HYBRID wireless/powerline communication has been proposed to improve reliability
and performance in smart grids. In this work we focus on a hybrid wireless/
narrowband PLC (WiNPLC) system for communication links in Smart
Grids (SG) such as the link between smart meters (SM) and in-home devices (IHD). An
effective approach to enhance the data rate in narrowband power line communication
(NB-PLC) system is multicarrier modulation based on orthogonal frequency-division
multiplexing (OFDM) and multiple-input multiple-output (MIMO) transmission over
multiple power line phases.
Low voltage, in-home NB-PLC networks allow direct communication between SM
and IHD. In order to minimize security issues, in many deployment scenarios transmission
takes place only towards the IHD to display consumption data, with no backwards
channel. As a result, channel estimation is difficult and a key challenge for achieving
reliable communication over NB-PLC is to use robust transmission and detection techniques
to mitigate effect of the impulsive noise within the PLC channel and recover
transmitted data. To this aim, it is fundamental to give an appropriate characterization
of such a noise. In fact, substantial components of the noise in NB-PLC systems
exhibit a cyclostationary behavior with a period of half the alternating current (AC)
cycle. Moreover, when MIMO transmission is adopted, an important issue that must be
considered is the cross-correlation between different phases.
Frequency-shift (FRESH) filter is a recently proposed approach that is able to reproduce
the effects of cyclostationary NB-PLC noise obtained from measurements.
In this work, we propose to classify the noise generated by FRESH filter into three
classes, based on the estimation of the respective probability density functions and
on the evaluation of their second order statistics. First, we show that while one class
exhibits a normal distribution, the other two exhibit an impulsive behavior for which
we propose a generalized Student’s t-distribution. Simulation results show that the bit
error rate (BER) of MIMO-OFDM NB-PLC significantly changes between different
classes of noise. Hence, we develop an algorithm for switching data delivery between
MIMO-OFDM NB-PLC and MIMO-OFDM wireless transmission in unlicensed frequency
band that takes into account knowledge of the periodicity of the three classes of noises. The result is a hybrid MIMO-OFDM wireless/NB-PLC system, which we
refer to as, hybrid MIMO-OFDM WiNPLC. Our simulation results demonstrate BER
improvement of the proposed hybrid system over individual MIMO-OFDM NB-PLC
or MIMO-OFDM wireless systems. Further improvement in performance of hybrid
system could be obtained by evaluating capacity of the MIMO NB-PLC system in presence
of different classes of the noise. This thesis obtained capacity by spatio-temporal
whitening of the cyclostationary correlated noise samples generated through FRESH
filtering. This capacity is useful for adapting the modulation order and obtaining optimum
performance based on the class of noise. Due to the cyclostationarity of the
noise, similar behavior is repeated in next periods and can take advantages of this preprocessing.
To support the future works of other researchers in the field of NB-PLC, we propose
a simple and more adaptive method to generate noise samples with characteristics similar
to those obtained using the FRESH filter. To this aim, filterbank of FRESH filter is
replaced by applying spectral and temporal shaping to a white Gaussian (WGN) noise
random process to obtain correlated impulsive noise samples. In addition, by changing
the slope of temporal shaping, distribution of each class could change from Gaussian
to impulsive and vice versa. The proposed noise generation approach is compared with
FRESH filter generator in terms of normalized mean square error (NMSE) in the cyclic
auto-correlation, and bit error rate (BER), between the measured and generated noise
samples.
The noise introduced by electrical appliances to the communication data could be
used as device signatures which is an useful information for energy monitoring. In this
regard, data received to all SMs must be collected and analyzed for improving energy
consumption management. Due to the notable rise in the number of installed SMs,
Non-Intrusive Load Monitoring (NILM) has received growing attention in the recent
years. NILM aims at replacing several SMs by a single SM and estimating the power
demand of individual appliances from a household’s aggregate electricity consumption.
In the present work, after reviewing different categories of household appliances, the
state-of-the-art load signatures, including both macroscopic and microscopic features,
are introduced. Next, commonly used supervised and unsupervised disaggregation algorithms,
which are employed to classify the appliances based on the extracted features,
are discussed. Publically accessible datasets and open-source tools, which have been released
in the recent years to assist the NILM research and to facilitate the comparison of
disaggregation algorithms, are then reviewed. Finally, main applications of energy disaggregation,
including providing itemized energy bills, enabling more accurate demand
prediction, identifying malfunctioning appliances, and assisting occupancy monitoring,
are presented.