and fault current paths and have been demonstrated to compromise the correct operation of the overcurrent protection system. This paper presents an adaptive overcurrent protection system which automatically amends the protection settings of all overcurrent relays in response to the impact of DG, ANM, and islanding operation. The scheme has been developed using commercially available protection devices, employs IEC61850-based communications, and has been demonstrated and tested using a hardware-in-the-loop laboratory facility. A systematic comparison of the performance of the proposed adaptive scheme alongside that of a conventional overcurrent scheme is presented. This comparison quantifies the decrease in false operations and the reduction of mean operating time that the adaptive system offers

Medium voltage fault location using distributed LV measurements

An MV fault location technique based exclusively on low voltage measurements in the distribution network is presented in this paper. The technique is based on sequence component analysis of the voltage measurements in order to characterise the LV voltage during MV faults. The accuracy of the technique is evaluated using a DigSILENT PowerFactory model where various fault conditions have been studied including the impact of distributed generation connection on the network voltage profile. The model represents the Power Networks Demonstration Centre’s (PNDC) MV and LV test network. This is to facilitate the validation of the model in the future implementing physical fault testing and measurements using the PNDC network

Power hardware in the loop platform for flywheel energy storage system testing for electric ship power system applications

The UK MoD and Power Networks Demonstration Centre (PNDC) have worked collaboratively to de-risk the integration of power system architecture into future and legacy naval platforms This is being achieved through the development of a 540kVA Power Hardware in the Loop (PHIL) testing facility as part of a project arrangement with the US called "The Advanced Electrical Power and Propulsion Systems Development Project." The two key components of the PHIL system are: (1) A real time digital simulator system that is capable of simulating naval electrical systems in real time; and (2) A programmable power converter, a uniquely modular solution that can be re-configured for AC and DC output, which is used as the link between simulation and real hardware under test. The PHIL testbed has been used to investigate a 360kW modular flywheel system developed by GKN. This project involved interfacing the real flywheel to a simulated ship electrical power system. This paper discusses how the PHIL test facility was configured for flywheel testing and the associated challenges, learnings and opportunities from this test setup. This paper also reports on one of the tests that was completed as part of this test program. In this test the FESS is operating in real time connected to a ship power system simulation. The results reported in this paper are particularly significant in that they demonstrate how a real piece of hardware can be tested as part of a ship power system without the need for a full ship demonstrator. This form of testing supports rapid resolution of hardware to ship integration challenges, control methodologies, and power system management schemes for de-risking new systems. This testing is prior to the hardware being connected to any potential full-scale shore based ship demonstrator or being installed directly on-board a ship power system where it could adversely impact ship operation

Characterization of time delay in power hardware in the loop setups

The testing of complex power components by means of power hardware in the loop (PHIL) requires accurate and stable PHIL platforms. The total time delay typically present within these platforms is commonly acknowledged to be an important factor to be considered due to its impact on accuracy and stability. However, a thorough assessment of the total loop delay in PHIL platforms has not been performed in the literature. Therefore, time delay is typically accounted for as a constant parameter. However, with the detailed analysis of the total loop delay performed in this article, variability in time delay has been detected as a result of the interaction between discrete components. Furthermore, a time delay characterization methodology (which includes variability in time delay) has been proposed. This will allow for performing stability analysis with higher precision as well as to perform accurate compensation of these delays. The implications on stability and accuracy that the time delay variability can introduce in PHIL simulations has also been studied. Finally, with an experimental validation procedure, the presence of the variability and the effectiveness of the proposed characterization approach have been demonstrated

Adaptive protection architecture for the smart grid

Unique and varied power system conditions are already being experienced as a result of the deployment of novel control strategies and new generation and distribution related technologies driven by the smart grid. A particular challenge is related to ensuring the correct and reliable operation of protection schemes. Implementing smarter protection in the form of adaptive setting selection is one way of tackling some of the protection performance issues. However, introducing such new approaches especially to safety critical systems such as protection carries an element of risk. Furthermore, integrating new secondary systems into the substation is a complex and costly procedure. To this end, this paper proposes an adaptive protection architecture that facilitates the integration of such schemes into modern digital substations which are a staple of smart grids. Functional features of the architecture also offer powerful means of de-risking schemes and flexible implementation through self-contained modules that are suitable for reuse. An example adaptive distance protection scheme is presented and tested to demonstrate how the architecture can be implemented and to highlight the architecture's novel features

Performance optimisation of a flywheel energy storage system using the PNDC power hardware in the loop platform

The UK MOD has an objective to improve the efficiency and flexibility associated with the integration of naval electrical systems into both new & existing platforms. A more specific challenge for the MOD is in the de-risking of the integration of future pulse & stochastic loads such as Laser Directed Energy Weapons. To address this the Power Networks Demonstration Centre (PNDC) naval research programme is focused towards understanding & resolving the associated future power system requirements. To address these challenges, the UK MOD and the PNDC have worked collaboratively to develop a 540kVA Power Hardware in the Loop (PHIL) testing facility. For the UK MOD this supports the “UK-US Advanced Electric Power and Propulsion Project Arrangement (AEP3).” This testing facility has been used to explore the capabilities of PHIL testing and evaluate a Flywheel Energy Storage System (FESS) in a notional ship power system environment. This testing provided an opportunity to develop and further validate the capability of the PHIL platform for continued marine power system research. This paper presents on the results from PHIL testing of the FESS at PNDC, which involved both characterisation and interfacing the FESS within a simulated ship power system. The characterisation tests involved evaluating the: response to step changes in current reference; frequency and impedance characteristics; and response during uncontrolled discharge. The ship power system testing involved interfacing the FESS to a simulated real time notional ship power system model and evaluating the response of the FESS and the impact on the ship power system under a range of different operational scenarios. This paper also discuss the links between FESS characterisation testing and the development of the energy management system implemented in the real time model. This control system was developed to schedule operation of the FESS state (charging, discharging and idle) with the other simulated generation sources (the active front end and battery storage) and with the loads within the ship power system model. Finally, this paper highlights how the testing at PNDC has also supported the comparison and validation of previous FESS testing at Florida State University’s Centre Advanced Power Systems (FSU CAPS) facility, and how the combined efforts help to collectively de-risk future load Total Ship Integration and Evolving Intelligent Platforms in both UK and US programmes via the AEP3 PA

The role of experimental test beds for the systems testing of future marine electrical power systems

Marine electrical power systems (MEPS) are experiencing a progressive change with increased electrification - incorporation of distributed power generation, high power density requirement, increased storage integration, availability of alternative technologies and incorporation of novel loads to name a few. In recent years, smart grid (advanced land based power systems) concepts have increasingly been incorporated within MEPS to leverage on their proven advantages. Due to the distinct nature of the two power systems, upon incorporation, the solutions need to be further proven by simulations and experimentation. This paper presents two smart grid enabled MEPS test beds at the University of Strathclyde developed to allow for proof of concept validations, prototyping, component characterization, test driven development/enhancement of emerging MEPS solutions, technologies and architectures. The capabilities of the test beds for rapid proof of concept validations and component characterization are discussed by means of two case studies. Drawing on from the two case studies, this paper further presents a discussion on the requirements of systems testing of future more electric MEPS

An integrated pan-European research infrastructure for validating smart grid systems

A driving force for the realization of a sustainable energy supply in Europe is the integration of distributed, renewable energy resources. Due to their dynamic and stochastic generation behaviour, utilities and network operators are confronted with a more complex operation of the underlying distribution grids. Additionally, due to the higher flexibility on the consumer side through partly controllable loads, ongoing changes of regulatory rules, technology developments, and the liberalization of energy markets, the system’s operation needs adaptation. Sophisticated design approaches together with proper operational concepts and intelligent automation provide the basis to turn the existing power system into an intelligent entity, a so-called smart grid. While reaping the benefits that come along with those intelligent behaviours, it is expected that the system-level testing will play a significantly larger role in the development of future solutions and technologies. Proper validation approaches, concepts, and corresponding tools are partly missing until now. This paper addresses these issues by discussing the progress in the integrated Pan-European research infrastructure project ERIGrid where proper validation methods and tools are currently being developed for validating smart grid systems and solutions.This work is supported by the European Community’s Horizon 2020 Program (H2020/2014-2020) under project “ERIGrid” (Grant Agreement No. 654113). Further information is available at the corresponding website www.erigrid.eu

Achievements, experiences, and lessons learned from the European research infrastructure ERIGrid related to the validation of power and energy systems

Power system operation is of vital importance and must be developed far beyond today’s practice to meet future needs. Almost all European countries are facing an abrupt and very important increase of renewables with intrinsically varying yields which are difficult to predict. In addition, an increase of new types of electric loads and a reduction of traditional production from bulk generation can be observed as well. Hence, the level of complexity of system operation steadily increases. Because of these developments, the traditional power system is being transformed into a smart grid. Previous and ongoing research has tended to focus on how specific aspects of smart grids can be developed and validated, but until now there exists no integrated approach for analysing and evaluating complex smart grid configurations. To tackle these research and development needs, a pan-European research infrastructure is realized in the ERIGrid project that supports the technology development as well as the roll-out of smart grid technologies and solutions. This paper provides an overview of the main results of ERIGrid which have been achieved during the last four years. Also, experiences and lessons learned are discussed and an outlook to future research needs is provided.</p