Power Line Communication Signal Research Articles

Noise mitigation method for power line communication based on cross-correlation analysis

Abstract Noise has a significant impact on the transmission rate and reliability of power line communication(PLC), which has become a crucial factor affecting PLC. In order to enhance the noise resistance of PLC, this paper proposes a noise mitigation method for PLC based on cross-correlation analysis. Firstly, the characteristics of OFDM signals based on PSK modulation are analyzed. Subsequently, reference signals are created for the purpose of cross-correlation with the PLC signal. Then, the phase of each subcarrier can be obtained. The PLC signal is reconstructed by utilizing the obtained phase, thereby achieving noise mitigation. Finally, the algorithmic program has been written for the simulation of the method in MATLAB. The simulation results show that the noise mitigation method can successfully remove the noise from PLC signals with signal-to-noise ratios within -20dB.

Power Line Communication and Sensing Using Time Series Forecasting.

Smart electrical grids rely on data communication to support their operation and on sensing for diagnostics and maintenance. Usually, the roles of communication and sensing equipment are different, i.e., communication equipment does not participate in sensing tasks and vice versa. Power line communication (PLC) offers a cost-effective solution for joint communication and sensing for smart grids. This is because the high-frequency PLC signals used for data communication also reveal detailed information regarding the health of the power lines that they travel through. Traditional PLC-based power line or cable diagnostic solutions are dependent on prior knowledge of the cable type, network topology, and/or characteristics of the anomalies. In this paper, we develop a power line sensing technique that can detect various types of cable anomalies without any prior domain knowledge. To this end, we design a solution that first uses time-series forecasting to predict the PLC channel state information at any given point in time based on its historical data. Under the approximation that the prediction error follows a Gaussian distribution, we then perform chi-squared statistical test to build an anomaly detector which identifies the occurrence of a cable fault. We demonstrate the effectiveness and universality of our sensing solution via evaluations conducted using both synthetic and real-world data extracted from low- and medium-voltage distribution networks.

Algorithms for Modulation Recognition of Narrowband Power Line Carrier Communication Signals

Automatic identification of modulated signals is an important technology of power line communication. Aiming at the problems of low signal recognition rate and characteristic parameter extraction in power line communication channel, this paper uses amplitude variance value of wavelet transform and higher order cumulant as the identification parameter, and designs a signal recognizer based on improved support vector machine. Under the condition of power line channel environment, the recognizer of this paper is less than the existing recognition method in the computational complexity, and has good robustness to power line noise. At the same time, it avoids the shortcomings of traditional neural network such as under-learning and over-learning. The simulation results show that when the SNR is 5 dB, power line communication signals through the recognizer, which the correct identification rate can reach 91%.

Construction and Experimental Verification of Novel Online Partial Discharge Monitoring System Using Power Line Communication

In this research, we aim to construct a completely new partial discharge (PD) monitoring system that applies inexpensive power line communication (PLC). We have proposed a PD detection method and monitoring system (PDMS-PLC) on the basis of PLC signal transfer rare is affected by an error due to disturbance. An attempt is made to identify PD source from the quadrant dependence of information transmission rate (hereinafter referred to PHY rate [Mbps]) by selecting a pair of quadrants of applied voltage phase; i.e. 1st and 3rd quadrants, or 2nd and 4th ones. It was found that the PHY (Abbreviation for the lowest physical layer in the OSI (open systems interconnection) hierarchical model.) rate number distribution reflects the PD characteristics obtained by the phase resolved PD (PRPD) pattern. Environmental noise level is also measured at an actual substation using PDMS-PLC. Consequently, the applicability of PDMS-PLC to PD signal detection and defect type identification is suggested.

Narrowband PLC Channel Attenuation Due to a Multi-Grounded Neutral

This paper presents a theoretical study on the influence of a multi-grounded neutral on the transmission of narrowband power-line communication (PLC) signals through a two-wire medium-voltage distribution line. Three different methods are proposed to calculate the transfer function of the line in the 3-500 kHz range: (i) nodal admittance method; (ii) travelling wave method; (iii) electrically-short line approach. The validity, advantages and shortcomings of each method are presented and discussed. It is shown that improving the grounding impedance at the transmitter and receiver locations will contribute to reducing the channel attenuation. It is also shown that the number of intermediate grounding points along the neutral is more relevant for the attenuation of PLC signals than their impedance. In general, increasing such number will always reduce the attenuation in frequencies where the line is electrically short. A similar behavior is observed at the higher end of the 3-500 kHz range provided the grounding interval is less than 300 m, which is half wavelength of the 500 kHz frequency. If the separation between grounding points is greater than that, reducing the number of grounding points is likely to reduce the average channel attenuation, but at the cost of introducing multiple resonant frequencies.

Effect of Non-Optimal Amplitude Frequency Response on Transmission of Power Line Communication Signals

Power line Communication (PLC) systems represent a relatively recent and rapidly evolving technology, aimed at the utilization of the electricity power lines for the transmission of data. This is due to increasing demand of low cost telecommunication, broadband and access to internet services. Power lines are inherently the most attractive medium for home networking due to its universal existence in homes, the abundance of alternating current outlets and the simplicity of the power plug. This work presented the effect of non-optimal amplitude frequency on transmission of power line communication signals by utilizing Orthogonal Frequency Division Multiplexing (OFDM) system. The simulation was carried out using MATLAB/SIMULINK with additive white Gaussian noise (AWGN) in order to obtain correct simulation performance results. Two channels of PLC were considered, the worse channel was taken into account and the channel output signal power was obtained. Bit Error Rate (BER) of Binary Phase Shift Keying (BPSK) in conjunction with multipath channel was used for a comparative performance of the studies. The results indicated that data transmission in PLC environment needed a signal to be amplified or transmitted at higher powers. The result also showed that non-optimal amplitude frequency response had no effect on transmission of the PLC signal in the frequency bands despite the low noise signal in the system. The result demonstrated that OFDM exhibited better BER performance for providing adequate transmission channel for information over a PLC system. This approach provided accurate reliability, security and robustness for better management of available energy resources to overcome the limitations of existing Power line communication technology. Keywords: Power Line Communication, Bit Error Rate, Orthogonal Frequency Division Multiplexing, Gaussian Noise, Transmission Line, Binary Phase Shift Keying DOI : 10.7176/JIEA/10-1-03 Publication date: January 31 st 2020

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 single carrier PSK modulated PLC signals with a center frequency from 50–200 kHz. In this paper, a new prototype is developed with a larger bandwidth, up to 164 kHz, thus allowing to couple multicarrier G3-PLC signals using orthogonal frequency division multiplexing (OFDM) digital modulation. This modulation ensures a more robust communication even in harsh power line channels. In the paper, the new coupling system design is described in detail. A new procedure is presented for tuning the coupling system parameters at first installation in a generic MV switchboard. Finally, laboratory and in-field experimental test results are reported and discussed. The coupling performances are evaluated measuring the throughput and success rate in the case of both 18 and 36 subcarriers, in one of the different tone masks standardized for the FCC-above CENELEC band (that is, from 154.6875–487.5 kHz). The experimental results show an efficient behavior of the proposed coupler allowing a two-way communication of G3-PLC OFDM signals on MV networks.

Experimental Analysis of Superconducting Line Trap Based on HTS Coil and HTS Electrode Capacitor

For the future applications of high-temperature superconducting (HTS) cables in the smart grid with power line communication (PLC), it would be unavoidable for HTS cables to experience the PLC signals. For the normal cables experiencing PLC signals, line trap is a commonly used inserted device to block signals from radiating across other cables. With HTS cables working at low temperature, superconducting line trap (SLT) based on HTS coil and HTS electrode capacitor might play a role to achieve a desired transmission path of PLC signals across HTS cables. Since there still remains a research gap of SLT, a prototype is proposed in this paper and its characteristics are presented by principle analysis as well as experimental research. It is found that SLT can offer a higher blocking impedance to carrier signals and produce much smaller loss at power frequency than the line trap made from normal materials.

Impulsive noise reduction techniques in power line communication: a survey

Power line communication (PLC) is a technology that permits data transmission using the electrical networks. In the last few years, research in the area of efficient wired home-networking services and smart grid has received a great interest thanks to the already-existing electrical networks and the ubiquitous sockets (outlets). However, the power line channel presents a challenging task and provides drastic medium for multimedia (audio, image and video) transmission. In fact, over the last decades, there has been an intense research in the area of impulsive noise reduction in PLC environments and numerous error-mitigation strategies have been proposed, thus the need for such a broad survey. To this end, this paper presents a comprehensive overview, with major emphasis on identifying strengthens and weaknesses of the state-of-the-art techniques, and discusses some challenges and future research directions thorough consolidation of related works on PLC signal protection strategies against impulsive noise effects.

Partial discharge detection using PLC receivers in MV cables: A theoretical framework

Partial discharge (PD) activity is a key indicator of the cable insulation health in medium-voltage networks. Many of these cables are used as transmission media, because power line communication (PLC) modems are installed at their ends.This paper proposes two techniques that allow broadband PLC receivers to detect PDs at the same time that the PLC signal is being demodulated. The proposed techniques are based on how PDs alter both, null, and zero-bit loaded carriers, commonly used in orthogonal frequency division multiplexing modems. Using the proposed techniques, a simple firmware modification is sufficient to add this new functionality to the already installed modems.This paper is mainly concerned with theoretical aspects of the proposed techniques, and no experimental validation has been done. Nevertheless, simulation results show that the proposed techniques can be used to detect different types of PDs. Four cases studies are analyzed: short- and long-distance PDs, and low- and high-energy PDs. Finally, the impact of the inter-carrier interference on the detection capability is studied, and some recommendations are made to mitigate its effects.

The Impact of Transformer Energization Levels on Powerline Communication Signal Integrity

There are advantages in implementing “through-transformer” powerline communication (PLC) on distribution grids. Research in distribution transformer characteristics has produced PLC strategies that take advantage of resonance phenomena due to shunt capacitive effects, which result in reduced high-frequency impedance at certain frequencies. However, the effects of phenomena associated with energized transformers on PLC signals has been largely overlooked. This paper outlines an experimental study of the PLC channel characteristics of two single-phase 11-kV/230-V transformers rated at 15 and 1 kVA, under various energization levels. Results show that distribution transformers can significantly influence the integrity of PLC signals impinging on their terminals by introducing noise, and signal amplitude and phase variation effects. This paper further identifies the phenomena behind these effects, and reveals how they can impact the quality of “through-transformer” PLC.

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 installing a dedicated MV coupler, thus avoiding the related costs of the coupler, the installation, and the temporary service interruption. The innovative device is able to couple digitally modulated narrowband PLC signals with modulation rate up to 19.2 kbit/s. In this paper, first a description of the proposed solution is reported. Second, its communication performance has been tested in laboratory. Finally, different tests have been carried out in two MV smart grid real installations under normal operation, i.e., in the presence of the mains voltage.

Fractal and multi-fractal features of the broadband power line communication signals

Broadband power line communications (PLC) is considered to be one of the most promising technologies to fulfill data transmission in smart grids. To understand PLC signal characteristics and overcome the shortcomings of traditional statistical properties, the mono-fractal and multi-fractal theories are introduced to understand the self-similarity characteristics of the PLC signals. Four common methods, namely, rescaled range analysis, variance-time plot method, periodic diagram analysis and wavelet-based method are used to study the nonlinear properties. Fractal analysis at different frequencies and times are also performed to verify further. The results reveal self-similarity of the PLC signals. Besides the mono-fractal properties, the paper tests the multi-fractal properties of PLC signals by the means of multi-fractal detrended fluctuation analysis (MFDFA). We estimated the multi-fractal spectrum of power low exponents from the measured PLC signals. We also proposed a new algorithm to improve the traditional MFDFA, where wavelet theory is integrated.

Influence of the MV/LV Transformer Impedance on the Propagation of the PLC Signal in the Power Grid

Improving the operation of power grid and offering new smart applications, the deployment of a supervisory infrastructure is necessary. One solution to transmit data may be based on the power-line communication (PLC) technology. It consists of the superposition of high-frequency signals with the electrical signal of 50/60 Hz. However, the power grids have not been designed to operate in high frequencies. Therefore, they provide a transmission channel with difficult propagation conditions. This paper deals with the modeling of the medium-voltage/low-voltage (MV/LV) power transformers in PLC frequencies. The proposed models are based on the “lumped model” and “black box model.” They are performed in the frequency band from 1 kHz to 1 MHz on SPICE and MATLAB software, respectively. These models are based on impedance measurements and validated by experimental data. The advantages and drawbacks of each model are detailed from the presentation of the modeling method and simulation results. The comparison of the simulation results show that “black box model” offers good accuracy. The transmission results show that transformers are an important element in PLC studies because they provide significant losses. Moreover, these losses depend mainly on the values of the impedance terminals of the MV/LV transformer.

Propagation Characteristics of kHz Band PLC Signal on MV–LV Distribution System

SUMMARYThe kHz band power line communication (PLC) is one of the convincing mediums of the communication system for smart meter reading. Data transmission between medium‐voltage (MV) and low‐voltage (LV) points to pass the transformer by PLC is interested. In this paper, the PLC signal propagation characteristics between points of MV at substation and LV at customer are calculated and analyzed. The results show that direct communication between points on MV distribution line and most LV customers is impossible due to large propagation losses at MV–LV transformer and on LV distribution line.

On Improving Communication Robustness in PLC Systems for More Reliable Smart Grid Applications

Power-line communication (PLC) has been the main enabler for modernizing the aging electrical power grid. As such, PLC systems have been the subject of intensive research in the community. One of the major aspects of PLC is the link interface, for which orthogonal frequency-division multiplexing (OFDM) has been widely adopted. In this paper, we propose the application of orthogonal poly-phase-based multicarrier code division multiple access (OPP-MC-CDMA) due to its inherent better flexibility and signal-envelope properties which can be utilized to further enhance the reliability of PLC signals. The proposed OPP-MC-CDMA system is implemented with a minimum mean square error equalizer and nonlinear preprocessing to overcome the effects of bursty noise and multipath frequency-selective fading commonly experienced in PLC channels. We study the performance of this system in terms of the output signal-to-noise ratio (SNR) and symbol error rate with various constellation sizes of OPP codes under different noise scenarios and nonlinear processor’s thresholds. For comparison-sake, the performance of the OFDM scheme is included. The results reveal that the proposed approach always provides superior performance over the OFDM one with a maximum output SNR gain of up to 5.25 dB. It is also shown that the performance of the OPP-MC-CDMA technique improves when increasing the constellation size of the OPP codes, which consequently enhances the reliability of PLC.

A New Noise Mitigation Scheme in Power Line Communication Systems Based on the Principal Components Analyses

Power Line Communication (PLC) systems suffer from too severe noise contamination in the channels. In the paper, a new scheme was proposed based on the principal components analyses (PCA) to mitigate noises in PLC channels. The scheme consists of four steps. In the first step, the PLC signal with one dimension is generalized to a data set with multiple dimensions (degrees). In order to de‐correlate the new data set, generalized signals are whitened with Gaussian noises in the second step. For the uncorrelated data set, the PCA technology is applied to cancel noises in the transformed domain. As the last step, the PLC signals of interesting are recovered by applying the inverse transform matrix. The results from the simulated seismic signals and the measurements data verify the validity of the proposed scheme.

Influence of the channel instability on the PLC QoS

Intensive rollout of smart grids (SG) creates a special demand on communication networks. Especially, they have to supply sufficient quality of service (QoS) to a big number of customers. Therefore the required QoS becomes more demanding (e.g., minimum throughput have to be increased) and in meantime the cost of the network installation and management should be reduced. Power line communication (PLC) becomes a challenging technology inside SGs. It uses already available power cables and therefore reduces the installation costs of the network. In particular, the usage of PLC is beneficial for power utilities, which appear to be the owners of this communication medium. Nevertheless, PLC remains an emerging technology. Achievable QoS for particular PLC network scenarios are hard to predict and still need to be studied. It is reasoned by the fact, that the PLC environment (cable structure, electrical devices, etc.) induces special effects on the informational signal propagation over the communication medium. These effects may result in considerable impairments of the PLC signal. Nevertheless, with a usage of a cognitive mechanism a big part of them can be avoided or even taken as an advantage. This paper overviews the influence of the channel instability on the PLC QoS. A data link layer (DLL) of a PLC protocol can implement a channel prediction mechanism, which is beneficial for multiple PLC applications. A short description on this mechanism is also introduced in this paper.

The influence of soil electrical parameters on the electric field due to power line communications: Measurements of frequency-dependent soil parameters

The contribution of the present work is to demonstrate the influence of soil electrical parameters (conductivity and permittivity) on the electric field generated by power line communications (PLC). Soil samples were collected from beneath the high-voltage transmission lines under investigation and analyzed in the laboratory using a simplified method of measuring scattering parameters. These were converted into ABCD parameters in order to obtain the characteristic impedance and then the complex permittivity as a function of frequency. The employed methodology to find the soil electrical parameters as a function of the frequency was compared to the Smith and Longmire model, which is appropriate for modeling in the frequency range of PLC signals. The results obtained by both models for calculating the electrical parameters were applied to the electric field equations developed by D’Amore. Although high-voltage transmission lines generally use narrowband PLC for control system operations, the present work implemented both narrow and broadband analyses.

Frequency domain based LS channel estimation in OFDM based Power line communications

This paper is focused on low voltage power line communication (PLC) realization with an emphasis on channel estimation techniques. The Orthogonal Frequency Division Multiplexing (OFDM) scheme is preferred technology in PLC systems because of its effective combat with frequency selective fading properties of PLC channel. As the channel estimation is one of the crucial problems in OFDM based PLC system because of a problematic area of PLC signal attenuation and interference, the improved LS estimation technique is proposed. We investigate and evaluate proposed frequency domain LS channel estimation method for OFDM based power line communication system. Also performance comparing with existing pilot based estimation algorithms towards proposed method in terms of their computational complexity, error correction, and suitability conditions is made.