Taleb Moazzeni

Performance evaluation of a narrowband power line communication for smart grid with noise reduction technique

Performance of the narrowband power line communication (PLC) is significantly degraded by the impulsive noise with very large amplitudes and short durations. In practical applications, the simple memoryless nonlinearity techniques (Clipping, Blanking, and Clipping/Blanking) are often used in order to mitigate the effect of the impulsive noise. In this paper, we propose an optimal Clipping/Blanking technique for impulsive noise reduction in narrowband (9-490 kHz) PLC system. This optimal technique is based on the minimum bit error rate (BER) search. To this end, we have derived the transfer function of a typical low voltage (LV) PLC network using the common bottom-up approach and scattering matrix method. Our simulation results, in terms of BER versus signal to noise ratio (SNR), show that the proposed technique slightly improves the BER performance of the narrowband PLC system for smart grid applications and two-way communication between smart meters and utilities1.

Impulsive noise reduction of a narrowband power line communication using optimal nonlinearity technique

In this paper, we propose an optimal Clipping/Blanking nonlinearity technique for impulsive noise reduction in narrowband (9 kHz-490 kHz) PLC system. This optimal technique is based on the minimum bit error rate (BER) search. For our simulation, we have derived the transfer function of a typical low voltage (LV) PLC network using the common bottom-up approach and scattering matrix method. Our simulation results, in terms of BER versus signal to noise ratio (SNR), show that the proposed technique improves the BER performance of the narrowband PLC system.

A channel model for power line communication in the smart grid

Although Power Line Communication (PLC) is not a new technology, its use to support communication with low rate on low voltage (LV) distribution networks is still the focus of ongoing research. In this paper, we propose a PLC channel modeling method based on the bottom-up approach for LV PLC in a narrow, low frequency band between 9 kHz and 490 kHz. We employ the model to derive the transfer function of a typical LV PLC network, which is comprised of two common cable types (copper cables and aluminum conductor steel reinforced). We then investigate the multipath effect of the LV PLC in the studied low frequency bandwidth using numerical computations. Our simulation results based on the proposed channel model show an acceptable performance between neighboring nodes, in terms of bit error rate versus signal to noise ratio, which enables communication required for smart grid applications. Furthermore, we show that data transmission beyond one-hop communication in LV PLC networks will have to rely on upper layer protocols.

Flow Rate Measurement in a High-Temperature, Radioactive, and Corrosive Environment

The transit time of a thermal signal traveling along with a liquid flow can be obtained using a cross-correlation method. This transit-time-based flowmeter using thermocouples with grounded stainless steel shielding is by far the most robust and reliable solution to measure the flow rate in a harsh environment of high temperature, irradiation, and corrosion, typically seen in a nuclear reactor. In practice, cross-correlation calculation tends to produce flat peak plateau or multiple peaks, leading to a significant error in peak detection. To overcome this problem, in this paper, an autoadaptive impulse response function (AAIRF) estimation technique is thus introduced, and a significantly narrower peak is shown theoretically and also verified experimentally. In addition, we show that more accurate results can be obtained if a moving-average-filter-based cross-correlation function is combined with AAIRF. In this paper, we also investigate a few important practical problems related to negative delays and sampling frequencies of the data acquisition.

Measurement and Calibration of Thermal Cross-Correlation-Based Flowmeter Operating in Harsh Environment

In the harsh environment present in nuclear reactors, due to degradation caused by corrosion and/or erosion, the available nonintrusive flow rate measurement devices are capable of working only for a short period of time. The transit-time-based flowmeter using thermocouples (TC) with grounded stainless steel shielding is by far the most robust and reliable solution to this problem. This method suffers from a few signal processing problems, such as flat peak plateau or multiple peaks that result in wrong transit-time estimation. We have previously introduced a signal processing technique to correct the transit time estimation. However, as we conducted experiments, the calculated flowrates using the estimated transit-time are not in good agreement with readings from a standard flowmeter. To adjust the calculated flow, in this paper, we apply a regression method through the calibration process with measurements obtained from a standard flowmeter using an in-house developed apparatus. We observe a nearly linear relationship between the readings from the standard flowmeter and those from our flowmeter for flowrates ranging from 0.5-3 gpm (gallon per minute). The calibration results are quite consistent across different experiment scenarios.

On the Compactness of OFDM and Hermite Signals

In this letter, the compactness of the orthogonal frequency division multiplexing (OFDM) and orthogonal Hermite signals is compared by measuring their time-bandwidth products (TBPs). In a theory, it has been shown that the Hermite functions provided the minimum possible TBP among all orthogonal functions; however, this minimum is obtained from the root mean square sense, which is not useful for most communication applications. For instance, an OFDM system that usually employs rectangular pulses in time domain, the whole time duration of the pulses, is considered. In this letter, we use pulse energy criterion, i.e., 99% of the energy, in our measurements, and propose an empirical model as well as a theoretical equation for the TBP of these signals and show that the Hermite signals will still be more compact than OFDM signals. To make a fair comparison, we employ Hermite functions in an orthogonal signal multiplexing system as in OFDM, where trigonometric waveforms are employed as orthogonal basis.

Algorithms for the measurement of liquid metal coolant flow velocity with correlated thermal signals

The flow velocity of liquid metal coolant can be determined through the measurements of temperature fluctuation recorded by a pair of temperature sensors placed certain distance apart along the flow. Traditionally, this was done using a cross-correlation algorithm to estimate the transit time of the coolant, and thus its velocity. This widely used cross-correlation algorithm, however, suffers from the ambiguity in reading of measurements. To alleviate this problem, the transfer function estimation approach was recently proposed which tends to give more accurate results. In this paper, we introduce a new algorithm that can further improve the accuracy in the transit time estimation using an adaptive inverse system model at a higher cost of computation. When real-time computation is a concern, we propose a second algorithm based on an adaptive filtering approach which makes a sound trade-off between accuracy and computation cost. This algorithm incurs less processing time than the first proposed algorithm with higher accuracy than the two aforementioned conventional algorithms.

Data-classification-based SNR estimation for linearly modulated signals

We present a new numerical approach to SNR estimation of linearly modulated signals after passing through a complex additive white Gaussian noise (AWGN) channel. This classified data (CD) based SNR estimator is particularly suitable for both constant and non-constant modulus constellations, including BPSK, M-PSK and M-QAM. In essence, the received data will be first classified into a number of classes, and then a look-up table (LUT) is searched to find an entry that closest matches with the classified data; this matched result in LUT corresponds to the SNR value of the received data. The performance of the proposed estimator in terms of accuracy and complexity is evaluated by numerical simulations and compared with a few well-known estimators such as moment and maximum likelihood based estimators.

Numerical Simulation of Thermal Transit-Time Flow Meter for High Temperature, Corrosive and Irradiation Environment

In the environments of high temperature (>300 °C – 1000 °C), corrosive and even irradiation application, the challenges of providing reliable and accurate flow rate measurement is significant. In comparing with many other existing technologies for normal operation environments, correlated thermal transit-time flow meter show its advantages of resolving the challenges encountered in those harsh conditions. The correlated thermal signals can be detected by two separated thermal sensors (for example, thermocouples) in series alignment along the pipe, and derive the flow rate. It was evaluated to have accurate measurement for small pipe at slow fluid speed. In the higher flow rate and big pipe size application, this technology shows its weakness due to the limitations associated with slow response time of thermal sensor, dimension, and low strength of thermal signal. In this paper, we present a sophisticated layout of thermal transit-time flow meter with numerical simulation and experiments. By numerical results, we observed that the obtained flow in the bypass route is linearly proportional to the main flow over higher range of flows showing that the measured flow is successfully extended to high range and with stable and accurate measurement results.© 2013 ASME