Device and method for converting direct current into alternate current

The device for converting direct current into alternate current comprises a multilevel converter associated with at least a source of direct current and a modulation unit having piloting means for piloting the converter for the conversion of the direct current into an alternate output current, in which the modulation unit comprises comparison means for comparing the output current value with a preset positive threshold value and a preset negative threshold value, the piloting means being suitable for piloting the converter with a pulse modulation of the unipolar type in the event of the output current value being above the positive threshold value or below the negative threshold value and with a pulse modulation of the complementary type in the event of the output current value being below the positive threshold value and above the negative threshold value. The method for converting direct current into alternate current comprises a piloting phase of a multilevel converter for the conversion of a direct voltage into an alternate output voltage, a comparison phase of the output current value with a preset positive threshold value and a preset negative threshold value, the piloting phase being suitable for piloting the converter with a pulse modulation of the unipolar type in the event of the output current value being above the positive threshold value or below the negative threshold value and with a pulse modulation of the complementary type in the event of the output current value being below the positive threshold value and above the negative threshold value

INVESTIGATING THE SEISMIC RESPONSE OF URM WALLS WITH IRREGULAR OPENING LAYOUT THROUGH DIFFERENT MODELING APPROACHES

The façade and internal walls of unreinforced masonry (URM) buildings often present an irregular opening layout, due to architectural reasons or modifications to the structure, which make the expected seismic damage pattern less predictable a priori. Therefore, the discretization of the walls in structural components is not standardized, conversely to cases with a regular opening layout for which the available modeling methods are corroborated by seismic damage surveys reporting recurrent failure patterns. The structural component discretization is a relevant step for the code-conforming seismic assessment, typically based on comparing the internal forces and drifts of each component to strength criteria and drift thresholds. Therefore, the lack of well-established approaches can significantly influence the assessment. The issue is even more evident when the structural components must be identified a priori in the modeling stage, namely for equivalent frame models. The applicability of available methods for discretization of URM walls with irregular opening layout has been already investigated in literature, but a conclusive judgment requires further studies. In this context, this paper presents an overview of the preliminary results addressing the numerical modeling of this type of walls within the framework of the DPC-ReLUIS 2022-2024 project (Subtask 10.3), funded by the Italian Department of Civil Protection. The Subtask aims to propose consensus-based recommendations for researchers and practitioners which can contribute to harmonize the use of different modeling approaches. Seven research groups are involved in the research, adopting different modeling approaches and computer codes, but similar assumptions and the same analysis method (pushover) are used. The benchmark URM structure illustrated in the paper is a two-story wall from which four configurations with increasing irregularity of opening layout were derived. The results of four modeling approached are presented. Three of them reproduce the mechanical response of masonry at the material scale by means of FE models implemented in OpenSees, DIANA and Abaqus software, while the remaining approach describes the mechanical response of masonry at the macro-element scale in 3DMacro software. Results were compared in terms of capacity curves, predicted failure mechanisms and evolution of internal forces in piers. The adoption of consistent assumptions among the different approaches led to an overall agreement of predictions at both wall and pier scales, particularly in terms of damage pattern with higher concentration of damage at the ground story. Despite that, differences on the pushover curves have been highlighted. They are mainly due to some deviations of the internal forces in squat piers deriving from a complex load flow in these elements

Investigating the seismic response of URM walls with irregular opening layout through different modeling approaches

TThe façade and internal walls of unreinforced masonry (URM) buildings often present an irregular opening layout, due to architectural reasons or modifications to the structure, which make the expected seismic damage pattern less predictable a priori. Therefore, the discretization of the walls in structural components is not standardized, conversely to cases with a regular opening layout for which the available modeling methods are corroborated by seismic damage surveys reporting recurrent failure patterns. The structural component discretization is a relevant step for the code-conforming seismic assessment, typically based on comparing the internal forces and drifts of each component to strength criteria and drift thresholds. Therefore, the lack of well-established approaches can significantly influence the assessment. The issue is even more evident when the structural components must be identified a priori in the modeling stage, namely for equivalent frame models. The applicability of available methods for discretization of URM walls with irregular opening layout has been already investigated in literature, but a conclusive judgment requires further studies. In this context, this paper presents an overview of the preliminary results addressing the numerical modeling of this type of walls within the framework of the DPC-ReLUIS 2022-2024 project (Subtask 10.3), funded by the Italian Department of Civil Protection. The Subtask aims to propose consensus-based recommendations for researchers and practitioners which can contribute to harmonize the use of different modeling approaches. Seven research groups are involved in the research, adopting different modeling approaches and computer codes, but similar assumptions and the same analysis method (pushover) are used. The benchmark URM structure illustrated in the paper is a two-story wall from which four configurations with increasing irregularity of opening layout were derived. The results of four modeling approached are presented. Three of them reproduce the mechanical response of masonry at the material scale by means of FE models implemented in OpenSees, DIANA and Abaqus software, while the remaining approach describes the mechanical response of masonry at the macro-element scale in 3DMacro software. Results were compared in terms of capacity curves, predicted failure mechanisms and evolution of internal forces in piers. The adoption of consistent assumptions among the different approaches led to an overall agreement of predictions at both wall and pier scales, particularly in terms of damage pattern with higher concentration of damage at the ground story. Despite that, differences on the pushover curves have been highlighted. They are mainly due to some deviations of the internal forces in squat piers deriving from a complex load flow in these elements.DPC - Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri(LA/P/0112/2020

Echo cancellation for DVB repeaters

La presente invenzione si riferisce ad un dispositivo ripetitore perfezionato per la cancellazione e/o riduzione di segnali di eco ed al relativo metodo

Equalization of DC Bus Voltage in Three-Level NPC-HB Inverters for PV Applications by Even Harmonics Injection or Fundamental Phase Modulation

The issue of dynamic equalization of the dc bus voltages unbalance is considered in the case of single-phase split-capacitor three-level neutral-point-clamped (NPC) half-bridge inverters for photovoltaic (PV) inverters. The lack of a proper equalization strategy would lead to a rapid drift of dc bus voltages, causing stability problems to the inverter output current control loop and eventually to failure of the power stage. The novel proposal presented in this paper considers the injection of a 2nd harmonic current component (patent pending) or an equivalent modulation of the fundamental current reference phase angle. The presence of a 2nd harmonic component on the grid current is tolerable as far as EMC standards limitations are satisfied, being relatively high when compared to the dc current injection method, which is normally adopted. The proposed equalization strategy has been implemented and tested on a commercial PV inverter. Analytical developments as well as a simulation and experimental investigation are presented to prove the effectiveness of the proposal

System and method for offsetting the input voltage unbalance in multilevel inverters or the like

The system for offsetting the input voltage unbalance in multilevel inverters or the like comprises a control unit operatively associated with a multilevel inverter for converting direct current into alternate current, the control unit being suitable for piloting the multilevel inverter for generating an output current depending on a reference current, and an equalisation unit for equalising the input voltages of the multilevel inverter having first generation means of a harmonic component of order equal to the reference current, out of phase with respect to the fundamental component of the reference current, detection means of the unbalance of the input voltages to the multilevel inverter, regulation means of the amplitude of the harmonic component depending on the detected unbalance, for offsetting the unbalance. The method for offsetting the unbalance of the input voltages in multilevel inverters or the like comprises a control phase of a multilevel inverter for converting direct current into alternate current, in which the multilevel inverter is piloted for generating an output current depending on a reference current, a generation phase of a harmonic component of order equal to the reference current, out of phase with respect to the fundamental component of the reference current, a detection phase of the unbalance of the input voltages to the multilevel inverter and a regulation phase of the amplitude of the harmonic component depending on the detected unbalance, for offsetting the unbalance