Integrating Low Voltage Distribution Systems to Distribution Automation

The aim of this thesis is to define and study the key elements and the main characteris-tics of the integration of the low voltage (LV) distribution systems to distribution auto-mation (DA). The key elements are defined by studying the development of essential systems in LV distribution networks as well as by studying the development of the net-works by way of evolution phases. The key elements and the main characteristics of the integration to DA are illustrated by a certain model of a LV distribution network under its development. For a start DA is reviewed by generally used functions and by technologies. The review includes the data and the information systems and in addition the communication net-works are studied generally. Thereafter the main elements of LV distribution networks are presented and their evolution visions are introduced. The main elements comprises of the distribution network, distributed generation, smart energy metering, electric vehicles and energy storages. The approach to the integration is the evolution of LV distribution networks, so four main evolution phases are introduced; traditional, boom of distributed generation, mi-crogrid and intelligent microgrid. The evolution phases bases on general research publi-cations and visions of Smart Grids. Management architectures for the networks are pre-sented. Also requirements for communication are evaluated by studying the number of nodes, capacity requirements for transferred data types and fault and event frequencies. In order to define a proposal for integrating LV distribution networks to DA, the man-agement architectures and the studied requirements are compared to produce functions for DA. As a result, the proposal is presented based on the studied architectures and re-quirements. In addition considerable issues are introduced relating to the functions in devices or sub-systems, which are needed for DA applications. This thesis indicates the need for further studies, such as: Which are the desired DA functions to be extended to LV distribution networks? Which device or system should offer the desired functions? How well the potential protocols using some media type serves the functions?fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Active network management scheme for reactive power control

In the future new options to provide needed technical ancillary services locally and system-wide by distributed energy resources (DER) are needed. One ancillary service which DER could provide is the reactive power management when microgrid is operated in utility grid-connected mode. In this paper different requirements for reactive power flow between distribution and transmission grids were considered in Sundom Smart Grid (SSG) and the measured data from SSG was used for developing a concept for reactive power management. Based on these different requirements “Future Reactive Power Window” was formulated for SSG which was the basis for control scheme formulation. The simulations showed that coordinated reactive power management scheme across different voltage levels by utilizing control of distributed generation could be very beneficial to the voltage support ancillary service.fi=vertaisarvioitu|en=peerReviewed

Advanced islanding detection in grid interactive microgrids

In the future active network management and protectionsolutions have to enable utilization of intended islandoperation as well as active control and utilizationflexibilities during normal and islanded operation ofgrid interactive microgrids. In this paper, combinedislanding detection schemes for both MV and LVnetwork connected distributed generation units duringnormal grid-connected operation are studied.Utilization of active network management functionalityat MV level enables to control the reactive powerunbalance continuously in order to ensure reliableislanding detection without non-detection zone.Combined scheme also prevents maloperations due toother disturbances.fi=vertaisarvioitu|en=peerReviewed

Modelling battery energy storage systems for active network management : coordinated control design and validation

Control of battery energy storage systems (BESS) for active network management (ANM) should be done in coordinated way considering management of different BESS components like battery cells and inverter interface concurrently. In this paper, a detailed and accurate lithium‐ion battery model has been used to design BESS controls, thereby allowing improved overall power system control design optimisation studies by simultaneously considering both component and system‐level aspects. This model is utilised to develop a multi‐objective ANM scheme (a) to enhance utilisation of wind power generation locally by means of active power (P)‐ control of BESSs; (b) to utilise distributed energy resources (i.e. BESS and wind turbine generators) to maintain system voltage within the limits of grid code requirements by reactive power/voltage (QU)‐ and active power/voltage (PU)‐ controls. BESS control strategies to implement the ANM scheme, are designed and validated through real‐time simulation in an existing smart grid pilot, Sundom Smart Grid (SSG), in Vaasa, Finland.© 2021 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.fi=vertaisarvioitu|en=peerReviewed

Multi-objective active network management scheme studied in Sundom smart grid with MV and LV network connected DER units

Use of controllable, flexible, distributed energy resources (DER) in MV and LV networks will be in key role in order to improve local and system-wide grid resiliency and maximize utilization of renewable energy sources (RES). These resources will provide different technical services as part of future active network management (ANM) schemes. Therefore, future ANM and protection methods and solutions have to be adapted and developed so that active control and utilization of DER during both grid-connected and islanded operation modes is enabled. In this paper, multi-objective ANM scheme is studied by PSCAD simulations during grid-connected operation of Sundom Smart Grid. Based on the simulation results conclusions are stated, for example, related to preventing unwanted MV and LV network reactive power / voltage control interactions and potential mutual effects between voltage (U) and frequency (f) control functions (QU-, PU- and Pf -control) of DER units which are actively participating on studied multi-objective ANM scheme.fi=vertaisarvioitu|en=peerReviewed

Evolution of the Electricity Distribution Networks : Active Management Architecture Schemes and Microgrid Control Functionalities

The power system transition to smart grids brings challenges to electricity distribution network development since it involves several stakeholders and actors whose needs must be met to be successful for the electricity network upgrade. The technological challenges arise mainly from the various distributed energy resources (DERs) integration and use and network optimization and security. End-customers play a central role in future network operations. Understanding the network’s evolution through possible network operational scenarios could create a dedicated and reliable roadmap for the various stakeholders’ use. This paper presents a method to develop the evolving operational scenarios and related management schemes, including microgrid control functionalities, and analyzes the evolution of electricity distribution networks considering medium and low voltage grids. The analysis consists of the dynamic descriptions of network operations and the static illustrations of the relationships among classified actors. The method and analysis use an object-oriented and standardized software modeling language, the unified modeling language (UML). Operational descriptions for the four evolution phases of electricity distribution networks are defined and analyzed by Enterprise Architect, a UML tool. This analysis is followed by the active management architecture schemes with the microgrid control functionalities. The graphical models and analysis generated can be used for scenario building in roadmap development, real-time simulations, and management system development. The developed method, presented with high-level use cases (HL-UCs), can be further used to develop and analyze several parallel running control algorithms for DERs providing ancillary services (ASs) in the evolving electricity distribution networks.© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Functional Analysis of the Microgrid Concept Applied to Case Studies of the Sundom Smart Grid

The operation of microgrids is a complex task because it involves several stakeholders and controlling a large number of different active and intelligent resources or devices. Management functions, such as frequency control or islanding, are defined in the microgrid concept, but depending on the application, some functions may not be needed. In order to analyze the required functions for network operation and visualize the interactions between the actors operating a particular microgrid, a comprehensive use case analysis is needed. This paper presents the use case modelling method applied for microgrid management from an abstract or concept level to a more practical level. By utilizing case studies, the potential entities can be detected where the development or improvement of practical solutions is necessary. The use case analysis has been conducted from top-down until test use cases by real-time simulation models. Test use cases are applied to a real distribution network model, Sundom Smart Grid, with measurement data and newly developed controllers.. The functional analysis provides valuable results when studying several microgrid functions operating in parallel and affecting each other. For example, as shown in this paper, ancillary services provided by an active customer may mean that both the active power and reactive power from customer premises are controlled at the same time by different stakeholders.© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Compliance of Distribution System Reactive Flows with Transmission System Requirements

Transmission system operators (TSOs) often set requirements to distribution system operators (DSOs) regarding the exchange of reactive power on the interface between the two parts of the system they operate, typically High Voltage and Medium Voltage. The presence of increasing amounts of Distributed Energy Resources (DERs) at the distribution networks complicates the problem, but provides control opportunities in order to keep the exchange within the prescribed limits. Typical DER control methods, such as constant cosϕ or Q/V functions, cannot adequately address these limits, while power electronics interfaced DERs provide to DSOs reactive power control capabilities for complying more effectively with TSO requirements. This paper proposes an optimisation method to provide power set-points to DERs in order to control the hourly reactive power exchanges with the transmission network. The method is tested via simulations using real data from the distribution substation at the Sundom Smart Grid, in Finland, using the operating guidelines imposed by the Finnish TSO. Results show the advantages of the proposed method compared to traditional methods for reactive power compensation from DERs. The application of more advanced Model Predictive Control techniques is further explored.©2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Part of this work was carried out in the SolarX research project with financial support provided by Business Finland, 2019–2021 (grant No. 6844/31/2018).fi=vertaisarvioitu|en=peerReviewed

Socio-technical modelling of customer roles in developing low voltage distribution networks

The transition of low voltage (LV) distribution networks towards more intelligent and smart microgrids is dependent on both technical and behavioral factors, thus forming a socio-technical systems change. Sociotechnical aspects need to be taken into account when developing concepts and models to establish and manage successful niche experiments. This paper presents a new framework to model actor (customer) evolution and engagement in the process of developing smart LV Microgrid distribution networks as socio-technical systems. The framework is based on combining the Multi-level perspective (MLP) and the Strategic niche management (SNM) approach with the Unified Modeling Language (UML) tool. Customer engagement is an essential element in SNM, wherefore understanding their and other actors’ different development paths is invaluable to uncover the dynamics of the Microgrid transition in the societal and the technical contexts. The proposed framework could be applied to other key actors such as DSOs and energy retailers. The benefit of the models created by the developed framework is the articulation of expectations and visions as well as building up the networks in the SNM.fi=vertaisarvioitu|en=peerReviewed

Accelerated Real-Time Simulations for Testing a Reactive Power Flow Controller in Long-Term Case Studies

This paper presents the development of an accelerated real-time cosimulation and testing platform, especially for long-term simulations of power systems. The platform is planned to be utilized in the development and testing of active network management functions for microgrids and smart grids. Long-term simulations are needed in order to study, for example, the potential weekly, monthly, or yearly usage of distribution-network-connected distributed energy resources for different technical flexibility services. In order to test new algorithms in long-term study cases, real-time simulations or hardware-in-the-loop tests should be accelerated. This paper analyzes the possibilities and challenges of accelerated long-term simulations in studying the potential use of a large-scale wind turbine for reactive power flow control between distribution system operator (DSO) and transmission system operator (TSO) networks. To this end, the reactive power flow control is studied for different voltage levels (HV and MV) in the Sundom Smart Grid in Vaasa, Finland. The control of reactive power flow between HV and MV networks is realized with a reactive power window control algorithm for a 3.6 MW MV-network-connected wind turbine with a full-scale power converter. The behaviour of the reactive power controller during long-term simulations is studied by offline and real-time simulations. Moreover, the real-time simulations are performed with both software-in-the-loop and controller-hardware-in-the-loop.Copyright © 2020 Katja H. Sirviö et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.fi=vertaisarvioitu|en=peerReviewed