A prototypal architecture of a IEEE 21451 network for smart grid applications based on power line communications

This paper deals with the development of reliable measurement and communication devices and systems and their integration on a prototypal network architecture for smart grid applications, based on the use of narrowband power line communications (PLCs). The proposed solution is presented and discussed in the framework of the ISO/IEC/IEEE 21451 family of Standards. Currently, PLCs are not properly addressed by the aforesaid Standards; on the other hand, by including such issue, their guidelines could represent a common platform for the integration and interoperability of the proposed systems and devices. This would allow to exploit the benefits of the IEEE 21451 approach also for PLC-based sm…

A New Coupling Solution for G3-PLC Employment in MV Smart Grids

This paper proposes a new coupling solution for transmitting narrowband multicarrier power line communication (PLC) signals over medium voltage (MV) power lines. The proposed system is based on an innovative PLC coupling principle, patented by the authors, which exploits the capacitive divider embedded in voltage detecting systems (VDS) already installed inside the MV switchboard. Thus, no dedicated couplers have to be installed and no switchboard modifications or energy interruptions are needed. This allows a significant cost reduction of MV PLC implementation. A first prototype of the proposed coupling system was presented in previous papers: it had a 15 kHz bandwidth useful to couple sin…

Measurement Issues for the Characterization of Medium Voltage Grids Communications

This paper is focused on the measurement issues and procedures for the characterization of medium voltage grids for narrowband power line communications (NB-PLCs), in the perspective of the use and integration of such technology into smart grids communication networks. The fundamentals are given for the characterization of the PLC channel, by means of noise and attenuation measurements. Suitable procedures are also developed for the characterization and modeling of the power system components in the frequency range of interest. Furthermore, the complete model of the PLC system is experimentally validated in a real case study.

Experimental Evaluation on Narrow Band Power Line Communication in Medium and Low Voltage Smart Grids

The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid and energy storage applications. More in detail, this paper deals with one of the most important issues on this topic, which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After an analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means …

Current transformers effects on the measurement of harmonic active power in LV and MV networks

The harmonic active power is used to determine the location of polluting loads, the direction of harmonic power flow and to estimate how consequential a certain current harmonic source is. The highest uncertainties, when measuring harmonic active power, are introduced by the current and voltage transducers. This paper presents experimental results which show the impact of current transformers (CTs) on the accuracy of the harmonic power measurements. An expression for the evaluation of the power error in distorted conditions was developed which can be easily utilized in the case of linear current transducers. It is shown how CTs cannot be considered linear transducers and how the higher the …

Characterization and Error Compensation of a Rogowski Coil in the Presence of Harmonics

This paper reports the results of an experimental study dealing with a commercial Rogowski coil current transducer (RCCT) in the presence of harmonic distortion. The RCCT was observed under two conditions: 1) sinusoidal excitation with frequencies from 50 to 750 Hz and 2) nonsinusoidal excitation using fundamental frequency and one harmonic, with adjustable amplitude and phase shift. The experimental results show only a weak dependence of the harmonic current ratio error and phase displacement on the amplitude and phase shift of the excitation harmonic. The phase displacement is also independent of the conductor position within the Rogowski coil window. An error compensation method, based o…

Real-Time Power Flow Monitoring and Control System for Microgrids Integration in Islanded Scenarios

This article presents an enhanced system for real-time power flow monitoring and control (PFMC) for microgrids integration in medium-voltage (MV) distribution networks. The developed solution includes both system architecture and the monitoring and control algorithms, and it has low implementation and installation costs. It is based on the use of hardware and software solutions previously proposed by the authors, i.e., a distributed measurement, a control and communication architecture, and a supervisory control and data acquisition (SCADA) software, which have been enhanced and integrated for the considered application. The SCADA implements a load flow (LF) algorithm for real-time power fl…

Medium Voltage Smart Grid: Experimental Analysis of Secondary Substation Narrow Band Power Line Communication

This paper is focused on the possibility of employing narrow band power line communication (PLC) in medium voltage (MV) distribution networks. The topic is investigated by means of both simulations and experimental tests, which were carried out in the distribution network of Ustica Island. In detail, a two-way MV communication was tested between two secondary substations connected by an MV cable power line. Each substation has a by-pass connection at MV bus-bars and an MV/LV oil filled power transformer. In this paper, the MV and the PLC systems under test are described and the experimental tests are presented, which were carried out to evaluate the parameters of the simulation model. The a…

A PC-based wattmeter for accurate measurements in sinusoidal and distorted conditions: Setup and experimental characterization

This paper presents the development of a high-accuracy sampling wattmeter, which can be employed with both sinusoidal and distorted input signals. The proposed personal computer (PC)-based system is a simple, portable, and low-cost solution because it is based on two commercial data acquisition boards connected to a common PC. Owing to this solution, the voltage is sensed directly, avoiding expensive voltage dividers, while the current is sensed by means of a noninductive current shunt. Commercial software is also used for data processing and implementation of the virtual instrument. The setup of the PC-based wattmeter is described, with a detailed description of the correction strategy of …

Improvement of Hall Effect Current Transducer Metrological Performances in the Presence of Harmonic Distortion

The performance of Hall effect current transducers (HECTs), under distorted waveform conditions, is usually characterized by means of a frequency response test. In this paper, it was investigated if frequency response is able to correctly evaluate the ratio and the phase errors under distorted conditions. Two HECTs, with the accuracy class level of 1% and 0.5%, respectively, were experimentally characterized under two conditions: 1) sinusoidal excitation with frequencies ranging from 50 to 750 Hz, which is the well-known frequency response test, and 2) nonsinusoidal excitation using fundamental frequency and one harmonic with adjusted amplitude and phase shift. It was found that ratio and p…

Characterization of clamp-on current transformers under nonsinusoidal conditions

This paper reports the performance of clamp-on current transformers under nonsinusoidal conditions. A set of experimental measurements helped to determine the ratio and the phase errors under two conditions: 1) sinusoidal excitation with frequencies from 45 to 1000 Hz and 2) nonsinusoidal excitation using the fundamental frequency and one harmonic, with adjusted phase shift. It was found that ratio and phase errors are affected by the phase angle between the harmonic and the fundamental and the harmonic amplitude. The effects of conductor location in the current transformer's window and of the air-gap width were also investigated. It was concluded that harmonic phase and ratio errors measur…

A Line Impedance Calculator Based on a G3 PLC Modem Platform

Power line communication (PLC) is one of the most today used technologies for both automatic meter reading and many other smart grid applications. In this framework, a characterization of the electrical network in the PLC frequency range is needed in terms of impedance measurement and received signal level. This can allow choosing the most suitable and less noisy frequency ranges for PLC transmission. Usually, these characterization measurements are performed with dedicated instrumentation and in the absence of mains voltage. This article wants to propose an alternative solution, which allows these kinds of measurements to be performed using electronic boards currently used as on-field appl…

Smart interface devices for distributed generation in smart grids: The case of islanding

With the increasing presence of distributed generators (DGs), the implementation of a smart sensors and actuators network in distribution grids has become crucial for different monitoring, management and protection functionalities. For DGs monitoring and control, sensors and actuators are usually embedded in so-called interface devices (IDs) or interface protection systems (IPSs). Existing IDs lack in communication interfaces both to the electrical energy Distribution System Operators (DSOs) and to the DGs inverter. In this framework, the authors have developed a new ID solution and a proper communication architecture, which allow implementing new smart functionalities based on the interact…

Arc Fault Detection Method Based on CZT Low-Frequency Harmonic Current Analysis

This paper presents a method for the detection of series arc faults in electrical circuits, which has been developed starting from an experimental characterization of the arc fault phenomenon and an arcing current study in several test conditions. Starting from this, the authors have found that is it possible to suitably detect arc faults by means of a high-resolution low-frequency harmonic analysis of current signal, based on chirp zeta transform, and a proper set of indicators. The proposed method effectiveness is shown by means of experimental tests, which were carried in both arcing and nonarcing conditions and in the presence of different loads, chosen according to the UL 1699 standard…

An Innovative Coupling Solution for Power Line Communication in MV Electrical Networks

One of the main problems in the diffusion of power line communication (PLC) in medium voltage (MV) networks is the need of a dedicated PLC coupler to be installed all over the network. To avoid this problem, the authors have studied, prototyped and patented an innovative PLC coupling solution which uses electrical elements embedded in most of the switchgears already installed in MV networks, i.e. the capacitive dividers of the voltage detecting systems (VDS). The new solution prototype is described in this paper, highlighting the advantages in terms of a significant reduction of both direct costs of equipment and infrastructures and indirect costs of installation and service interruption. T…

Comparison of two different approaches for harmonic distortion sources assessment

The paper focuses the attention on the comparison of two approaches for power quality assessment in the electric grid. Both approaches are suitable for investigating the harmonic pollution source and discovering if the harmonic source comes from the customer or the utility grid. The two approaches have the same purpose but they are deeply different. The first approach is based on the knowledge of the customer and utility equivalent impedance while the second is based on single point measurement at point of common coupling PCC. In this paper, the advantages and drawbacks of the two approaches are investigated also supported by a case study.

Realizzazione di un banco di misura e di un modello in Simulink per la ricerca e la caratterizzazione di reti di accoppiamento per la trasmissione di segnali su cavi di media tensione

A resilient distributed measurement system for smart grid application

Since the production of energy from renewable energy sources is strongly increasing, the migration from the classical electric grid toward the smart grid is becoming a reality. Distribution System Operators, along with the control of the entire network and its stability, need to address the security and the reliability of the communication channels and the data itself. In this paper a solution is proposed to address these issues. It is based on a distributed measurement system that relies on a wireless network as well as a redundant Power Line communication system in order to transfer the electrical measures to a centralized SCADA server. The collected data are used to run a power flow algo…

Experimental EMF characterization of a secondary substation

This paper presents the results of the experimental EMC characterization of a new medium/low voltage (MV/LV) secondary substation, which was developed in the framework of the research project "NEW CAB ELARC". It has two MV/LV transformers, with total rated power of 1000 kVA. To perform the experimental characterization, firstly an analysis was performed of the Italian and European standards recommendations. Different approaches were highlighted and the most appropriate procedures were identified for the measurement of the magnetic fields emissions, at power systems frequency (50 Hz) in steady-state conditions. A dedicated test lab was set up for the secondary substation characterization. Th…

Characterization of DC series arc faults in PV systems based on current low frequency spectral analysis

Abstract This work presents an experimental study focused on the characterization of series arc faults in direct current (DC) photovoltaic (PV) systems. The aim of the study is to identify some relevant characteristics of arcing current, which can be obtained by means of low frequency spectral analysis of current signal. On field tests have been carried out on a real PV system, in accordance with some tests requirements of UL 1699B Standard for protection devices against PV DC arc faults. Arcing and non-arcing current signals are acquired and compared and the behavior of a set of indicators proposed by authors is analyzed. Different measurement equipment have been used, in order to study th…

Comunicazione power line in reti di media e bassa tensione: modellizazione e verifiche sperimentali

Development of a high-accuracy PC-based wattmeter with commercial data acquisition boards

This paper presents the development of a high accuracy sampling wattmeter, which makes use of two commercial data acquisition boards (DAQs) connected to a common personal computer. Commercial software is also used for data processing and implementation of the virtual instrument. The set up of the PC-based wattmeter is described and a preliminary evaluation of its metrological performances is made by means of two series of experimental tests, which were carried out with an electric power standard and a high performance multifunction calibrator. © 2011 IEEE.

High-Frequency Experimental Characterization and Modeling of Six Pack IGBTs Power Modules

In this paper, a method to characterize the high-frequency (HF) behavior of six pack insulated gate bipolar transistors (IGBTs) power module (PM) is presented. The method is based on experimental measurements at the external pins of the device and it allows one to extract internal inductive and capacitive parasitic coupling without the knowledge of structural and physical parameters of the PM. The HF model of a six pack IGBTs PM has been developed, in the frequency range of 150 kHz-30 MHz, and it has been implemented in MATLAB environment. The method has been experimentally validated by comparing the frequency behavior of the PM with the simulated response. Moreover, the HF conducted distur…

CZT-Based Harmonic Analysis in Smart Grid Using Low-Cost Electronic Measurement Boards

This paper validates the use of a harmonic analysis algorithm on a microcontroller to perform measurements of non-stationary signals in the context of smart grids. The increasing presence of electronic devices such as inverters of distributed generators (DG), power converters of charging stations for electric vehicles, etc. can drain non-stationary currents during their operation. A classical fast Fourier transform (FFT) algorithm may not have sufficient spectral resolution for the evaluation of harmonics and inter-harmonics. Thus, in this paper, the implementation of a chirp-Z transform (CZT) algorithm is suggested, which has a spectral resolution independent from the observation window. T…

Experimental investigation on PLC signal crossing of power transformers

In this work the use of PLC in MV-LV networks is investigated, by means of experimental tests in the case of a two-ways MV/LV communication between two secondary substations. The two substations are connected by a MV overhead power line. Moreover each substation has a by-pass connection at MV bus-bars and a MV/LV power transformer. A ST7580 transceiver is used to inject the communication signal. The transceiver is embedded in a new interface device developed by the authors. In the paper the communication issues are introduced and some experimental tests are presented and discussed. Such tests have been carried out in the presence of voltage net, i.e. 24 kV, with the aim to verify the possib…

An Innovative Measurement Approach for Load Flow Analysis in MV Smart Grids

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…

Strumento virtuale in ambiente LabVIEW per la gestione automatica di misure di emissione radiata in camera semianecoica

NB PLC and Software Defined Networking for Smart Grid Applications

During the last years, the installation of Distributed Energy Resources (DERs) and the expected diffusion of Electrical Vehicles (EVs), is increasing the complexity of the distribution grid, making the management of the grid operated by Distribution System Operators (DSOs) more difficult. The Smart Grid approach tries to provide a response to these troubles, by means of a strong interaction between the power grid and Information and Communication Technology (ICT) infrastructures. The drawback of this approach is an increase in the management effort of the ICT infrastructures, for which the DSO are not prepared. Software Defined Networking (SDN) is an approach developed to manage complex ICT…

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

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…

An Improved Load Flow Method for MV Networks Based on LV Load Measurements and Estimations

A novel measurement approach for power-flow analysis in medium-voltage (MV) networks, based on load power measurements at low-voltage level in each secondary substation (SS) and only one voltage measurement at the MV level at primary substation busbars, was proposed by the authors in previous works. In this paper, the method is improved to cover the case of temporary unavailability of load power measurements in some SSs. In particular, a new load power estimation method based on artificial neural networks (ANNs) is proposed. The method uses historical data to train the ANNs and the real-time available measurements to obtain the load estimations. The load-flow algorithm is applied with the e…

An interface protection system with power line communication for distributed generators remote control

The aim of this work is to present a narrow band power line communication (NB-PLC) interface protection system (IPS) for distributed generators (DGs); it has been developed according to the current standard CEI 0-21 and the requirements for smart grid applications. For such applications, the new IPSs have to implement new intelligent functions such as remote monitoring and control of DGs and Energy Storage Systems (ESSs) inverters, not only in terms of disconnection but also of voltage regulation and power modulation by the utility control. The main feature of the developed IPS is the ability to interact with both the grid and the DG's and ESS's inverters. In fact, it can communicate with t…

Un metodo ibrido per il riconoscimento dell'islanding in reti di media e bassa tensione in presenza di generazione distribuita

Characterization of IP-Based Communication for Smart Grid Using Software-Defined Networking

The smart grid (SG) approach is based on a strong interaction between the network communication infrastructure and the power grid. Usually the management of the infrastructure is done by the distribution system operators (DSOs) that are worried about the increasing managing complexity due to the presence of increasing number of distributed energy resources and electrical vehicles. The use of software-defined networking (SDN) may simplify the network configuration and management for DSO, as highlighted from previous research works. The objective of this paper is to introduce and characterize an internet protocol (IP)-based communication architecture with specialized SDN bridges operating als…

An Experimental Characterization of Time of Arrival Accuracy for Time Synchronization of Medium Voltage Smart Grid Solutions

The time synchronization of smart grid devices is a critical feature for the successful application of advanced grid monitoring and control techniques. Synchronization mechanisms based on the accurate estimation of the Time of Arrival (ToA) of network messages - sent over power line cables - are a promising solution to achieve synchronization tasks over distribution lines. In this paper, a chirp-based synchronization technique over the Medium Voltage (MV) grid has been proposed and characterized. Such approach has the benefit of not requiring the installation of a dedicated infrastructure, thanks to the exploitation of power distribution lines for the transmission of time synchronization da…

Caratterizzazione metrologica di trasduttori di corrente in presenza di distorsione armonica

A New Low Cost Coupling System for Power Line Communication on Medium Voltage Smart Grids

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…

Frequency response of Measurement Current Transformers

In this paper the frequency response of two CTs is experimentally evaluated in the range of 30-600 Hz. A theoretical analysis of CTs behavior has been developed by means of the equivalent circuit. It was shown, by an experimental test, that, for the frequency range analyzed, the transformer equivalent circuit is a valid tool for the evaluation of CT performances.

Design and Characterization of a New MV PLC Coupler for Smart Electric Energy Systems

This paper deals with the design, modeling and characterization of a new coupling system for medium voltage (MV) narrow band power line communications (NB-PLC). It exploits the capacitive divider of voltage detecting systems (VDSs) normally used to reveal the mains voltage presence, thus avoiding the use of dedicated MV couplers. The proposed coupling system was patented by the authors. In this paper, the modeling of the VDS capacitive divider is presented, using a proper characterization method. Moreover, the interface card design is described, based on simulation of the whole PLC transmission channel. Laboratory tests are also presented and discussed. More in detail, a frequency response …

Hall Effect Clamp-on Current Transducer Characterization under Nonsinusoidal Conditions

Implementation of a Management System for Prosumer Energy Storage Scheduling in Smart Grids

Scheduling of energy storage systems of distributed generation is a key element for optimal renewable energy sources (RES) exploitation in smart grids, demand side response strategies implementation and prosumers interaction with Distribution System Operators (DSOs). In this context, this paper presents the implementation of a management system for energy storage scheduling, which allows taking appropriate account of the storage system behavior in real cases. To properly consider the real system operation, the employed battery model is modified, in order to include also the hysteresis phenomena in state of charge estimation in both charging and discharging operation. The validation of the p…

A PC-based wattmeter for high accuracy power measurements

This paper proposes the use of a commercial data acquisition board (DAQ) connected to a common personal computer for high accuracy power measurements. In the paper the set up of the PC-based wattmeter is described and an experimental evaluation of its metrological performances is made by means of the comparison with a simultaneous coherent digital sampling wattmeter realized with two high-precision DMMs Hewlett Packard Model 3458 A. In both cases the power source is a Fluke 6100A/E electrical power standard. © 2010 IEEE.

A simplified approach for load flow analysis in MV smart grids based on LV power measurements

This paper presents a simplified approach for load flow analysis in medium voltage (MV) distribution networks. It is a power summation Backward/Forward (B/F) algorithm, based on measurements of active and reactive powers at low voltage (LV) side of MV/LV distribution substations. The proposed solution allows achieving good accuracy, computational efficiency and fast convergence. In order to verify the algorithm performances, simulation studies are carried out in the case of a real test system, i.e. the distribution grid of Favignana Island (Mediterranean Sea, Italy). The compatibility between simulations results and power measurements at the MV bus bars of the generating substation shows th…

Simulation of a Power Line Communication System in Medium and Low Voltage Distribution Networks

The aim of the paper is to study the influence of the power transformer on signal transmission in the case of a power line communication (PLC) system in a overhead Medium Voltage (MV) power network. A model of the PLC system was carried out by means of the Simulink® software. A distributed parameter MV overhead line, two power transformers, the signal coupling networks and the receiving and transmitting line coupling interface of a ST7540 FSK powerline transceiver were included in the model. The performances of the complete PLC communication system are evaluated for different line lengths by means of the attenuation computed as ratio between the received and transmitted voltage signals.

Innovative Solutions for the Integration of Renewable Energies on Tunisian and Sicilian Electrical Grids

The rapid spread of distributed generation from renewable energy sources, combined with their unpredictable behavior, requires the continuous monitoring and control by the Distribution System Operator, in order to guarantee the stability and efficiency of the distribution network. Thus, in this paper a new measurement and communication architecture is proposed, which foresees the use of innovative devices and different technology-oriented solutions, even redundant ones, which allows the transition from passive to active electricity distribution network, with minimal structural changes. The architecture has been developed in the framework of the SInERT project (Italy-Tunisia cross-border coo…

Realizzazione in ambiente LabVIEW di un sistema automatico di gestione della cella GTEM per prove di compatibilità elettromagnetica

High frequency modeling technique for three phase power electronics module

Nowadays, the high integrated power electronics modules (PMs), characterized by high speed, low loss and hard ware miniaturization, represent a new technology that meets the emerging demands of many applications, such us vehicle and home appliance, renewable energy sources in smart grid. The integration process and the high switching speeds increase the PM electromagnetic emissions that can create electromagnetic interference (EMI) with electric/electronic devices near the PMs. For this reason, electromagnetic compatibility (EMC) have to be carefully considered, yet in the design phase, to guarantee the reliability of PM systems. In this paper a method to develop a high frequency (HF) model…

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

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…

Un wattmetro basato su schede di acquisizione commerciali per misure in regime distorto. Sviluppo dello strumento e prove preliminari

LV Measurement Device Placement for Load Flow Analysis in MV Smart Grids

This paper deals with the issue of measurement device placement for load flow analysis in medium-voltage (MV) distribution networks. The study is carried out using an innovative measurement algorithm for load flow analysis developed by the authors. It is based on low-voltage (LV) load power measurements applied on a backward/forward algorithm for the load flow resolution. The final aim is to identify the most suitable number and placement of the LV measurement points in order to limit the uncertainty on the power flow estimation to a target value. The proposed approach is based on the uncertainty evaluation of the estimated power flows; a sensitivity analysis is performed in order to assess…

Enhanced islanding detection in smart interface protection systems of distributed generation

The widespread presence of distributed generators (DGs) and storage systems (DSSs) in electricity grids has increased the risk of islanding occurrence. This phenomenon must be suitably managed by Distribution System Operators (DSO), in order to avoid adverse situations, in terms of grid-protection problems, equipment damage, safety hazards, power quality problems and so on. Currently anti-islanding protection functions are handled by interface protection systems (IPSs), which are built in accordance with relevant standards for DGs and DSSs connection to power systems. However, some problems may occur in case of operation within the so-called non detection zone (NDZ). This paper presents an …

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

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…

Implementation and Experimental Tests of a Management System for MV/LV Distribution Grids

The continuous monitoring of network power flows and the remote control of Distributed Generators and Energy Storage Systems are the essential elements to allow a full exploitation of Renewable Energy Sources and their real integration in distribution networks. Thus in the paper a management system is presented for load flow monitoring in MV/LV distribution network. Moreover, on the basis of calculated power flows, the management system is able to send control commands to DGs and ESSs, to vary their power production or power factor or eventually to disconnect them in order to maintain the network stability. The proposed solution was really implemented in the MV network of Ustica Island, dev…

Electromagnetic immunity analysis of a new interface device with power line communication for smart grid and energy storage applications

An analysis of EMC standards related to smart grid devices with PLC port has been carried out and the standardization lacks have been pointed out with reference to the evaluation of electromagnetic immunity to narrowband, coming from other communication systems connected to the grid, and RF disturbances conducted disturbances, usually present in a power grid. In particular, the paper analyses the electromagnetic conducted immunity of a new interface protection device (ID) for smart grid and energy storage applications. The new ID is equipped with a measuring board, a STM32 microcontroller, for data elaboration and memorization, and a ST7580 N-PSK powerline transceiver. An experimental test …

A new method for forecasting energy output of a large-scale solar power plant based on long short-term memory networks a case study in Vietnam

Abstract This paper proposes a new model for short-term forecasting power generation capacity of large-scale solar power plant (SPP) in Vietnam considering the fluctuations of weather factors when applying the Long Short-Term Memory networks (LSTM) algorithm. At first, a configuration of the model based on the LSTM algorithm is selected in accordance with the weather and operating conditions of SPP in Vietnam. Not only different structures of LSTM model but also other conventional forecasting methods for time series data are compared in terms of error accuracy of forecast on test data set to evaluate the effectiveness and select the most suitable LSTM configuration. The most suitable config…

IEEE Std 1459–2010. IEEE Standard Definitions for the Measurement of Electric Power Quantities under Sinusoidal, Nonsinusoidal, Balanced or Unbalanced Conditions

Definitions used for measurement of electric power quantities under sinusoidal, nonsinusoidal, balanced, or unbalanced conditions are provided in this standard. Mathematical expressions that were used in the past, as well as new expressions, are listed, as well as explanations of the features of the new definitions.

An interface protection system based on an embedded metrology system platform

Abstract The aim of this work is to present an interface protection system (IPS) for Distributed Generators (DG) and Energy Storage Systems (ESS). The new prototype of IPS guarantees standard protection requirements, in terms of both voltage and frequency measurement accuracies and trip times. Moreover, it has the additional functionalities of implementing a communication link between the Distribution System Operator (DSO) and the DG and ESS Inverter. The new IPS is based on a smart meter platform with an integrated power line communication modem. Moreover, it has also an integrated metrology section. Experimental tests will show how this last feature allows a significant reduction of the m…

On the use of narrow band power line as communication technology for medium and low voltage smart grids

The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid applications. More in detail, this paper deals with one of the most important issues on this topic which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After a analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means of simulations and ex…

Model of line to shield power line communication system on a Medium Voltage network

In this paper a complete model of a power line communication (PLC) system on a Medium Voltage (MV) network is presented in the case of a line-ground configuration. A simple and friendly Simulink (R) software is used to develop the model. A distributed parameter MV cable model in line-ground configuration is considered together with the power transformers, the signal coupling networks and the receiving and transmitting line coupling interface of a ST7540 FSK powerline transceiver. The performances of the complete PLC communication system are evaluated for different line lengths by means of the attenuation computed as ratio between the received and transmitted voltage signals.

A DAQ-based sampling wattmeter for IEEE Std. 1459-2010 powers measurements. Uncertainty evaluation in nonsinusoidal conditions

Abstract This paper presents the evaluation of the metrological performances of a DAQ-based sampling wattmeter (DAQ-SW) for the measurement of IEEE Std. 1459-2010 power quantities in non-sinusoidal conditions. The instrument makes use of two commercial data acquisition (DAQ) boards, a non-inductive current shunt, a personal computer and a commercial software for data processing. Starting from the results of an experimental characterization of the two instrument channels with non-sinusoidal voltages and currents and a correlation analysis, the combined standard uncertainties of IEEE Std. 1459-2010 quantities are evaluated, following the approach of the ISO Guide to the Expression of Uncertai…

A new low cost power line communication solution for smart grid monitoring and management

Modern smart grids require the improvement of measurement and communication infrastructures of distribution networks, at both medium voltage (MV) and low voltage (LV) levels. Distributed sensing and measurement systems are needed to provide all necessary data for grid monitoring, control and management, as well as for the implementation of a number of smart functionalities, such as remote control of distributed generators (DGs), real time analysis of power flows, automatic meter reading (AMR), demand side management (DSM), grid automation and so on [1]-[6]. Acquired network data include typical electrical network quantities and status variables (such as powers, voltages, currents, switches …

A back to back method for the temperature rise test of prefabricated substations: A case study

In this work a back to back method is presented which allows to develop heating tests of prefabricated secondary substations with a limited number of supplying equipment (an induction regulator and a capacitor bank). The proposed method makes use of the transformer tap changers to create a voltage difference on the medium voltage side. In this way, only an adjunctive low voltage supply is needed. With the proposed test system, the heating tests are developed on a 1000 kVA prefabricated substation. Thanks to the experimental tests, the class of enclosure of the substation and the operating temperature and resistance of the power transformers are determined, according to the recommendations o…

Experimental evaluation of an hybrid communication system architecture for smart grid applications

In this paper a new communication system architecture is proposed for the development of a SCADA system which can remotely monitor and control intelligent electronic devices (IEDs) connected to the low voltage distribution networks, i.e low voltage smart meter (SM), interface protection devises (IPS). New distributed metering systems and interface devices, together with a proper communication infrastructure (HiperLAN and narrowband power line communication (NB-PLC) on low voltage network), have been developed to allow monitoring the whole power system and controlling the distributed generators of a Smart Grid also in the presence of harmonic distortions. In this way, the electrical energy d…

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

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…

Un approccio semplificato per il calcolo del load flow nelle smart grids basato su misure distribuite in bassa tensione

I sistemi di misura distribuiti sono alla base delle "smart distribution grids", ove la crescente presenza di generazione distribuita e sistemi di accumulo e la conseguente transizione verso sistemi attivi rendono necessarie funzionalità avanzate di monitoraggio, controllo e gestione delle reti. In tale contesto, un elemento essenziale è l'analisi dei flussi di potenza, che, com'è noto, può essere effettuata tramite algoritmi di load flow, noti il modello della rete e le potenze generate/assorbite nei vari nodi. Per la misura di tali grandezze sulla media tensione (MT), si possono utilizzare diversi strumenti (quali phasor measurement units, smart meters, power quality analyzers), che però …

Sistema di misura per l’analisi spettrale di segnali non stazionari: implementazione in VHDL per lo sviluppo di un prototipo su FPGA

Compensation of Nonlinearity of Voltage and Current Instrument Transformers

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…

Uncertainty evaluation of a Backward/Forward Load Flow algorithm for a MV smart grid

This paper presents the uncertainty evaluation of an innovative measurement algorithm for load flow analysis in MV distribution networks. The measurement procedure is based on Low Voltage (LV) load power measurements applied on a Backward/Forward (B/F) algorithm for the Load Flow (LF) resolution. Furthermore, in the procedure a three phase voltage measurement at the MV generating substation bus-bars is also considered. The accuracy analysis of the LF algorithm is performed in the case of a real load condition in the distribution grid of Ustica island, Italy. The analysis takes into account the uncertainty of the measurement instruments at the LV side of each secondary substation power trans…

A Monitoring and Management System for Energy Storage Integration in Smart Grids

The integration of distributed storage systems (DSSs) at users and prosumers level can significantly contribute to energy efficiency and increase profits from renewable energy exploitation, thanks to suitable scheduling of charging and discharging periods. On the other hand, to preserve network stability and secure operation, Distribution Systems Operators (DSOs) are interested in DSSs control and cooperation with the grid. In this framework this work proposes a simple monitoring and management system for DSSs scheduling and its integration in a distributed measurement and control system architecture for smart grids. In the paper the proposed algorithm is tested on a simple case study at ho…

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

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…

Caratterizzazione delle pinze amperometriche ad effetto hall in presenza di distorsione armonica

PQ Metrics Implementation on Low Cost Smart Metering Platforms. A Case Study Analysis

The increasing interest on the quality of the energy supplied and generated in distribution networks is raising the need of distributed power quality (PQ) measurements. To allow such capabilities with cost effective metering solutions, this paper wants to investigate the feasibility of using smart meters, already installed for energy billing, also for power quality monitoring. To this aim, an electronic board (based on STCOMET metrology device), already used in many energy meters of different countries, has been selected as case study platform. The manufacturer firmware of this board was essentially aimed at implementing energy meter metrics and power line communications functionalities. In…

Power-Line Communication in Medium-Voltage System: Simulation Model and Onfield Experimental Tests

The aim of this paper is to develop a complete model of a power-line communication (PLC) system operating on a medium-voltage (MV) network. The core-shield configuration was chosen for signal transmission in the power cables. In order to validate the developed model experimental, the medium-voltage network of the Favignana island was used to carry out detailed testing. The transmission was performed between two transformer substations in the presence of mains voltage (i.e., 24 kV). ST7540 FSK power-line transceivers, together with capacitive coupling interfaces, were used for the transmission and the reception of the communication signal. The correlation between the experimental measurement…

Narrowband power line communications for medium voltage smart grids

The aim of the paper is to show how narrowband power line communications (NB-PLCs) can be a valid solution for medium voltage grids. Advantages and drawbacks of this solution are analyzed, starting from some experimental communication results, which were carried out on the medium power system networks of the islands of Ustica and Favignana, in the presence of the net voltage. Furthermore, some communication architectures and hardware prototypes based on NB-PLCs are proposed for different smart grids applications.

Critical issues and future prospects of the secondary substation in smart grid context

This paper is focused on the new role of the secondary substation in the smart grids context. This innovative view has been proposed and developed in the framework of two Research Projects: NewCabELARC Project and Reipersei Project. The latter provides a concrete and comprehensive low cost solutions for the smart grid monitoring and control, allowing the real diffusion and integration of Distributed Generation and the full exploitation of Renewable Energy Sources. In this field, this paper shows how the secondary substation (SS) takes the role of smart transducer node where innovative devices can be located, collecting the measurement data coming from the field devices (power and energy met…

A novel approach to current transformer characterization in the presence of harmonic distortion

The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the e…

Comportamento dei trasformatori MT/BT in sistemi di comunicazione power line. Caratterizzazione e modellizzazione

Simulation and laboratory experimental tests of a line to shield medium voltage power line communication system

A complete model of a power-line communication (PLC) system on a medium-voltage (MV) network in the case of a line-shield configuration is presented in this paper. An MV cable model in a line-shield configuration is considered together with the power transformers, the signal coupling networks, and the receiving and transmitting line coupling interface of a ST7540 FSK power-line transceiver. Simulations of the complete model of the system under consideration have been carried out for different line lengths, with and without power transformers and derivation branches. The model is validated by experimental tests performed in the laboratory. The measured results confirm the reliability of the …

A PLC based monitoring and remote control architecture for Distributed Generation and Storage systems in LV smart grids

(Abstract) This paper proposes a new power line communication (PLC) architecture for monitoring and remote control of Distributed Generators (DG) and Energy Storage Systems (ESS) connected to low voltage distribution networks. The final aim is to improve the performance of the PLC link in terms of robustness and efficiency in devices addressing. The proposed solution is based on a concentrator, to be installed in secondary substation, and a new PLC bridge, to be linked both to inverters and interface protection systems of DGs or ESSs. In this way, a communication link is obtained between distribution system operator (DSO) and DG or ESS owners. The proposed system is able to provide advanced…

Development of a Coupling System for Medium Voltage Power Line Communication in the CENELEC A Frequency Band

In this paper the performances of a new power line communication (PLC) coupling system for medium voltage (MV) smart grids are investigated in the CENELEC A frequency band (i.e. 3 - 95 kHz). The new coupling solution is based on the use of the capacitive divider of the voltage detecting system (VDS) as PLC coupler to the MV network. According to IEC 61243-5, VDS are worldwide used to reveal the presence of the mains voltage to ensure the safety of the operators. A proper interface circuit has been invented and patented to couple the PLC signal through the VDS. In this way no dedicated MV PLC coupler is required, thus avoiding the related costs of the coupler, of its installation, and those …

Measurement of Simplified Single- And Three-Phase Parameters for Harmonic Emission Assessment Based on IEEE 1459-2010

This article investigates the feasibility of using a simplified approach, based on the measurement of power ratio parameters, for harmonic emissions assessment at the point of common coupling (PCC). The proposed approach comes from the common concept of power factor correction and the definitions of the IEEE Std. 1459-2010, where line utilization and harmonic pollution levels are evaluated by means of ratios between the power quantities of the apparent power decomposition. In addition to the IEEE Std. 1459–2010 indicators, in this article, the behavior is studied of additional parameters that are conceptually similar to those defined by the IEEE Std. 1459-2010. The suitability of such param…

Rogowski coil current transducer compensation method for harmonic active power error

Abstract In the harmonic active power measurement, the highest uncertainties are generally introduced by the current and voltage transducers. In a previous paper, the authors showed that the current transformer (CT) can introduce significant errors in such measurement, especially if the phase shift between voltage and current is close to ±90°. In such condition the errors on harmonic power measurement are mainly due to the CT phase displacement. This paper shows that better results can be achieved with more linear transducers, such as the Rogowski coil current transducers (RCCTs), whose metrological performance in distorted condition can be improved, by means of a proper compensation method…

A new PLC-based smart metering architecture for medium/low voltage grids: Feasibility and experimental characterization

Abstract This paper investigates the feasibility of a smart metering architecture for modern power grids in the smart cities framework. A particular focus is made on Automatic Meter Reading, with the aim of facing some costs and safety drawbacks of current solutions (such as dependence from wireless communication providers, reliability problems in bad weather conditions, and exposition to cyber-attacks). The proposed architecture exploits power line communications (PLC) at both low and medium voltage level, thanks to new devices and an innovative medium voltage PLC coupling system. The new coupling solution and the whole smart metering architecture are experimentally verified in a wide freq…

An Innovative Power Line Communication solution For Medium Voltage Smart Grids Applications

This paper summarizes the authors research activity concerning the design, modeling and experimental characterization of a new coupling system for medium voltage (MV) narrow band power line communications (NB-PLC). The proposed solution has been patented by authors and it exploits the capacitive divider of voltage detecting systems (VDSs) normally used to reveal the mains voltage presence, thus avoiding the use of dedicated MV couplers. In the following, the modeling of the VDS capacitive divider is presented and the interface card design is described, based on simulation of the whole PLC transmission channel. Laboratory tests are also presented. Finally, the results are shown of an on-fiel…

A Virtual Tool for Load Flow Analysis in a Micro-Grid

This paper proposes a virtual tool for load flow analysis in energy distribution systems of micro-grids. The solution is based on a low-cost measurement architecture, which entails low-voltage power measurements in each secondary substation and a voltage measurement at the beginning of the medium voltage (MV) feeder. The proposed virtual tool periodically queries these instruments to acquire the measurements. Then, it implements a backward&ndash

Incremental heuristic approach for meter placement in radial distribution systems

The evolution of modern power distribution systems into smart grids requires the development of dedicated state estimation (SE) algorithms for real-time identification of the overall system state variables. This paper proposes a strategy to evaluate the minimum number and best position of power injection meters in radial distribution systems for SE purposes. Measurement points are identified with the aim of reducing uncertainty in branch power flow estimations. An incremental heuristic meter placement (IHMP) approach is proposed to select the locations and total number of power measurements. The meter placement procedure was implemented for a backward/forward load flow algorithm proposed by…

Measurement Uncertainty of Harmonic Emission Indicators based on IEEE Std. 1459-2010

The study presented in this paper is aimed at analyzing the measurement uncertainty impact on the evaluation of some power ratio parameters for harmonic emissions assessment based on IEEE Std. 1459-2010 apparent power decomposition. In addition to power factors for line utilization and harmonic pollution levels evaluation defined in the Standard, the study covers also some new parameters, which have been introduced by the authors as IEEE Std. 1459-2010 power quantities ratios. The measurement of the aforesaid parameters is implemented on a PC-based wattmeter, in order to investigate the measurement uncertainty impact on the evaluation of the power ratios. The obtained results show that, in …

Design of a Time Dissemination System Using Chirp Modulation for Medium Voltage Smart Grid Applications

The monitoring and the management of smart grid require an advanced communication infrastructure. The time synchronization is among the most important services such an infrastructure should offer. Several solutions are available to disseminate the time information in a distributed system; for instance, most of the times a global positioning system (GPS) receiver is used to recover accurate time information. However, GPS receivers need a clear view of the sky. Other solutions, like the use of a network-based synchronization mechanism, require a dedicated communication infrastructure, which is not always feasible for economical reason. Thus, the use of the power grid itself to disseminate a t…

Oil filled MV/LV Power Transformer Behavior in Narrow Band Power Line Communication Systems

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…

New Measurement Procedure for Load Flow Evaluation in Medium Voltage Smart Grids

The aim of this paper is to present a new approach for the medium voltage (MV) distribution network load flow analysis, mainly based on power measurement at the low voltage (LV) level of MV/LV distribution substations. This allows to use measurement instruments, usually already installed in the secondary substations, thus achieving an equally reliable measurement system with a lower cost compared to measurements at the MV side. The new approach can be applied using a proper communication system to collect the nodal measurements and an iterative algorithm based on ladder iterative technique (LIT) to compute the load flow. The validity of this method is presented and discussed on the basis of…

Implementation of a PLC Field Analyzer on a G3 Modem Platform

Nowadays, power line communications (PLC) are a widely used technology in distribution grids, both for automatic meter reading and automation applications. PLC performances (in terms of capacity, coverage, robustness, and data transmission rate) can be significantly affected by electrical network topologies, connected loads and disturbances. Thus, utilities and modem manufacturers are increasing their interest in electrical network characterization. In this framework, a software tool is proposed in this paper to measure received signal and noise levels. As case study, it is implemented on a G3 PLC transceiver, widely used for smart metering purposes. In this way, a PLC channel characterizat…

Secondary substation power line communications for medium voltage smart grids

In this paper a performance analysis is carried out, in order to evaluate the possibility to employ power line communication (PLC) between secondary substations of a medium voltage (MV) distribution networks in a smart grid. The study is focused on the analysis of PLC technologies and the evaluation of the influence quantities on the communication performance in the most common case of by-pass connection at MV bus-bars of secondary substations. Different quantities have been analyzed as modulation techniques, requested bandwidth and bitrate, coupling device and system attenuation versus frequency in order to find the best solution for a reliable communication system. A complete model of a r…

Measurement and communication interfaces for distributed generation in smart grids

The aim of this work is to perform a feasibility study on the measurement and communication strategies for the development of a new generation of interface devices for distributed generators and their integration on smart grids. The communication system can use one or more technologies, at the various levels, creating a low cost network infrastructure, in the framework of a SCADA (Supervisory Control and Data Acquisition) architecture. As regards the measurements, the attention is focused on the anti-islanding protection, based on a hybrid solution, which makes use of local measurements and communications with the grid, at both MV and LV level by employing the PLC technology. Some simulatio…

Characterization of Current Transformers in the Presence of Harmonic Distortion

The CTs performance under distorted conditions are usually characterized by means of the frequency response test. In this paper a new way to characterize CTs, closer to real operative conditions, is proposed. The harmonic phase angle and ratio errors are measured when the CTs are excited with a nonsinusoidal current composed of a fundamental and one harmonic, with adjustable phase shift. The errors measured using the new approach were found larger than the ones obtained with the frequency response. This suggests that frequency response is not a reliable method to evaluate the CT performance under distorted conditions.

Campagna di misure sulla rete elettrica dell’isola di Favignana per la caratterizzazione di reti di accoppiamento per la trasmissione di segnali su cavi di media tensione

Un campione di potenza basato su schede di acquisizione commerciali. Prove sperimentali e valutazione dell'incertezza

Measurements methodology for the reliability evaluation of intelligent power modules

The paper describes a measurement methodology for the reliability evaluation of new intelligent power electronics modules (IPMs). In particular, the evaluation of the IPMs immunity to radio frequency conducted disturbances has been performed, at different operating thermal conditions, designing a suitable measurement set up in a shielded room. Moreover, the thermal performances of the devices have been analyzed, setting up a proper experimental test bench. The measurements procedures are detailed described. © 2014 IEEE.

Problematiche di misura della potenza attiva armonica