Experimental Investigation and Evaluation of Future Active Distribution Networks

The UK government’s policy to achieve a 20% renewable energy generation target by 2020, will require significant amounts of SSEG (Small-Scale Embedded Generation) to be connected. In addition to the expected economic and environmental benefits, the anticipated growth in SSEG brings with it numerous challenges for the operation of low voltage and medium voltage distribution networks. At present, there are a number of competing active network management concepts being considered to overcome these challenges and at Durham University a concept defined as the Small Scale Energy Zone (SSEZ) has been proposed and is investigated as part of this research. To further this, a bespoke active low voltage distribution network emulator known as the Experimental SSEZ has been developed by the author. Controllable emulated SSEG, controllable energy storage and controllable emulated load are incorporated into this laboratory. A transformation system has been developed to relate the operation of this system to that of low voltage distribution networks. Centralised and distributed network control systems have been developed for the Experimental SSEZ. These systems were used to evaluate, in conjunction with the relevant literature, the implementation of similar systems on future low voltage distribution networks. Both centralised and distributed control system architectures were found to have their merits. This research should therefore be useful in informing design decisions when developing and implementing active distribution network management systems on LV networks

Coordinated management of low voltage power networks with photovoltaic energy sources

Over the last decades, active power networks have reached great attention due to the incorporation of distributed energy resources into low voltage power systems. In this paper, a decentralized energy management strategy is proposed as an efficient way to minimize both active power losses and voltage profile deviation of an distribution power network with photovoltaic solar farms, and also at the same time, aims to improve the reliability and the security of supply. The coordinated energy management concept relies on a two-step optimization approach based on genetic algorithms (GA) and MINLP, in which a multi-objective function is used which takes into account reliability and operational technical constraints in its formulation. The suitability of the proposed methodology is tested on an existing low voltage power system, in which two aspects are considered: firstly, determining the optimal allocation of PV units and secondly, establishing the optimal reschedule of the active power of the generation units partic ipating in the energy mix and minimizing both the real power losses and voltage deviation of the entire power system.This work has been partly funded by the European Union seventh framework program FP7-SMARTCITIES-2013 under grant agreement 608860 IDE4L – Ideal grid for all

Improving actionable observability of large distribution networks for transmission operators to support improved system control, fault detection and mitigation

Copyright © 2017 The Author(s). The widespread introduction of phasor measurement unit (PMUs) in transmission networks is well understood and has improved visibility enhancing grid stability and avoiding low probability events such as blackouts. For many transmission system operators, there is little-to-no visibility of the real-time state of distribution networks beyond the grid supply points. With the increased penetration of distributed energy resources on low- and medium-voltage networks of the state, and thus behaviour, of the distribution network cannot be assumed to follow historical patterns. The future transition to distribution system operator concept requires better visibility, especially around grid supply points, for deploying wide-area control strategies and active network management schemes. This implies active sharing of data between transmission and distribution monitoring systems. There are a number of challenges in extending the use of PMUs to distribution networks. Many of the lessons and best practises at transmission do not translate to the operation of distribution networks, as an exponential increase in network complexity makes it infeasible to perform complex analysis of the complete network model in real time. This paper presents a methodology for addressing the problems faced in deploying microPMUs at the distribution level.Open Grid Systems OGS Studentship

SIMULATION STUDY OF TECHNICAL ANCILLARY SERVICES IN ELECTRICITY DISTRIBUTION SYSTEMS

This thesis was done as part of the research project DeCAS. The EU-funded project aims to analyze technical ancillary services crossing traditional boundaries from high voltage, medium voltage to low voltage, also with regard to their respective market integration concepts. The goal is to achieve an active control concept of the future distribution network where the unnecessary reactive power flows are avoided. The studied network is located in Sundom, Vaasa. Sundom Smart Grid is a living laboratory done in collaboration with ABB, Vaasan Sähkö, Elisa and the University of Vaasa. The main target of this thesis was to examine by PSCAD simulations the addition of distributed generation and to manage the possible network interactions by the means of active network management. An existing simulation model of the SSG was utilized. Some simplifications were made to the model to reduce the simulation time. The simulations consisted of 72 simulation cases, 36 cases with both Fingrid and ENTSO-E reactive power windows. The idea was to start from a basic model without DER-units connected and then make additions of wind turbines, photovoltaics and utilize different control scenarios for them. The results offer information on possible interactions between different voltage levels. DER-units have capabilities for providing the ancillary services. By using ANM to control the flexibilities the amount of distributed generation can be increased significantly in an electricity network. Aggregating will be needed to sum up the smaller production portions and to ease up the marketing process. Also a type of ‘flexible database’ will be needed for the overall coordination of available resources. The database could include real time information about the free production capacities, sizes, distances, scheduling etc.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Enhanced Electric Vehicle Integration in the UK Low Voltage Networks with Distributed Phase Shifting Control

Electric vehicles (EV) have gained global attention due to increasing oil prices and rising concerns about transportation-related urban air pollution and climate change. While mass adoption of EVs has several economic and environmental benefits, large-scale deployment of EVs on the low-voltage (LV) urban distribution networks will also result in technical challenges. This paper proposes a simple and easy to implement single-phase EV charging coordination strategy with three-phase network supply, in which chargers connect EVs to the less loaded phase of their feeder at the beginning of the charging process. Hence, network unbalance is mitigated and, as a result, EV hosting capacity is increased. A new concept, called Maximum EV Hosting Capacity (HC max) of low voltage distribution networks, is introduced to objectively assess and quantify the enhancement that the proposed phase-shifting strategy could bring to distribution networks. The resulting performance improvement has been demonstrated over three real UK residential networks through a comprehensive Monte Carlo simulation study using Matlab and OpenDSS tools. With the same EV penetration level, the under-voltage probability was reduced in the first network from 100% to 54% and in the second network from 100% to 48%. Furthermore, percentage voltage unbalance factors in the networks were successfully restored to their original values before any EV connection.Peer reviewedFinal Accepted Versio

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks

In the last decade, distribution systems are experiencing a drastic transformation with the advent of new technologies. In fact, distribution networks are no longer passive systems, considering the current integration rates of new agents such as distributed generation, electrical vehicles and energy storage, which are greatly influencing the way these systems are operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system through power electronics converters, is unlocking the possibility for new distribution topologies based on AC/DC networks. This paper analyzes the evolution of AC distribution systems, the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409

Smart microgrids and virtual power plants in a hierarchical control structure

In order to achieve a coordinated integration of distributed energy resources in the electrical network, an aggregation of these resources is required. Microgrids and virtual power plants (VPPs) address this issue. Opposed to VPPs, microgrids have the functionality of islanding, for which specific control strategies have been developed. These control strategies are classified under the primary control strategies. Microgrid secondary control deals with other aspects such as resource allocation, economic optimization and voltage profile improvements. When focussing on the control-aspects of DER, VPP coordination is similar with the microgrid secondary control strategy, and thus, operates at a slower time frame as compared to the primary control and can take full advantage of the available communication provided by the overlaying smart grid. Therefore, the feasibility of the microgrid secondary control for application in VPPs is discussed in this paper. A hierarchical control structure is presented in which, firstly, smart microgrids deal with local issues in a primary and secondary control. Secondly, these microgrids are aggregated in a VPP that enables the tertiary control, forming the link with the electricity markets and dealing with issues on a larger scale

Strategic distribution network planning with smart grid technologies

This paper presents a multiyear distribution network planning optimization model for managing the operation and capacity of distribution systems with significant penetration of distributed generation (DG). The model considers investment in both traditional network and smart grid technologies, including dynamic line rating, quadrature-booster, and active network management, while optimizing the settings of network control devices and, if necessary, the curtailment of DG output taking into account its network access arrangement (firm or non-firm). A set of studies on a 33 kV real distribution network in the U.K. has been carried out to test the model. The main objective of the studies is to evaluate and compare the performance of different investment approaches, i.e., incremental and strategic investment. The studies also demonstrate the ability of the model to determine the optimal DG connection points to reduce the overall system cost. The results of the studies are discussed in this paper

Optimization of the operation of smart rural grids through a novel rnergy management system

The paper proposes an innovative Energy Management System (EMS) that optimizes the grid operation based on economic and technical criteria. The EMS inputs the demand and renewable generation forecasts, electricity prices and the status of the distributed storages through the network, and solves with an optimal quarter-hourly dispatch for controllable resources. The performance of the EMS is quantified through diverse proposed metrics. The analyses were based on a real rural grid from the European FP7 project Smart Rural Grid. The performance of the EMS has been evaluated through some scenarios varying the penetration of distributed generation. The obtained results demonstrate that the inclusion of the EMS from both a technical point of view and an economic perspective for the adopted grid is justified. At the technical level, the inclusion of the EMS permits us to significantly increase the power quality in weak and radial networks. At the economic level and from a certain threshold value in renewables’ penetration, the EMS reduces the energy costs for the grid participants, minimizing imports from the external grid and compensating the toll to be paid in the form of the losses incurred by including additional equipment in the network (i.e., distributed storage).Postprint (published version