A Selective Harmonic Compensation and Power Control Approach Exploiting Distributed Electronic Converters in Microgrids

Made available in DSpace on 2020-12-12T01:39:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Norges Forskningsråd This paper proposes an approach to obtain harmonic compensation and power control by exploiting the electronic power converters deployed in low-voltage microgrids. By the proposed approach, distributed harmonic current compensation is achieved without interfering with the converter's power exchange involved in interfacing the local energy resources (e.g., renewable sources, storage devices) with the grid. The control framework refers to a master/slave microgrid architecture where distributed power converters play as slave units, coordinated by a centralized controller; the data exchange among agents occurs periodically, concerns current magnitudes only, and can be fulfilled by communication means of limited performance. The paper shows the achievable results in terms of power quality improvements and discusses the challenges related with the aimed objective. The proposed methodology is evaluated by means of simulation and experimental tests on a single-phase low-voltage microgrid prototype comprising nonlinear loads and two converters. Different cases of generation limits, load variations, voltage levels, voltage distortions, and line parameters are considered in the tests reported. In addition, the robustness of the proposed method to non-ideal and faulty communication links is discussed and shown by means of experimental results. Group of Automation and Integrated Systems Sao Paulo State University (UNESP), Av. Três de Março 511, 18087-180 Sorocaba Department of Electric Power Engineering Norwegian University of Science & Technology (NTNU), O.S. Bragstads plass 2 Graduate Program in Electrical Engineering Federal University of Minas Gerais (UFMG), Av. Antônio Carlos 6627 Department of Management and Engineering University of Padova, Stradella San Nicola 3 Group of Automation and Integrated Systems Sao Paulo State University (UNESP), Av. Três de Março 511, 18087-180 Sorocaba FAPESP: 2016/08645-9 FAPESP: 2017/24652-8 FAPESP: 2018/22172-1 Norges Forskningsråd: f261735/H3

Resilience-oriented control and communication framework for cyber-physical microgrids

Climate change drives the energy supply transition from traditional fossil fuel-based power generation to renewable energy resources. This transition has been widely recognised as one of the most significant developing pathways promoting the decarbonisation process toward a zero-carbon and sustainable society. Rapidly developing renewables gradually dominate energy systems and promote the current energy supply system towards decentralisation and digitisation. The manifestation of decentralisation is at massive dispatchable energy resources, while the digitisation features strong cohesion and coherence between electrical power technologies and information and communication technologies (ICT). Massive dispatchable physical devices and cyber components are interdependent and coupled tightly as a cyber-physical energy supply system, while this cyber-physical energy supply system currently faces an increase of extreme weather (e.g., earthquake, flooding) and cyber-contingencies (e.g., cyberattacks) in the frequency, intensity, and duration. Hence, one major challenge is to find an appropriate cyber-physical solution to accommodate increasing renewables while enhancing power supply resilience. The main focus of this thesis is to blend centralised and decentralised frameworks to propose a collaboratively centralised-and-decentralised resilient control framework for energy systems i.e., networked microgrids (MGs) that can operate optimally in the normal condition while can mitigate simultaneous cyber-physical contingencies in the extreme condition. To achieve this, we investigate the concept of "cyber-physical resilience" including four phases, namely prevention/upgrade, resistance, adaption/mitigation, and recovery. Throughout these stages, we tackle different cyber-physical challenges under the concept of microgrid ranging from a centralised-to-decentralised transitional control framework coping with cyber-physical out of service, a cyber-resilient distributed control methodology for networked MGs, a UAV assisted post-contingency cyber-physical service restoration, to a fast-convergent distributed dynamic state estimation algorithm for a class of interconnected systems.Open Acces

Cooperative Strategies for Management of Power Quality Problems in Voltage-Source Converter-based Microgrids

The development of cooperative control strategies for microgrids has become an area of increasing research interest in recent years, often a result of advances in other areas of control theory such as multi-agent systems and enabled by emerging wireless communications technology, machine learning techniques, and power electronics. While some possible applications of the cooperative control theory to microgrids have been described in the research literature, a comprehensive survey of this approach with respect to its limitations and wide-ranging potential applications has not yet been provided. In this regard, an important area of research into microgrids is developing intelligent cooperative operating strategies within and between microgrids which implement and allocate tasks at the local level, and do not rely on centralized command and control structures. Multi-agent techniques are one focus of this research, but have not been applied to the full range of power quality problems in microgrids. The ability for microgrid control systems to manage harmonics, unbalance, flicker, and black start capability are some examples of applications yet to be fully exploited. During islanded operation, the normal buffer against disturbances and power imbalances provided by the main grid coupling is removed, this together with the reduced inertia of the microgrid (MG), makes power quality (PQ) management a critical control function. This research will investigate new cooperative control techniques for solving power quality problems in voltage source converter (VSC)-based AC microgrids. A set of specific power quality problems have been selected for the application focus, based on a survey of relevant published literature, international standards, and electricity utility regulations. The control problems which will be addressed are voltage regulation, unbalance load sharing, and flicker mitigation. The thesis introduces novel approaches based on multi-agent consensus problems and differential games. It was decided to exclude the management of harmonics, which is a more challenging issue, and is the focus of future research. Rather than using model-based engineering design for optimization of controller parameters, the thesis describes a novel technique for controller synthesis using off-policy reinforcement learning. The thesis also addresses the topic of communication and control system co-design. In this regard, stability of secondary voltage control considering communication time-delays will be addressed, while a performance-oriented approach to rate allocation using a novel solution method is described based on convex optimization

Modeling, Simulation and Decentralized Control of Islanded Microgrids

Modeling, Simulation and Decentralized Control of Islanded Microgrids by Farideh Doost Mohammadi This thesis develops a comprehensive modular state-space model of microgrids containing inverter-based Distributed Energy Resources (DERs). The model is validated and then used for small signal stability enhancement and voltage and frequency control. State space models of various microgrid elements are first derived, which allow for the inclusion of any possible elements such as current controlled inverters that are missing in the literature. Then a complete state space model is obtained to complement the models that are available in the literature and whose objectives are system analysis only as compared to the purpose of this work which is stability enhancement and control design. Specifically,;1. Small signal stability is enhanced by adding current controlled inverters to the microgrid. 2. Decentralized secondary frequency and voltage control techniques are proposed.;For secondary frequency control purposes, at first, the control strategies of different kinds of inverters and storage devices are described. Then, a novel solution is introduced for islanded microgrids by decomposing the system into virtual control areas.;For the secondary voltage control an Average Consensus Algorithm (ACA) is used and applied on a network of agents which has been chosen optimally based on the required connectivity. The main purpose of the ACA is to keep the average voltage of all the buses at a desired level during islanding. Then another control strategy is proposed to improve the voltage profile. While the average voltage is kept fixed by the voltage controlled inverters, this voltage profile smoothness is obtained by dedicating zones to current controlled inverters and defining their responsibilities based on the location of the loads

On the Control of Microgrids Against Cyber-Attacks: A Review of Methods and Applications

Nowadays, the use of renewable generations, energy storage systems (ESSs) and microgrids (MGs) has been developed due to better controllability of distributed energy resources (DERs) as well as their cost-effective and emission-aware operation. The development of MGs as well as the use of hierarchical control has led to data transmission in the communication platform. As a result, the expansion of communication infrastructure has made MGs as cyber-physical systems (CPSs) vulnerable to cyber-attacks (CAs). Accordingly, prevention, detection and isolation of CAs during proper control of MGs is essential. In this paper, a comprehensive review on the control strategies of microgrids against CAs and its defense mechanisms has been done. The general structure of the paper is as follows: firstly, MGs operational conditions, i.e., the secure or insecure mode of the physical and cyber layers are investigated and the appropriate control to return to a safer mode are presented. Then, the common MGs communication system is described which is generally used for multi-agent systems (MASs). Also, classification of CAs in MGs has been reviewed. Afterwards, a comprehensive survey of available researches in the field of prevention, detection and isolation of CA and MG control against CA are summarized. Finally, future trends in this context are clarified