Search results for "Power System"

Extension and Tuning of Virtual Synchronous Machine to Avoid Oscillatory Instability in Isolated Power Networks

2020

The risk of oscillatory instability introduced by virtual synchronous machines (VSM) control in isolated power networks is investigated. The considered control is a common scheme widely studied in literature, in several configurations and for different case studies. The impact of the VSM control on the system stability is examined for the existing power network of a Mediterranean island. The VSM control is implemented within the power converters interfacing the energy storage systems (ESS) installed in the network. Simulations and analysis show the occurrence of oscillatory instability in the system, with the ESS-VSM and the synchronous machines of the network progressively swinging against…

Energy self-consumers and renewable energy communities in Italy: New actors of the electric power systems

2021

Abstract The new European Directive RED-II on the promotion of the use of renewable energy sources has introduced the concept of the Renewable Energy Community. This new entity has the potential to change the relations among end-users and the latter and the other actors of the energy sector. In particular, the electrical sector appears the most influenced by the implementation of this paradigm. Indeed, the need for self-consumption and for exploiting the full potential of renewable energy in a Renewable Energy Community influences how the end-users exchange energy with the power grid, the rules for their connection to the grid, the implementation of Demand Response and other energy manageme…

Optimal reconfiguration of weakly meshed distribution systems

2011

In this paper the problem of optimal reconfiguration for weakly meshed systems is dealt with; meshes are created by the presence of Favoured Customers (FC) requiring supply through two different paths in order to guarantee the maximum service continuity. Aim of the reconfiguration is to attain a network that operates with minimum power losses, and in order to account for particular needs of the FC loads, that shows the minimum overall yearly fault rate on the branches where the power required by the loads flows. Moreover the constraints concerning the bus voltage profiles, the current in branches and the power balance among HV/MV transformers supplying the network must be full-filled. Due t…

A New Protection Strategy for Electrical Distribution Systems

2010

In this paper, the authors propose a new protection strategy for electrical Medium Voltage distribution networks, based on a distributed intelligence system composed of a central unit and of many local processing units. The distributed intelligence system can precisely identify and locate faults in suitably limited times. Each local processing unit is composed of a data acquisition system and a data analysis system. The first allows the accurate reconstruction of the fundamental using only 1.5 cycles of under fault transient electrical quantities. The second performs suitably precise on-line fault diagnosis based on the data provided by the data acquisition module. The data acquisition algo…

A Comparison between RMS and EMT Grid-Forming Implementations in MATLAB/Simscape for Smart Grids Dynamics

2022

The article presents a comparison between phasor RMS and EMT models for grid-forming converters. The specific aspects related to the implementation in Simscape Electrical of MATLAB/Simulink are discussed for both RMS and EMT time-domains. The comparison between the different implementations is performed with the simulation of two widely studied grid-forming schemes, the virtual synchronous machine and the power-synchronization control. The simulation-based comparison examines transient phenomena with different characteristics and time scales, including frequency transients, phase jumps and short-circuit events. Specific indications regarding limitations and suitability of grid-forming model…

A Study of Power-Frequency Dynamics in Isolated Power Networks with 100% Converter-Interfaced Generation

2020

The operation of a system with 100% converter-interfaced generation poses several questions and challenges regarding various aspects of the dynamic characteristics of the system. The effects related to the power-frequency control are among the most relevant issues which need to be investigated. The paper takes into examination the case of an existing isolated power network of a geographical island assuming a completely converter-interfaced generation. The factors playing a fundamental role in the assessment of which sources should be designated to be grid-forming are identified with a small signal model formulation of a generic multiple oscillators system. Simulations and analysis performed…

WIRELESS DETECTION OF PD PATTERNS: APPLICATIONS IN SMART GRIDS AND MODERN POWER SYSTEMS

In this thesis, different challenges for various applications of a wireless PD detection instrument are discussed and relevant solutions are proposed. The main purpose is to assess the applicability of such technology both in current HV and MV power systems as well as in future applications for smart grids. The main challenges for these types of diagnostic systems are the following: • voltage synchronization of Phase Resolved PD pattern; • PD recognition under non-sinusoidal voltage waveforms; • PD recognition under sinusoidal voltage superimposed harmonics; • PD recognition in laboratory and in real world situations under noise and other source of disturbance. Thanks to the collaboration w…

Challenges in Energy Systems for the Smart- Cities of the Future

2012

In the last years the European Union has actively promoted the renewable energies and the Combined Heat and Power (CHP) also for residential and tertiary buildings. The exploitation of renewable sources and cogeneration seems hampered by the regulatory wall that prohibit for residential, tertiary and commercial buildings the constitution of users clusters. In fact, the unification up to a threshold value of some tens of kVA, at least, can facilitate the installation of renewable energy power plants as solar PV modules or CHP systems (cogeneration) or CCHP systems (tri-generation), overcoming technical and economical barriers and combining several load profiles. The actual distribution syste…

Grid-Forming Converters in Weak Grids – The Case of a Mediterranean Island

2019

The existing power network of a Mediterranean island is used as test bed for the study of grid-forming converter dynamics in weak grid conditions. The control scheme adopted for the converter falls in the category of the so called virtual synchronous machines (VSM). Particular attention is committed to the interaction between the converter controls and the synchronous machines dynamics. Time delays typically associated to measurements and filters are considered in the study, and included in the system model with a specific mathematical approach. Time-domain simulations show the occurrence of oscillatory instability in the system, with VSM and synchronous machines swinging against each other…

Enabling peer-to-peer User-Preference-Aware Energy Sharing Through Reinforcement Learning

2020

Renewable, heterogeneous and distributed energy resources are the future of power systems, as envisioned by the recent paradigm of Virtual Power Plants (VPPs). Residential electricity generation, e.g., through photovoltaic panels, plays a fundamental role in this paradigm, where users are able to participate in an energy sharing system and exchange energy resources among each other. In this work, we study energy sharing systems and, differently from previous approaches, we consider realistic user behaviors by taking into account the user preferences and level of engagement in the energy trades. We formulate the problem of matching energy resources while contemplating the user behavior as a …