Power Line Communication Channel Research Articles

A Frequency Control Strategy Using Power Line Communication in a Smart Microgrid

This paper presents an application of power-line communication (PLC) as a viable solution for frequency regulation in a smart microgrid. The microgrid under consideration comprises a diesel generator with a frequency controller and another synchronous generator operating in the constant power mode. Frequency regulation is achieved in the microgrid by communicating the frequency deviation (information) from the control center to the diesel generator using PLC. The information received at the other end is used for frequency regulation. A simple yet effective M -ary amplitude-shift keying (ASK) modulation-based PLC system is proposed for information transmission. A comparative analysis of M -ary ASK and M -ary frequency-shift keying (FSK)-based PLC systems is also presented. Approximate closed-form expressions for the average symbol error rate and the average achievable rate are derived for both the PLC systems, assuming that the PLC channel coefficients and the additive impulsive noise samples are derived from a log-normal distribution and a Bernoulli-Gaussian process, respectively. The results show that M -ary ASK is a better choice for PLC than M -ary FSK. Furthermore, the delay introduced in the control loop while using the proposed PLC system is negligible, and therefore, the stability of the microgrid is also ensured.

Statistical Characterization of Indian Residential Networks for Powerline Communication

Despite different powerline channel modeling techniques, developed so far, there are still specific dynamic, varying parameters (viz. the random load variation and inconsistent electrical wiring) to be studied for a valid and reliable power line communication (PLC) model. Statistical characterization of PLC channel may provide the required background for refinement of these existent models. In this paper, the Indian residential networks are statistically analyzed in the frequency range of 1-100 MHz. This also includes the comprehensive analysis of line impedance, stationary noise, channel capacity and average channel gain. From the measurements, the noise spectrum density is found to be less than -90 dBm at a frequency less than 1 MHz and is almost constant after 70 MHz. The minimum and maximum channel capacity of the network is 71.5 Mbps and 97.7 Mbps respectively. The Average channel gain is estimated at -30 dB. The paper also reviews the channel transfer function developed by top-down and bottom-top approaches. Finally, some additional factors influencing the PLC channel are also discussed.

Performance Analysis of an Opportunistic Relaying Power Line Communication Systems

Powerline communication (PLC) is an attractive approach to providing information transfer services for future smart grids. However, due to high attenuation and interference, it is a great challenge to achieve reliable transmissions over PLC channels. In this letter, we propose an opportunistic decode-and-forward-based multiple-relaying (ODFR) scheme to enhance the performance of PLC networks, where the optimal relay is selected dynamically for data forwarding. Specifically, we first formulate the cumulative distribution functions (CDFs) of the received signal-to-noise ratio by exploiting statistical properties of the PLC channels. Then, drawing upon this derived CDF, we further develop the closed-form expressions of outage probability and approximate capacity for the proposed ODFR scheme. Simulations validate the consistency of our analytical results with Monte Carlo simulations.

A PLC Channel Model for Home Area Networks

Smart meters (SMs) are key components of the smart grid (SG) which gather electricity usage data from residences and businesses. Home area networks (HANs) are used to support two-way communications between SMs and devices within a building such as appliances. This can be implemented using power line communications (PLCs) via home wiring topologies. In this paper, a bottom-up approach is designed and a HAN-PLC channel model is obtained for a split-phase power system which includes branch circuits, an electric panel with circuit breakers and bars, a secondary transformer and the wiring of neighboring residences. A cell division (CD) method is proposed to construct the channel model. Furthermore, arc fault circuit interrupter (AFCI) and ground fault circuit interrupter (GFCI) circuit breaker models are developed. Several HAN-PLC channels are presented and compared with those obtained using existing models.

The Influence of the Branch Loads on Low-Voltage Power Line Communication Channel

The Influence of the Branch Loads on Low-Voltage Power Line Communication Channel

Channel Estimation Based on Compressed Sensing Technique for Low-Voltage Power Line Communication

Broadband low-voltage power line communication (PLC) has many advantages including less investment cost, construction speed, and convenient access. Since the orthogonal frequency division multiplexing (OFDM) technology has strong anti-jamming and anti-frequency selective fading characteristics naturally it becomes a better low voltage power line communication solution. We proposed an OFDM channel estimation method based on compressed sensing (CS) technique according to the channel characteristics of low-voltage power lines. CS algorithm in OFDM system was discussed and an orthogonal matching pursuit (OMP) algorithm was applied to reconstruct the PLC channel information. The simulation results showed that the communication channel estimation method based on CS technique was feasible in PLC system, and the validity of information transmission in OFDM systems can be enhanced.

Accurate Low Access Impedance Measurements With Separated Load Impedance Measurements on the Power-Line Network

The precise knowledge of the access impedance and load impedances on the power-line communication (PLC) medium enables the optimum design of smart grid applications. The impedance of the PLC channel is strongly affected by the unmatched loads and considered as time- and frequency-dependent. This problem is the main reason for reducing the power amplifier output level of PLC modems, the transmitted signals, and the data rate of the PLC channel. This paper presents a description of an accurate access impedance measurement system in the frequency range 30–500 kHz with calibration processes and procedure to measure loads impedances on the power grid. This system provides a cancellation of the main frequency component and enables the analysis of the cyclostationary behavior of the access impedance of the power line. Off-line and online impedance measurements on different power outlets are presented. Very low and time-variant access impedances are found. This impedance behavior on the power line is related to the power supply unit and the electromagnetic interference filter design. The presented impedance measurements are evaluated and can be used to classify loads behavior.

Desarrollo Y Simulación De Un Modelo De Transceptor Basado En Prime Para Simulación Sobre Canal PLC

The choice of modification technique for a communications system depends to a large extent on the nature and characteristics of the medium in which it must operate (Hrasnica et al., 2005). In a PLC (Power Line Communications) system, the first applications in the LDR band (oriented to the control of devices) operated with monocarrier modulations, such as ASK, BPSK, and FSK. This allows for low implementation costs, provided that it operates at low data rates and with an error correction system. It is clear that applications require a higher data rate. The modulation technique must overcome challenges such as the necessary equalization for the cause of the non-linearity of the channel, or avoid the propagation delays and the multipath caused by the impedance differences in the branches. Likewise, it must offer flexibility and avoid the use of certain frequencies if they are altered or assigned to another service and, therefore, cannot be used in PLC. In this scenario, one of the techniques that have been imposed in the most used developments in NB-PLC as in BB-PLC has been Orthogonal Frequency Division Multiplexing (OFDM). One of its most attractive aspects from the point of view of its complexity is the possibility of implementing the structure of its multifrequency modulation and demodulation scheme through a simple Inverse Discrete Fourier Transform (IDFT) and its corresponding direct transform, Fast Fourier Transform (FFT). Based on this technique, an appropriate transceiver scheme for operating on a PLC channel model was presented. This development implements the error correction technique proposed for NB-PLC.

Modeling simulation and performance evaluation of low voltage power line communication channel

Modeling simulation and performance evaluation of low voltage power line communication channel

Bottom-up single-wire power line communication channel modeling considering dispersive soil characteristics

This paper investigates the influence of frequency-dependent soil conductivity and permittivity on narrowband and broadband power line communication (PLC) channel modeling using transmission line theory. For narrowband PLC channels, the variation of the transfer function H(f) of a single overhead wire over a finitely conducting ground due to frequency-dependent soil parameters is minimal for low-resistivity soils, but more relevant for high-resistivity soils in the upper frequency range. For broadband PLC channels, H(f) strongly depends on the soil model for frequencies below 10MHz or so, but is relatively insensitive to this parameter at higher frequencies. The average channel attenuation is more affected by soil model and soil parameters than the achievable data rate. Also, the voltage definition assumed in the derivation of the per-unit-length parameters of the line has little influence on the results. A comparison between different formulations traditionally used in PLC channel modeling indicates that the admittance associated with a finitely conducting ground should not be neglected in the modeling of broadband PLC channels.

Masreliez-Equalized VOFDM in Non-Gaussian Channels: Power Line Communication Systems

In this paper, we derive a nonlinear equalizer for a fading channel with non-Gaussian noise. In particular, we look into the effects of non-Gaussian noise over power line channels that severely affect communication signals. Unlike most existing work based on orthogonal frequency-division multiplexing (OFDM) in the literature, we investigate the performance of vector OFDM (VOFDM) over multipath power line communication (PLC) channels contaminated with Middleton Class-A noise. To reduce the impact of impulsive noise, we propose a novel filter to equalize the output of the channel. The performance of the equalizer is evaluated in terms of bit error rate (BER), and the impact of several impulsive noise parameters are examined at the receiver. Results show that the proposed system can considerably improve the BER performance in comparison to the conventional OFDM scheme. In addition, it is shown that increasing the number of vector blocks of the VOFDM system will enhance the BER performance under the same condition. The proposed nonlinear equalizer improves the performance of VOFDM system successfully at low signal-to-noise ratios (SNRs), at some instances it nearly halved the probability of error with respect to linear filter.

Vector OFDM Transmission Over Non-Gaussian Power Line Communication Channels

Most of the recent power line communication (PLC) systems and standards, both narrow-band and broadband, are based on orthogonal frequency-division multiplexing (OFDM). This multiplexing scheme however suffers from the high peak-to-average power ratio (PAPR) which can considerably impact the energy efficiency, size and cost of PLC modems as well as cause electromagnetic compatibility (EMC) issues. This paper investigates the performance of vector OFDM (VOFDM), which has inherently better PAPR properties, over non-Gaussian broadband PLC channels equipped with two nonlinear preprocessors at the receiver. In addition, the low PAPR property of the VOFDM system is exploited to further enhance the efficiency of the nonlinear preprocessors. The achievable gains are studied in terms of the complementary cumulative distribution function of the PAPR, probability of noise detection error and the signal-to-noise ratio at the output of the nonlinear preprocessors. For comparison's sake, the performance of conventional OFDM systems is also presented throughout the paper. Results reveal that the proposed system is able to provide up to 2 dB saving in the transmit power relative to the conventional OFDM under same system conditions, which eventually also translates into a system that is more resilient to EMC limits, reduced cost and size of PLC modems. It is also shown that the achievable gains become more significant as the vector block (VB) size of the VOFDM system is increased.

Narrowband Modeling of Single-Wire Earth Return Distribution Lines

The implementation of powerline communication (PLC) on single-wire earth return (SWER) grids requires high-frequency earth path characterization. The empirical determination of these characteristics is not practical for large grids. Analytical expressions may be used to estimate the high-frequency characteristics of earth paths; however, this paper shows that this approach can lead to errors when modeling line-to-earth path PLC channels. Therefore, a hybrid empirical/analytical earth path characterization method, based on heuristic correlations of measurement results with a lossy capacitor model, is hereby proposed. Further measurements on an experimental SWER line using two types of conductors were carried out. The results indicate that narrowband PLC implementation on SWER grids is feasible, and that conductors with similar size and material composition may have similar high-frequency characteristics, regardless of the construction method used. The proposed earth path characterization method was verified by comparing measurements with simulations of frequency-dependent analytical and constant parameter hybrid, per-unit SWER transmission line models.

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.

Approach for modelling of broadband low‐voltage PLC channels using graph theory

Broadband power line is an important way of communication in low-voltage distribution networks because a power line is everywhere nowadays. However, due to the heterogeneity of a practical power-line network and various loads connected to its termination points, modelling and simulation of power-line communication (PLC) channels are difficult and complicated issues. In this work, the authors propose a novel PLC channel modelling approach using graph theory for the first time when knowing the power-line network topologies and cable distributed parameters. The approach utilises simple and effective recursive operations in solving the k -shortest paths to estimate the channel transfer function for a specific power-line network, it overcomes the complicated analytical derivation in computing the channel transfer function by the traditional two-port network in the bottom-up model and avoids to measure the actual channel in a top-down model. Their proposed approach is validated by transmission-line (TL) theory as well as measurement results, and it is also compared with TL theory. The results show that their proposed PLC channel modelling approach herein is simple to be implemented, it is expected to have extensive applications in broadband PLC systems for performance evaluations.

Performance Analysis of CDMA/ALOHA Networks in Memory Impulse Channels

Previous CDMA/ALOHA network performance analysis papers do not consider memory impulse channels. The Markov-Gaussian model can characterize the bursty nature of the memory impulsive noise in some wireless channels and power line communication (PLC) channels. In this paper, we propose the use of the Markov-Gaussian model in the throughput analysis of CDMA/ALOHA networks. The state transition diagram for the throughput analysis has one extra dimension to represent if the impulse noise is present or not. We derive the exact throughput analysis in memory impulse channels with and without channel load sensing protocol (CLSP). The analytic results demonstrate that if the level of the impulsive noise is higher, performance degradation is more and vice versa. Based on the analytic results, we also find the optimal CLSP threshold alpha for various impulse noise conditions. The analytic results of the throughput performance are all matched by the simulation results.

Energy-Per-Bit Performance Analysis of Relay-Assisted Power Line Communication Systems

This paper provides a comprehensive analysis of the energy efficiency performance for different relaying schemes over the non-Gaussian power line communication (PLC) channel. Specifically, amplify-and-forward (AF), decode-and-forward (DF), selective DF (SDF) and incremental DF (IDF) relaying systems are investigated. For a more realistic scenario, the power consumption profile of the PLC modems is assumed to consist of both dynamic and static power. For each system, we derive accurate analytical expressions for the outage probability and the minimum energy-per-bit performance. For the sake of comparison and completeness as well as to quantify the achievable gains, we also analyze the performance of a single-hop PLC system. Monte Carlo simulations are provided throughout this paper to validate the theoretical analysis. Results reveal that AF relaying over the non-Gaussian PLC channel does not always enhance the performance and that the IDF PLC system offers the best performance compared to all other schemes considered. It is also shown that increasing the channel variance, which is related to the PLC network branching, and impulsive noise probability can considerably deteriorate the system performance. Furthermore, when the end-to-end distance is relatively small, it is found that the single-hop PLC approach can perform better than AF relaying.

For More Energy-Efficient Dual-Hop DF Relaying Power-Line Communication Systems

Energy efficiency in multihop cooperative power-line communication (PLC) systems has recently received considerable attention in the literature. In order to make such systems more energy efficient, this paper proposes a relaying technique equipped with energy-harvesting capabilities. More specifically, we consider a dual-hop decode-and-forward (DF) broadband PLC relaying system in which the relay exploits the high noise inherent in PLC channels to further enhance energy efficiency; this system will be referred to as DF with energy harvesting (DF-EH). This study deploys, particularly, the time-switching relaying protocol for energy harvesting. An accurate analytical expression for the energy efficiency and a closed-form expression for the average outage probability of the proposed system are derived and then verified with Monte Carlo simulations. For the sake of comparison and to highlight the achievable gains, we also analyze the energy-efficiency performances and the average outage probabilities of the conventional DF relaying system, i.e., without energy harvesting, as well as that of the direct-link approach. Furthermore, various frequency selection and power allocation strategies, namely, optimal frequency selection, random frequency selection, and equal power allocation, exploiting the multiple power cables, are studied. Then, the impact of several system parameters such as the energy-harvesting time factor, various idle power consumption profiles, relay location, power allocation as well as different noise scenarios are examined. The results reveal that the proposed DF-EH system is able to provide energy efficiency improvements of more than 30% compared to the conventional DF relaying scheme. It is also shown that the proposed system with optimal frequency selection performs better at low SNR, whereas at high SNR the equal power allocation based system will have the best performance.

Channel model proposal for indoor relay‐assisted power line communications

Due to its tree-like topology, the point-to-point (P2P) indoor power line communication (PLC) channel exhibits a similar broadcasting property as the wireless propagation channel shows. However, after relay nodes are introduced, the relay-assisted PLC (RaPLC) channel shows some notable differences compared with its wireless counterpart. A lot of results about the relay-assisted wireless channel can be found in the literature, but the work of modelling RaPLC channel has rarely been discussed in detail. As the first attempt to fill this gap, we apply the ABCD method to compute the channel transfer function (CTF) of the RaPLC channel. It has been clarified that, in general, the CTF of RaPLC channel cannot be obtained as a cascade of two independent P2P PLC sub-channels located on two sides of the relay node. Also, it is shown that the challenge of generating CTF of the RaPLC channel can be transformed into a group of equivalent P2P PLC channel modelling tasks. Under the time-division duplexing constraint, the relay node changes its working mode from the receiving phase to the transmitting phase, which shows that the RaPLC channel is abruptly time-varying in nature. Following the hybrid bottom-up approach, a statistical channel model with a simple six-segment indoor power grid topology has been developed for simulation. Practical measurements and numerical examples verify our results.

First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

The realization of a Semi-Hidden Fritchman Markov models (SHFMMs) for power line communication (PLC) channel is only practicable if combined with efficient algorithms for learning and inference. This article thus reports First and Second-Order SHFMMs for the bit error pattern at the output of an Orthogonal Frequency Division Multiplexing based system for in-home narrowband PLC applications. Accurate SHFMMs have been derived for a residential and laboratory environment using the efficient iterative Baum–Welch algorithm. The log-likelihood ratio plots, the error-free run distribution plots, the mean square error and Chi-Square (χ2) test validates the accuracy of the derived models. The reliability and accuracy of resulting models are confirmed by a close match between the measured bit error sequences and the model generated bit error sequences. The estimated Second-Order SHFMMs have been validated to be superior to the First-Order models, although at the expense of more computational complexity. Resulting models assist designers to speed up and facilitate the process of designing and evaluating novelties for PLC systems.