Brian G. Stewart

A Methodology for Optimization of Power Systems Demand Due to Electric Vehicle Charging Load

This paper presents a methodology of optimizing power systems demand due to electric vehicle (EV) charging load. Following a brief introduction to the charging characteristics of EV batteries, a statistical model is presented for predicting the EV charging load. The optimization problem is then described, and the solution is provided based on the model. An example study is carried out with error and sensitivity analysis to validate the proposed method. Four scenarios of various combinations of EV penetration levels and charging modes are considered in the study. A series of numerical solutions to the optimization problem in these scenarios are obtained by serial quadratic programming. The results show that EV charging load has significant potential to improve the daily load profile of power systems if the charging loads are optimally distributed. It is demonstrated that flattened load profiles may be achieved at all EV penetration levels if the EVs are charged through a fast charging mode. In addition, the implementation of the proposed optimization is discussed with analyses on the impact of travel pattern and the willingness of customers.

Pilot-Assisted PAPR Reduction Technique for Optical OFDM Communication Systems

This paper investigates the use of a pilot signal in reducing the electrical peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) intensity-modulated optical wireless communication system. The phase of the pilot signal is chosen based on the selected mapping (SLM) algorithm while the maximum likelihood criterion is used to estimate the pilot signal at the receiver. Bit error rate (BER) performance of the pilot-assisted optical OFDM system is identical to that of the basic optical OFDM (with no pilot and no PAPR reduction technique implemented) at the desired BER of less than 10-3 needed to establish a reliable communication link. The pilot-assisted PAPR reduction technique results in higher reduction in PAPR for high order constellations than the classical SLM. With respect to a basic OFDM system, with no pilot and no PAPR reduction technique implemented, a pilot-assisted M-QAM optical OFDM system is capable of reducing the electrical PAPR by over about 2.5 dB at a modest complementary cumulative distribution function (CCDF) point of 10-4 for M = 64. Greater reductions in PAPR are possible at lower values of CCDF with no degradation to the systems error performance. Clipping the time domain signal at both ends mildly (at 25 times the signal variance level) results in a PAPR reduction of about 6.3 dB at the same CCDF of 10-4 but with an error floor of about 3 ×10-5. Although it is possible to attain any desired level of electrical PAPR reduction with signal clipping, this will be at a cost of deterioration in the systemss bit error performance.

A Comprehensive Performance Study of OPNET Modeler for ZigBee Wireless Sensor Networks

OPNET has been widely used as a network simulator, but not much emphasis has been given on the performance of this simulator for ZigBee wireless sensor networks (WSN). Simulation of WSNs is a challenging task due to the nature of hardware design, energy limitations, and deployment of a vast number of nodes. An inclusive study and analysis of the QoS performance evaluation of the ZigBee protocol within the OPNET simulator for different WSN topologies and routing schemes is presented here. Based on simulation and analysis of results this paper can be considered as a guide for researchers in evaluating OPNET Modeler as a WSN simulator for Zigbee networks. Some enhancements needed in OPNET Modeler to be more suitable for the simulation of ZigBee WSNs are discussed.

Comparisons of discrete wavelet transform, wavelet packet transform and stationary wavelet transform in denoising PD measurement data

Noise has been a major limitation to partial discharge (PD) measurement. It is crucial to suppress noise prior to any PD data analysis. Recent research shows that the discrete wavelet transform, wavelet packet transform and stationary wavelet transform techniques have all achieved good effect in noise rejection in PD measurement. This paper compares the effectiveness and computing time required of the three types of wavelet transform methods when applied to simulated PD data in presence of white noise and sinusoidal interference

Partial discharge current pulses in SF6 and the effect of superposition of their radiometric measurement

The practical advantages of employing non-contact radio frequency (RF) methods for detecting partial discharges (PDs) in high voltage equipment have led to significant effort being focused on the diagnosis of electrical plants using RF techniques. This has particularly been the case for gas insulated substations, which use sulphur hexafluoride (SF6) as an insulating medium. One of the most important challenges facing RF diagnostics is the problem of relating the RF emissions to some measure of severity of the PD. Previous work has established that the amplitude or energy of RF signals radiated from a PD source is strongly dependent on the rate of change of current in the PD pulse. In this paper, measurements of PD current pulses in SF6 are presented for a point-plane configuration using an extremely wide bandwidth (13 GHz) measurement system. By this means, PD pulse shapes have been recorded with better resolution than has previously been possible and rise times have been measured with a high degree of accuracy. The results show a considerable variation in pulse shape, with the minimum rise time measured being 35 ps. With this high time-domain resolution, we have been able to distinguish features within the PD pulses that will affect the energy of the radiated RF signal. In particular, the current pulses tend to occur in bursts of up to ten individual pulses in as little as 1 ns, which will excite multiple RF signals in rapid succession. The effect of superposition of RF waveforms has been investigated by studying the variation in detected RF energy with respect to the time delay between PD pulses. It was found that when two PDs occur within a short period (< 150 ns) the combined energy of the resulting RF pulse has the potential to vary by ±30% of that resulting from two equivalent PD pulses with a wider pulse spacing ( 150 ns). In terms of a practical monitoring system concerned with order-of-magnitude variations; this is not considered to pose a major problem for the RF technique.

Congestion adaptive multipath routing for load balancing in Mobile Ad hoc Networks

Congestion control and load balancing have been challenging tasks in Mobile Ad hoc Networks (MANET) due to the dynamic and un-predictable behaviour and topology change of such networks. For effective load balancing and congestion control, routing metrics need to accurately capture the load in various locations of the network. In this paper, we present a congestion adaptive multipath routing protocol to increase the throughput and avoid congestion in MANETs. In our approach when the average load of an existing link increases beyond a defined threshold and the available bandwidth and residual battery energy decreases below a defined threshold, traffic is distributed over fail-safe multiple routes to reduce the traffic load on a congested link. Through simulation results, we show that our proposed approach achieves better throughput and packet delivery ratio with reduced delay for constant bit rate (CBR) traffic when compared with QMRB, a protocol using mobile routing backbones.

Network Coding-Based Block ACK for Wireless Relay Networks

This paper considers block acknowledgement (BACK) mechanisms in wireless regenerative relay networks. Conventionally, a total of

Least Squares Interpolation Methods for LTE System Channel Estimation over Extended ITU Channels

(2N+1)

Triangulation and 3D location estimation of RFI and Partial Discharge sources within a 400kV substation

BACK packets are required in wireless regenerative

Frequency distribution of RF energy from PD sources and its application in combined RF and IEC60270 measurements

N