Search results for "Volt"
showing 10 items of 2187 documents
Lightning-current distribution in MV grids interconnected earthing systems
2017
The paper presents first investigations results on the effects of lightning stroke on medium voltage (MV) installations' earthing systems, connected together with the metal shields of the MV distribution grid cables. The study enables to evaluate the distribution of the lightning current among interconnected earth electrodes in order to assess if the interconnection, usually done for reducing earth potential rise during an earth fault, can give place to dangerous situations far from the installation hit by the lightning stroke. Two case studies of direct lightning stroke are presented and discussed: two interconnected MV substations of the MV grid; a high voltage/medium voltage (HV/MV) stat…
Optimizing droop coefficients for minimum cost operation of islanded micro-grids
2017
This paper shows how minimum cost energy management can be carried out for islanded micro-grids considering an expanded state that also includes the system's frequency. Each of the configurations outputted by the energy management system at each hour are indeed technically sound and coherent from the point of view of generation-consumption balancing by exploiting a frequency dependent load flow algorithm. A Glow-worm Swarm Optimization (GSO) algorithm carried out in a 24 hour time frame provides optimized results. A test has been carried out for a residential PV-Storage-Microturbine islanded micro-grid to show the feasibility as well as the efficiency of the proposed approach and results ar…
Technical and Economic Aspects of Photovoltaic Conversion of Southern Poland
2014
Abstract The article presents the results of a 13-year tests and analysis of performance and energy and electrical charge yield for typical photovoltaic modules made of different absorbers. Modules were installed on the south wall of Opole University building (at kard. B. Kominka Street). Registered in this period (2001-2013) values energy and charge of tested modules are presented in reference to 1 Wp their nominal power and to 1 m2 of PV modules. Their annual and monthly distributions, with particular emphasis on the seasonal changes of its parameters and phenomena of aging and degradation of the PV modules structure were shown. In the final part of the article was presented an economic a…
On the hazardous situations due to the presence of HV/MV substations in urban areas
2017
The paper focuses on the hazardous situations that can rise in urban areas in case of earth fault inside a High Voltage/Medium Voltage station. IEEE and IEC/EN Standards and technical documents are examined and discussed, in order to propose some practical guidelines for a safe integration of such installations in contexts characterized by the presence of low voltage systems and not trained persons.
Innovative algorithms for the management of combined RES-BESS systems
2017
The issue of the optimal management of the available energy resources also at end-user level is getting more and more attention. The paper deals with the definition of innovative algorithms for managing electrical storage systems in hybrid photovoltaic and wind plants, also taking into account different pricing periods and a grid emergency condition in which the Utility can request an injection of power by the end-user. Application examples for explaining the operation of the algorithms are presented.
Finite difference thermal model of a latent heat storage system coupled with a photovoltaic device: Description and experimental validation
2014
Abstract The use of photovoltaic (PV) systems has been showing a significant growth trend but for a more effective development of this technology it is essential to have higher energy conversion performances. Producers of PV often declare an higher efficiency respect to real conditions and this deviation is mainly due to the difference between nominal and real temperature conditions of the PV. To improve the solar cell energy conversion efficiency many authors have proposed a methodology to keep lower the temperature of a PV system: a modified PV system built with a normal PV panel coupled with a Phase Change Material (PCM) heat storage device. In this paper is described a thermal model ana…
Oil filled MV/LV Power Transformer Behavior in Narrow Band Power Line Communication Systems
2012
The aim of this paper is to characterize oil-filled power transformers in the narrow-band power-line communication (PLC) frequency range of 50-150 kHz. A new model is proposed for such type of a transformer, in the aforementioned frequency range of interest, in order to study its influence on the signal transmission and to investigate the possibility that the PLC signal can cross the power transformer itself. The new model is simpler than those previously proposed in literature, and it can be used in the whole frequency range available for NB PLC according to the CENELEC EN 50065-1 A-band. In order to validate the model, simulation and measurement results are compared for four oil-filled po…
An Innovative Measurement Approach for Load Flow Analysis in MV Smart Grids
2016
This paper proposes a novel measurement procedure for load flow analysis in medium voltage (MV) smart grids. The new approach is based on power measurements at low voltage (LV) side of MV/LV distribution substations. Such measurements are carried out by means of power quality analyzers. If compared with the load flow methods based on measurements at the MV side, the proposed approach has a lower cost and it offers an equally reliable measurement system. The proposed algorithm takes the basic concept of the current summation backward/forward method; some modifications are introduced to use LV load powers measurements. To this aim, the MV/LV power transformer is properly modeled and taken int…
A New Low Cost Coupling System for Power Line Communication on Medium Voltage Smart Grids
2018
This paper proposes and verifies the performance of an innovative and low cost coupling system for power line communication (PLC) on medium voltage (MV) smart grids. The coupling system makes use of the capacitive divider of the voltage detecting systems (VDSs) to inject and receive the PLC signal. VDS are usually already installed in the MV switchboards of the major electrical manufacturer all over the world according to IEC 61243-5. VDS are used to detect the presence of the mains voltage to guarantee personnel safety. An interface circuit has been developed to be connected between the PLC transceiver and the VDS socket. In this way, the PLC signal can be coupled to the MV network without…
Decoupled control scheme of the grid-connected split-source inverter for renewable energy sources
2016
Grid-connected power conversion systems for renewable energy sources must fulfill several requirements, including high efficiency, reduced cost and complexity, and, quite often, also boost capabilities from the dc sources to the ac power grid. For such applications, single-stage power converters with boost capabilities offer some potential advantages. Among several proposed options, split-source inverter (SSI) has been recently investigated. This paper proposes a decoupled control scheme for the SSIs, where the common mode term of the ac modulation signals is used to control the dc input current. Thus, the dc input current and ac output current can be controlled independently. The proposed …