Search results for "Power quality"

Investigation about selective harmonic elimination in unbalanced multilevel inverters

2022

In this paper 5 and 7 levels cascaded H-bridges inverters are considered, feeding by unequal dc voltage sources. The effect of these unbalancing operation is examined concerning harmonic analysis and total harmonic distortion of the output voltages. The system of equations, obtained by the expansion in the Fourier series of phase output voltage, is solved by applying a method of graphic solution that allows obtaining the switching angles able to eliminate the lower order harmonics.

STUDIO, PROGETTAZIONE E REALIZZAZIONE DI SISTEMI DI MISURA, DI CONTROLLO E DI COMUNICAZIONE DEDICATI ALLE SMART GRIDS

L’attività di ricerca descritta nella presente tesi di dottorato si inquadra nell’ambito dello sviluppo di nuove tecnologie e sistemi di misura di tipo distribuito per la gestione delle smart grids, il miglioramento dei livelli di power quality e l’integrazione della generazione distribuita (GD) e dei sistemi di accumulo (SA) da fonti di energia rinnovabili nelle reti di distribuzione. In particolare, la crescente presenza di GD nelle reti a media e bassa tensione (MT/BT) crea possibili criticità per la protezione e l’automazione della rete, la qualità del servizio, la regolazione di tensione, etc. Nello specifico nascono diverse problematiche quali variazioni di tensione e di frequenza, pr…

Uncertainty evaluation in load flow analysis: real MV distribution networks case studies

2018

This work investigates the measurement uncertainty impact on load flow analysis in medium voltage (MV) distribution networks. The considered algorithm is a simplified load flow algorithm (LFA), developed by authors, which is based on the load power measurements at each secondary substation and one voltage measurement at the slack bus (i.e. the voltage at the MV bus bars of the primary substation). In the viewpoint of a real implementation, to reduce monitoring system costs, the LFA makes use of low voltage (LV) load power measurements for all the substations except those of MV users, where MV transducers are usually already installed. The uncertainties on LFA input quantities (load powers a…

Electrical Safety Analysis in the Presence of Resonant Grounding Neutral

2019

The resonant grounding is one of the possible methods of the system neutral grounding for the medium voltage distribution. IEEE standards do define this grounding configuration, but important advantages and drawbacks of the resonant grounding might not be fully known, due to its rather uncommon application in North America. On the other hand, resonant grounding in Europe is imposed by the increased requirements for power quality, especially for medium-voltage (MV) industrial users, imposed to electric utilities by regulatory authorities, with the purpose to protect the interests of users and consumers. Level of the continuity of the service, magnitude and phase of ground-fault currents, mag…

Studio e sviluppo di innovativi sistemi di misura e di comunicazione per le smart grid

PQ and Harmonic Assessment Issues on Low-Cost Smart Metering Platforms: A Case Study

2020

This paper presents a feasibility study on how to implement power quality (PQ) metrics in a low-cost smart metering platform. The study is aimed at verifying the possibility of implementing PQ monitoring in distribution networks without replacing existing smart metering devices or adding new modules for PQ measurements, thus zeroing the installation costs. To this aim, an electronic board, currently used for remote energy metering, was chosen as a case study, specifically the STCOMET platform. Starting from the specifications of this device, the possibility of implementing power quality metrics is investigated in order to verify if compliance with standard requirements for PQ instruments ca…

Compensation of Nonlinearity of Voltage and Current Instrument Transformers

2019

This paper aims at characterizing and improving the metrological performances of current and voltage instrument transformers (CTs and VTs) in harmonic measurements in the power system. A theoretical analysis is carried out to demonstrate that, due to the iron core nonlinearity, CT and VT output signal is distorted even when the input signal is a pure sine wave. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operati…