Field Trials for the Empirical Characterization of the Low Voltage Grid Access Impedance From 35 kHz to 500 kHz

The access impedance of low-voltage (LV) power networks is a major factor related to the performance of the narrow-band power line communications (NB-PLCs) and, in a wider sense, to electromagnetic compatibility (EMC) performance. Up to date, there is still a lack of knowledge about the frequency-dependent access impedance for frequencies above 9 kHz and up to 500 kHz, which is the band where the NB-PLC operates. The access impedance affects the transmission of the NB-PLC signal, and it determines the propagation of the non-intentional emissions that may disturb other electrical devices, including malfunctioning or reduced lifetime of equipment. This paper presents the results of field measurements of the LV access impedance up to 500 kHz in different scenarios, with measurement locations close to end users and near transformers. The results provide useful information to analyze the characteristics of the LV access impedance, including variation with frequency, ranges of values for different frequency bands, and analysis of specific phenomena. Moreover, the results reveal a diverse frequency-dependent behavior of the access impedance in different scenarios, depending on the grid topology, the number of end users (that is, number and type of connected loads), and the type of transformation center. Overall, the results of this paper offer a better understanding of the transmission of NB-PLC signals and EMC-related phenomena.The authors would like to thank Iberdrola for the availability and the collaboration of authorized staff for carrying out the field trials

European White Book on Real-Time Power Hardware in the Loop Testing : DERlab Report No. R- 005.0

The European White Book on Real-Time-Powerhardware-in-the-Loop testing is intended to serve as a reference document on the future of testing of electrical power equipment, with specifi c focus on the emerging hardware-in-the-loop activities and application thereof within testing facilities and procedures. It will provide an outlook of how this powerful tool can be utilised to support the development, testing and validation of specifi cally DER equipment. It aims to report on international experience gained thus far and provides case studies on developments and specifi c technical issues, such as the hardware/software interface. This white book compliments the already existing series of DERlab European white books, covering topics such as grid-inverters and grid-connected storag

pandapower - an Open Source Python Tool for Convenient Modeling, Analysis and Optimization of Electric Power Systems

pandapower is a Python based, BSD-licensed power system analysis tool aimed at automation of static and quasi-static analysis and optimization of balanced power systems. It provides power flow, optimal power flow, state estimation, topological graph searches and short circuit calculations according to IEC 60909. pandapower includes a Newton-Raphson power flow solver formerly based on PYPOWER, which has been accelerated with just-in-time compilation. Additional enhancements to the solver include the capability to model constant current loads, grids with multiple reference nodes and a connectivity check. The pandapower network model is based on electric elements, such as lines, two and three-winding transformers or ideal switches. All elements can be defined with nameplate parameters and are internally processed with equivalent circuit models, which have been validated against industry standard software tools. The tabular data structure used to define networks is based on the Python library pandas, which allows comfortable handling of input and output parameters. The implementation in Python makes pandapower easy to use and allows comfortable extension with third-party libraries. pandapower has been successfully applied in several grid studies as well as for educational purposes. A comprehensive, publicly available case-study demonstrates a possible application of pandapower in an automated time series calculation

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 applications, such as smart meters. To this aim, an innovative measurement tool is proposed, which does not need a specific characterization signal to be injected because it uses the preamble of a generic PLC transmission. Moreover, the impedance calculation is performed using an FFT analysis, which does not require high computational capabilities. These features allowed the proposed tool to be implemented using a G3-PLC transceiver, embedded in many commercial smart meters, and low-cost additional hardware. This article shows how the proposed system correctly measures the PLC impedance on CENELEC A, B, and FCC frequency ranges

Development of impedance spectroscopy based in-situ, self-calibrating, on-board wireless sensor with inbuilt metamaterial inspired small antenna for constituent detection in multi-phase mixtures like soil

Real time and accurate measurement of sub-surface soil moisture and nutrients is critical for agricultural and environmental studies. This work presents a novel on-board solution for a robust, accurate and self-calibrating soil moisture and nutrient sensor with inbuilt wireless transmission and reception capability that makes it ideally suited to act as a node in a network spread over a large area. The sensor works on the principle of soil impedance measurement by comparing the amplitude and phase of signals incident on and reflected from the soil in proximity of the sensor. The permittivity of the soil dielectric mixture which is calculated from these impedance measurements is used as input parameter to the dielectric mixing models which are used to estimate the ionic concentration in soil. The inbuilt wireless transceiver system is connected to a specially designed metamaterial inspired small antenna in order to reduce the sensor size while keeping the path losses to a minimum by using a low frequency. This composite right-left handed (CRLH) antenna for wireless transmission at 433 MHz doubles up as an underground, sensing element (external capacitor) and integrates with the on-board sensor for soil moisture and nutrient determination. The input impedance of the CRLH sensor, surrounded by the soil containing moisture and nutrient and other ions, is measured at multiple frequencies. It is shown that the change in moisture and ioinic-concentration can be successfully detected using the sensor. The inbuilt self-calibrating mechanism makes the sensor reliable at different environmental conditions and also useful for remote, underground and hand-held applications. A multi-power mode transceiver system has been designed to support the implementation of an energy efficient medium-access-control

Time-domain multitone impedance measurement system for space applications

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a time-domain methodology to measure the devices' live impedance at the frequency range between 30 Hz and 100 kHz. This measurement is a requirement for some space applications to ensure the stability between DC/DC converters and the onboard power. The methodology is based on a multitone excitation combined with current and voltage measurements performed with an oscilloscope. The experiments show that the measurement system obtains accurate results and offers new capabilities to deal with the drawbacks that traditional frequency-sweep instrumentation implies. The multitone approach injects signals at the entire frequency range simultaneously. Therefore, the measurement system is able to characterize time-varying and the nonlinear devices. The time-domain measurement system has been validated through different test cases achieving excellent results compared with the ones obtained using the reference impedance frequency-sweep approach.The project on which these results are based has received funding from the European Union's Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No. 801342 (TecniospringINDUSTRY) and the Government of Catalonia's Agency for Business Competitiveness (ACCIÓ). This work was supported by the Spanish “Agencia Estatal de Investigación” under project PID2019-106120RBC31/AEI/10.13039/501100011033.Peer ReviewedPostprint (author's final draft

Real-time power system impedance estimation for DG applications: Using PV-inverter based harmonic injection method

On-line power system (PS) Thévenin equivalent impedance (TEI) estimation involves the reduction of the PS's complex circuit into a simple form that provides valuable insight into its state and behaviour. It finds application in numerous areas such as voltage stability monitoring and islanding detection. In the context of distributed generation (DG), on-line TEI estimation can be easily implemented in existing hardware to add functionality and improve the operation of power converters – the key components of DG systems. Two distinct methods of on-line PS TEI estimation exist. The passive method involves only measurement of voltage and current, whereas the active method involves injection of current into the PS and measurement of the response. This work is focused on the active method. Through a review of the available literature, limitations of past work are highlighted. It is shown that the nature of current injection varies greatly in different works and that evaluation of implementation performance is generally not thorough. Little consideration has been made of the effect of injection current level and frequency on the performance of on-line TEI estimation. Furthermore, the behaviour of the grid and its impact has not been thoroughly investigated. In this work, the active method is implemented in a three-phase PV-inverter and thoroughly tested in terms of its TEI estimation accuracy. Dependence of said accuracy on parameters such as the level of injected current and its frequency is shown to be high through tests performed on the live PS at two locations. These parameters are optimised such that TEI accuracy is maximised and the performance of the device is shown to be good compared to calibration equipment. The accuracy of PS TEI tracking is evaluated and quantified. Considerations are also made of the device's hardware limitations and their effect. A process by which a device's TEI estimation accuracy can be thoroughly evaluated is developed through this work. The behaviour of the PS's TEI is also investigated over long periods and characterised. It is found that the TEI remains steady around an average level in both test locations, with a low standard deviation. Consistency in results is found to be high between the two tests

A new SOLT calibration method for leaky on-wafer measurements using a 10-term error model

We present a new Short-Open-Load-Thru (SOLT) calibration method for on-wafer S-parameter measurements. The new calibration method is based on a 10-term error model which is a simplified version of the 16-term error model. Compared with the latter, the former ignores all signal leakages except the ones between the probes. Experimental results show that this is valid for modern vector network analyzers (VNA). The advantage of using this 10-term error model is that the exact values of all error terms can be obtained by using the same calibration standards as the conventional SOLT method. This avoids not only the singularity problem with approximate methods, such as least squares, but also the usage of additional calibration standards. In this paper, we first demonstrate how the 10-term error model is developed and then the experimental verification of the theory is given. Finally, a practical application of the error model using a 10 dB attenuator from 140 GHz to 220 GHz is presented. Compared with the conventional SOLT calibration method without crosstalk corrections, the new method shows approximately 1 dB improvement in the transmission coefficients of the attenuator at 220 GHz

Estimation and detection of transmission line characteristics in the copper access network

The copper access-network operators face the challenge of developing and maintaining cost-effective digital subscriber line (DSL) services that are competitive to other broadband access technologies. The way forward is dictated by the demand of ever increasing data rates on the twisted-pair copper lines. To meet this demand, a relocation of the DSL transceivers in cabinets closer to the customers are often necessary combined with a joint expansion of the accompanying optical-fiber backhaul network. The equipment of the next generation copper network are therefore becoming more scattered and geographically distributed, which increases the requirements of automated line qualification with fault detection and localization. This scenario is addressed in the first five papers of this dissertation where the focus is on estimation and detection of transmission line characteristics in the copper access network. The developed methods apply model-based optimization with an emphasis on using low-order modeling and a priori information of the given problem. More specifically, in Paper I a low-order and causal cable model is derived based on the Hilbert transform. This model is successfully applied in three contributions of this dissertation. In Paper II, a class of low-complexity unbiased estimators for the frequency-dependent characteristic impedance is presented that uses one-port measurements only. The so obtained characteristic impedance paves the way for enhanced time domain reflectometry (a.k.a. TDR) on twisted-pair lines. In Paper III, the problem of estimating a nonhomogeneous and dispersive transmission line is investigated and a space-frequency optimization approach is developed for the DSL application. The accompanying analysis shows which parameters are of interest to estimate and further suggests the introduction of the concept capacitive length that overcomes the necessity of a priori knowledge of the physical line length. In Paper IV, two methods are developed for detection and localization of load coils present in so-called loaded lines. In Paper V, line topology identification is addressed with varying degree of a priori information. In doing so, a model-based optimization approach is employed that utilizes multi-objective evolutionary computation based on one/two-port measurements. A complement to transceiver relocation that potentially enhances the total data throughput in the copper access network is dynamic spectrum management (DSM). This promising multi-user transmission technique aims at maximizing the transmission rates, and/or minimizing the power consumption, by mitigating or cancelling the dominating crosstalk interference between twisted-pair lines in the same cable binder. Hence the spectral utilization is improved by optimizing the transmit signals in order to minimize the crosstalk interference. However, such techniques rely on accurate information of the (usually) unknown crosstalk channels. This issue is the main focus of Paper VI and VII of this dissertation in which Paper VI deals with estimation of the crosstalk channels between twisted-pair lines. More specifically, an unbiased estimator for the square-magnitude of the crosstalk channels is derived from which a practical procedure is developed that can be implemented with standardized DSL modems already installed in the copper access network. In Paper VII the impact such a non-ideal estimator has on the performance of DSM is analyzed and simulated. Finally, in Paper VIII a novel echo cancellation algorithm for DMT-based DSL modems is presented