Ping Lam So

Modeling of transfer Characteristics for the broadband power line communication channel

This paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. In this approach, the power line is approximated as a transmission line and the two intrinsic parameters, the characteristic impedance and the propagation constants, are derived based on the lumped-element circuit model. Using these intrinsic parameters, the transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. Detail derivation of this line model is given in this paper. The model has been verified with practical measurements conducted on actual power networks. It is demonstrated that the model accurately determine the line characteristics under different network configuration and when different household appliances are connected.

Performance analysis of OFDM systems for broadband power line communications under impulsive noise and multipath effects

The impulsive noise and multipath effects are the main reasons to cause bit errors in power line communications. In this paper, the bit error rate (BER) performance of the orthogonal frequency division multiplexing (OFDM) system under the impulsive noise and multipath effects are theoretically analyzed in terms of closed form formulas. Through the analysis, it is shown that OFDM can mitigate the adverse effect of the impulsive noise and only the heavily disturbed impulsive noise will interfere the BER performance of the OFDM system. It is also shown that the adverse effect of multipath is more serious than that of impulsive noise. In this paper, the guard interval is used to improve the BER performance of the OFDM system. As the longer guard interval is inefficient in using the signal power, the optimum guard interval that can achieve the best BER performance is studied.

Improvement of power quality using adaptive shunt active filter

Problems caused by power quality have great adverse economical impact on the utilities and customers. Current harmonics are one of the most common power quality problems and are usually resolved by the use of shunt passive or active filters. In this paper, a new control design using artificial neural networks is proposed to make the conventional shunt active filter adaptive. The proposed adaptive shunt active filter can compensate for harmonic currents, power factor and nonlinear load unbalance. A self-charging technique is also proposed to regulate the dc capacitor voltage at the desired level with the use of a PI controller. The design concept of the adaptive shunt active filter is verified through simulation studies and the results obtained are discussed.

Coordinated Control of Distributed Energy-Storage Systems for Voltage Regulation in Distribution Networks

In this paper, distributed energy-storage systems (ESSs) are proposed to solve the voltage rise/drop issues in low-voltage (LV) distribution networks with a high penetration of rooftop photovoltaics (PVs). During the peak PV generation period, the voltages are mitigated by charging the ESSs, and the stored energy is discharged for voltage support during the peak load period. The impact of storage devices integrated with the PV source on feeder voltages is investigated in detail. A coordinated control method, which includes distributed and localized controls, is proposed for distributed ESSs. The distributed control using the consensus algorithm regulates the feeder voltages within the required limits, while the localized control regulates the state of charge (SoC) of each ESS within the desired SoC range. The entire control structure ensures voltage regulation while effectively utilizing storage capacity under various operation conditions. The proposed control method is evaluated in LV distribution networks, and the simulation results validate the effectiveness of this method.

Radio-frequency common-mode noise propagation model for power-line cable

Electromagnetic-interference (EMI) radiation from a power-line communications (PLC) network has been a major concern for the widespread use of broadband PLC technology. It is also well known that the dominant radiation mode of the PLC network is common mode (CM) by nature. Therefore, for electromagnetic-compatibility planning purposes, knowledge of the CM noise propagation path of the power line in the frequency range of 1 to 30 MHz is essential to provide insight of EMI radiation emitted by the power line. Based on a two-current-probe measurement approach, the CM noise propagation model for a three-wire power-line cable can be derived and represented by an equivalent two-wire CM transmission line. The equivalent CM noise propagation model allows us to predict the CM noise current on the power line with reasonable accuracy. The model will serve as a valuable tool in the future to identify effective ways to suppress EMI radiation from the PLC network.

Modeling and Performance Analysis of Automatic Meter-Reading Systems Using PLC Under Impulsive Noise Interference

This paper presents analytical models to study the performances of two schemes for automatic meter-reading (AMR) systems using power-line-communication (PLC)-access networks. These two schemes, namely, clustered simple polling and neighbor relay polling, are shown to be typically effective and efficient AMR schemes for overcoming the “silent node” problem associated with AMR systems. The analytical models also present the analysis of two different topological structures, radial and tree, of the PLC-access network assuming an automatic three-level clustering mechanism. The performances of the AMR schemes in terms of data-collection delay and throughput under impulsive noise interference are analyzed. The models are used to study the optimum packet size and data rate to mitigate the effect of impulsive noise on AMR system performance. Through comparison of the analytical results with the simulation results, it is verified that the analytical models have been accurately developed.

Comparison of CDMA and OFDM Systems for Broadband Power Line Communications

Direct sequence code division multiple access (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) systems are two options for broadband power line communications. In this paper, a comparison is made between the CDMA and OFDM systems. The bit error rate (BER) performance and the optimum overall data rate of the CDMA and OFDM systems are analyzed and compared, using the criteria of the same bandwidth occupation, the same transmission power for each user, the same total number of users in the system and the same power line channel. The comparison is based on the analytical models that are developed and verified by simulations.

Modeling and Analysis of Common-Mode Current Propagation in Broadband Power-Line Communication Networks

This paper proposes a new approach to modeling the common-mode (CM) current propagation path of electrical power-line cables for broadband power-line communications (PLC). In this approach, a CM current propagation model for a three-wire power-line cable is developed using the multiconductor transmission-line theory. The model is used to study the electromagnetic-interference radiation mechanism from the PLC network in the frequency range of 1 to 30 MHz. The accuracy of the model is verified through numerical simulations and practical measurements conducted on the actual power-line network. The developed model allows us to predict the CM current in the power-line cable with reasonable accuracy.

A New Routing Protocol for PLC-Based AMR Systems

This paper proposes a new and effective communication protocol for the implementation of an automatic meter reading system using power-line communications (PLC) and presents analytical models to study its performance. The proposed protocol utilizes a novel packet routing system which combines “Request” and “Data” packets that enable meter units to send their metering data to the data concentrator and, at the same time, re-broadcast the “Request” to other meter units. It employs a carrier-sense multiple access with collision avoidance medium-access control protocol for the contention-based data transmission. The performance of the proposed protocol in terms of data-collection delay and throughput under impulsive noise interference is analyzed and compared with that of the neighbor relay polling (NRP) protocol. The proposed protocol does not require a central controller to initiate all data transmission unlike polling-based protocols and can be applied to PLC systems with unstructured networks. The proposed protocol ensures significantly lower data-collection delay than the NRP protocol. It will be able to achieve 100% throughput for light and moderate impulsive noise environments and 75% throughput for a heavy impulsive noise environment using broadband PLC with a cluster size larger than 60.

Common-Mode Current Propagation in Power Line Communication Networks Using Multi-Conductor Transmission Line Theory

This paper proposes a new approach to model the common-mode (CM) current propagation path of electrical power line cable for broadband power line communications (PLC). In this approach, a CM current propagation model for a three-wire power line cable is developed using the Multi-conductor Transmission Line (MTL) theory. The model is used to study the electromagnetic interference (EMI) radiation mechanism from the PLC network. The accuracy of the model is verified through numerical simulations and practical measurements conducted on the actual power line network. The developed model allows us to predict the CM current in the power line cable with reasonable accuracy.