Improving Angle Stability by Switching Shunt Reactors in Mixed Overhead Cable Lines. An Italian 400 kV Case Study

Stringent environmental constraints make the construction of new transmission overhead lines more and more difficult. Alternatively, today it is possible to use cable lines for high (HV) and extra-high (EHV) voltage systems. The configuration of the so-called mixed lines can create some problems in the operation of the electrical system, both during steady-state and transient conditions. In particular, the system stability is one of the main concerns when analyzing the dynamic response of power systems. In this paper, the study of angular stability of a system containing a mixed line is presented: a specific control logic applied to the shunt reactors of the mixed line is proposed as improvement of the overall system stability. The proposed switching logic is first discussed from a theoretical point of view and validated with two different testing systems. Then, the existing overhead-cable lines connecting Sicily to the rest of continental Europe 400 kV power system are taken as case study for the application of the proposed switching strategy. Several simulations are performed in the power system analysis software NEPLAN360: the results show the fundamental role of the timing of the control actions applied on the shunt reactors in helping the system to keep the stability. The proposed control proves to be an effective support to the system subjected to critical contingencies, contributing decisively to avoid the angular separation between areas and therefore to preserve the stability of the system

Synchronizing Interactions Between Different Types of Grid-Forming Converters in Smart Grids

The work investigates the transient synchronizing interactions between different types of grid-forming controls. Two well-known grid-forming schemes are implemented and considered for analysis: a droop-based control and a swing-based control. The two controls are examined for a temporary loss of synchronism. The analysis is performed considering two different conditions for the grid interconnecting the converters: a resistive-inductive grid and a mainly inductive grid. The first case corresponds to actual conditions in low and medium voltage applications. The second case is realized with the implementation of a virtual reactance in the grid-forming control scheme. The analysis of the results provides a specific insight on the characteristics of the synchronizing interactions between the different types of grid-forming converters, indicating the possibility of steep reactions, mutual oscillations and unsymmetrical interactions

Building Automation and Control Systems and Electrical Distribution Grids: A Study on the Effects of Loads Control Logics on Power Losses and Peaks

Growing home comfort is causing increasing energy consumption in residential buildings and a consequent stress in urban medium and low voltage distribution networks. Therefore, distribution system operators are obliged to manage problems related to the reliability of the electricity system and, above all, they must consider investments for enhancing the electrical infrastructure. The purpose of this paper is to assess how the reduction of building electricity consumption and the modification of the building load profile, due to load automation, combined with suitable load control programs, can improve network reliability and distribution efficiency. This paper proposes an extensive study on this issue, considering various operating scenarios with four load control programs with different purposes, the presence/absence of local generation connected to the buildings and different external thermal conditions. The study also highlights how different climatic conditions can influence the effects of the load control logics

New Energy Corridors in the Euro-Mediterranean Area: The Pivotal Role of Sicily

The present paper deals with the new opportunities deriving from the interconnections of the European and North African transmission systems. In order to achieve a single international market for electricity exchanges, interconnections between networks in different countries are becoming increasingly important and Sicily, for its geographical position in the middle of the Mediterranean Sea, will undoubtedly play an important role as an electrical bridge between Europe and the North Africa in the near future. The paper, presenting the actual electro-energetic context of Tunisia, reports the new important interconnection already realized in South Italy (in particular in Sicily) and describe the planned interventions of the near future. In the second part of the paper, using the Neplan software package (10.7.4, NEPLAN AG, CH-8700 Küsnacht (ZH), Switzerland) for simulating the grid, some load flows are carried out to check some operating scenarios (2020 and 2025) considering energy flows from north to south, avoiding system violations

Assessing the Grid Impact of Renewable Energy Communities in a Small Island

The paper presents a study carried out on the island of Pantelleria aimed at assessing the impact of the rise of renewable energy communities (RECs) on the distribution grid parameters. A comparison of various scenarios is done considering different operational strategies of BESSes and electric storage water heaters and different penetration of photovoltaic systems, whose maximum power is defined according to the Italian requirements for small islands (Decree “Isole minori”). The analysis of the impact on the grid is a key element for the evolution and development of RECs in small islands. The study highlight the beneficial impacts of RECs on the distribution grid if associated with suitable Demand Response strategies

A Methodology for Exploiting Smart Prosumers’ Flexibility in a Bottom-Up Aggregation Process

The electrical power system is evolving in a way that requires new measures for ensuring its secure and reliable operation. Demand-side aggregation represents one of the more interesting ways to provide ancillary services by the coordinated management of a multitude of different distributed resources. In this framework, aggregators play the main role in ensuring the effectiveness of the coordinated action of the distributed resources, usually becoming mediators in the relation between distribution system operators and smart prosumers. The research project DEMAND recently introduced a new concept in demand-side aggregation by proposing a scheme without a central aggregator where prosumers can share and combine their flexibility with a collaboration–competition mechanism in a platform called Virtual Aggregation Environment (VAE). This paper, after a brief introduction to the DEMAND project, presents the algorithm for the day-ahead estimation of prosumers’ flexibility and the cooperative–competitive algorithm for the bottom-up aggregation. The first algorithm evaluates various couples of power variation and desired remuneration to be sent to the VAE for further elaborations and, for showing its potentiality, is applied to two different case studies: a passive user with only controllable loads and prosumers with controllable loads, photovoltaics and a storage system. The aggregation algorithm is instead discussed in detail, and its performance is evaluated for different population sizes

FROM FUEL BASED GENERATION TO SMART RENEWABLE GENERATION: PRELIMINARY DESIGN FOR AN ISLANDED SYSTEM. PART I: TECHNICAL ISSUES AND FUTURE SCENARIOS

The subject addressed in this paper is the analytical study of the transition of the energy generation system for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. The paper outlines the technical issues related to such transition from one type of system to the other. The study is carried out for a real islanded MV/LV distribution network located in the Island of Pantelleria. The economical issues regarding the above transition are focused in a companion paper