Search results for " generation."

Hybrid passive and communications-based methods for islanding detection in medium and low voltage smart grids

2013

Islanding condition takes place when a distributed generator (DG) continues to power a part of the grid even if power from electric utility is no longer present. Adverse effects of islanding are power quality deterioration, grid-protection interference, equipment damage, and personnel safety hazards. For these reasons, DG systems must detect an islanding condition and immediately disconnect from the grid (anti-islanding protection). This paper proposes an hybrid solution, for both low voltage (LV) and medium voltage (MV) applications, which makes use of passive and communication-based methods for islanding detection. Among the existing communication technologies, the study is focused on pow…

Control of solid-state fault current limiter for DG-integrated distribution systems

2017

Fault current limier (FCL) is a device that limits the system current under fault conditions without disconnecting the system and affecting the power system protection components such as circuit breakers. Many types of FCLs have been proposed to limit the magnitude of the fault current. Solid-state fault current limiters (SSFCLs) can limit the peak value of the fault current by applying several methods, such as controlling the system impedance or controlling the voltage that appears across the fault. In this paper, a new control scheme for the SSFCL circuit is presented. The control method is based on controlling the duty cycle of solid state switches to control the rms value of the system …

Flexible power converters for the fault tolerant operation of Micro-Grids

2010

The progressive penetration level of Distributed Generation (DG) is destined to cause deep changes in the existing distribution networks no longer considered as passive terminations of the whole electrical system. A possible solution is the realization of small networks, namely the Micro-Grids, reproducing in themselves the structure of the main production and distribution of the electrical energy system. In order to gain an adequate reliability level of the microgrids the individuation and the management of the faults with the goal of maintaining the micro-grid operation (fault tolerant operation) is quite important. In the present paper flexible power converters and a companion control al…

A New Solution for Low-Voltage Distributed Generation Interface Protection System

2015

In this paper, a new solution is proposed for the remote monitoring and control of distributed generators (DGs) and energy storage systems (ESSs) connected to low-voltage distribution networks. The proposed system fulfills the in-force standard requirements for the connection of DGs to the utility grid. Moreover, it allows implementing some enhanced functions for the remote control of inverters of DGs and ESSs, not only in terms of disconnection but also in terms of voltage regulation and power shuttering. The proposed solution is based on a new interface protection system and a dedicated secondary substation concentrator, which allows the communication between the distributed system operat…

Electric and magnetic emission in near field region and thermal behaviour of power module for photovoltaic application

2015

The new power module, characterized by high power density, miniaturization of packages and layout and high frequency switching, are increasingly used in the field of in automotive, aircraft industry and for Distributed Generation (DG) connected to smart grid. To guarantee the reliability and safety of these systems, the electromagnetic compatibility (EMC) and thermal behavior, have to be carefully considered for these appliances. This paper describes a measurement methodology to characterize the electromagnetic emissions in near field zone produced by a PM prototype and its thermal behavior. In particular, the electric and magnetic fields, in the near field region in the frequency range 9kH…

Exact quantum dynamics of interacting spin systems subjected to controllable time dependent magnetic fields

2020

Small family business performance: comparison between family and non-family enterprises

2010

This study compares small family business performance between the Finnish family and non-family enterprises. The sample (2,004 firms) was derived to represent nationally small businesses, in collaboration with the Statistics Finland (Centre) in Helsinki. The answer rate of the study was 90% (data collected by mail questionnaires and telephone interviews). The method of the study was to compare family and non-family enterprises with ROA (return on assets) on an enterprise population level (Finland). The results of the study show that most of the small family businesses are controlled by the founder generation. Founder generation performance was slightly higher than among descendant generatio…

Life Cycle Assessment of electricity production from refuse derived fuel: A case study in Italy

2020

Biomasses and bio-waste have an important role in decarbonizing the European energy mix, the latter contributing to the transition towards a circular economy. In particular, Refuse Derived Fuel (RFD) - a biofuel obtained from dry residue of waste - appears a really interesting energy option. In this framework this study aims at assessing the environmental profile of electricity generation from RDF in Italy, comparing two different kinds of RDF production and combustion plants. The functional unit is 1 kWh of net electricity from RDF delivered to the grid. Two Italian plants are examined: one located in Ravenna (RDF is produced in a direct flow treatment plant) and the other one in Bergamo (…

Greenhouse Gas Emissions from Wastewater Treatment Plants on a Plantwide Scale: Sensitivity and Uncertainty Analysis

2016

This paper presents the sensitivity and uncertainty analysis of a mathematical model for greenhouse gas emission (GHG) and energy consumption assessment in wastewater treatment plants. A sensitivity analysis was carried out (using two different methods) to determine which model factors have the greatest effect on the predicted values of the GHG production. Further, an uncertainty analysis was carried out to quantify the uncertainty of the key model outputs, such as carbon dioxide production from activated sludge treatment. The results show that influent fractionation factors, which characterize influent composition, have an important role on direct and indirect GHGs production and emission.…

Effect of Integrating Photovoltaic Systems on Electrical Network Losses Considering Load Variation

2018

Planning of Distributed Generation (DG) units in the power distribution networks is an important issue, one of the most important considerations that is directly affected by installing DG units is the power losses. Improper allocation of DG units to the grid can lead to a noticeable increase in the power losses. Moreover, the load variation is considered as critical matter when studying the optimal scenario that minimizes the power losses in the network. The aim of this paper is to investigate the effect of integrating photovoltaic (PV) units on the distribution network losses considering load variation. The optimal parameters of the DG units were calculated for the various load demands in …