1,326 research outputs found
Unintentional Islanding in Distribution Networks with Large Penetration of Power Electronics and Renewable Energy Systems
No full textThe PhD thesis focus on the analysis and investigation of a crucial issue related to increasing number of distributed energy resources (DERs). This recent issue is the unintentional (i.e. uncontrolled) islanding operation in distribution network with large penetration of DERs based on power electronic converters. Particular focus has been addressed to the interaction between DERs, protection systems and new connection rules required by standard bodies. The aim of the research activity is the investigation on the causes and the influencing factors of unintentional islanding in medium and low voltage (MV and LV) distribution network.
The unintentional islanding issue has interested many studies and publications over the last decades. However, the literature research is lacking of considering the lately introduced European standards and technical specifications for DERs. Therefore, during the PhD research, novel aspects of how requirements and ancillary services influence the unintentional islanding operations have been studied, highlighting novel relevant factors, such as the role of the loads characteristics, the influence of the frequency measure and the inverter regulation speed
Risk of unintentional islanding in LV distribution networks with inverter-based DGs
No full textThe number of small power Distributed Generation
(DG) units connected to the distribution networks has increased
particularly for photovoltaic (PV) applications. According to
recently issued Italian standards, each DG unit is allowed to
participate in the active and reactive power regulation, using
specifically defined P-f and Q-V droop characteristics.
Furthermore, these standards have introduced wider frequency
and voltage thresholds allowed during normal operation of DG
units. Therefore the risk of unintentional islanding operations is
expected to increase, due to the possibility of the DG units to
supply the loads with a wider voltage and frequency range
without the protections interventions. In this paper, the impact
of the loads’ voltage and frequency dependence on the isolated
grid’s frequency and voltage deviation, during unintentional
islanding operations, has been considered. The system has been
modeled and analyzed through detailed dynamics simulations.
The results show that, using a classical grid-connected inverter
control system, the loads’ voltage and frequency dependence
may play a crucial role in determining the unintentional
islanding operation and possible failure of the protections
intervention
Chapter Profilo minimo dell’opera di Riccardo Del Punta (1957-2022)
No full textThe author reconstructs and comments on the scientific production of Riccardo del Punta, examining his style, influences, lines of research, and legacy for labour law
Analysis of DP-DQ area of uncontrolled islanding in low voltage grids with PV generators
No full textChapter Capability e diritto del lavoro: non solo teoria. Dialogando con Riccardo del Punta
No full textThe paper is a tribute to Riccardo Del Punta, intellectual and jurist. The common thread is the use of Capability Approach in labour law which links the Author to his friend who passed away prematurely. The essay is also an opportunity to revisit the basic foundations of the Capability theory and the recent debate among international labour law scholars with regard to its possible use in the great transformation induced by the double (green and digital) transition
Analysis of load-induced unintentional islanding in Low Voltage grids with PV generators
No full textAnalysis of ΔP - ΔQ Area of Uncontrolled Islanding in Low-Voltage Grids With PV Generators
No full textA Simplified Algorithm for OLTC Control in Active Distribution MV Networks
No full textThe increasing penetration of Distributed
Generation (DG) in distribution electrical systems may cause
alteration of voltage profiles on the lines. Traditionally,
distribution networks with radial configuration are designed
as a passive top-down architecture where voltage regulation
is mainly performed by an On-Load Tap Changer (OLTC)
transformer located at the Primary Substation. Therefore it
becomes rather difficult to compensate lines radiating out
from the same bus-bar where some of these are subject to
overvoltages due to the power injection by DGs connected
whereas others are subject to voltage drops due to the
presence of passive loads only. A first step in regulation and
managing the voltage levels, in order to be consistent with the
contingent needs of the network, may be a decentralized local
control strategy performed by the DG units, however better
results will be obtained with a coordinated OLTC
intervention.
In this paper an OLTC control strategy, based on only few
remote measurements, is proposed. This procedure allows the
tap changer controller to infer the state of network node
voltages and to act accordingly. The performance of the
proposed control method is demonstrated through
simulations on a realistic MV distribution network
Modeling the Control of Islanded Networks Supplied by Inverters: the Case of MV and LV Systems
No full textThe increasing number of inverter-based
Distributed Generator (DG) units connected to both MV and
LV distribution networks can be used as a resource in order to
overcome some emergency conditions. The presence of
different inverter-based DG units could introduce issues
regarding the management of intentional islanded networks,
therefore reliable inverter control strategies for islanded
operation assume an essential role.
In this paper an inverter operating scheme has been
implemented suitable in presence of networks supplied by a
single DG or multiple DGs and for both grid tie and grid off
operation. This inverter control scheme has been modeled and
tested through detailed dynamic simulations in LV and MV
islanded networks. Moreover the dynamic behavior of the
proposed inverter control strategy has been studied and
analyzed in light of the recently issued Italian connection grid
codes for active users.
The results show that the control scheme allows operation
of intentional islanded networks supplied by single or multiple
DG units. In case of multiple DG units, simulations show that,
grid connection rules influence the dynamic of islanding
operations depending on the power balance existing before the
islanding forming
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