Sobhy M. Abdelkader

Transmission Loss Allocation Through Complex Power Flow Tracing

This paper presents a new method for transmission loss allocation. The method is based on tracing the complex power flow through the network and determining the share of each load on the flow and losses through each line. Transmission losses are taken into consideration during power flow tracing. Unbundling line losses is carried out using an equation, which has a physical basis, and considers the coupling between active and reactive power flows as well as the cross effects of active and reactive power on active and reactive losses. A tracing algorithm which can be considered direct to a good extent, as there is no need for exhaustive search to determine the flow paths as these are determined in a systematic way during the course of tracing. Results of application of the proposed method are also presented.

Online Tracking of Thévenin Equivalent Parameters Using PMU Measurements

This paper presents a new method for tracking Thévenin equivalent parameters for a power system at a node using local phasor measurement unit (PMU) measurements. Three consecutive phasor measurements for voltage and current, recorded at one location, are used. The phase drifts caused by the measurement slip frequency are first determined and phase angles of the measured phasors are corrected so that the corrected phasors are synchronized to the same reference. The synchronized phasors are then used to determine the equivalent Thévenin parameters of the system.

Characterization of Transmission Losses

In this paper, characterizing transmission losses according to their origin is carried out. Transmission loss is decomposed into three components. The first is due to the current flow from generators to loads. The second is due to the circulating current between generators. The third represents the contribution of network structure and controls to increasing or decreasing transmission losses. Analytical proofs of the proposed loss decomposition are presented along with methods of allocating each component to the parties contributing to it. Illustration on simple dc and ac systems is presented. Results of application of the proposed method compared with other methods are also presented.

Online Thévenin Equivalent Determination Considering System Side Changes and Measurement Errors

This paper presents a new method for online determination of the Thèvenin equivalent parameters of a power system at a given node using the local PMU measurements at that node. The method takes into account the measurement errors and the changes in the system side. An analysis of the effects of changes in system side is carried out on a simple two-bus system to gain an insight of the effect of system side changes on the estimated Thévenin equivalent parameters. The proposed method uses voltage and current magnitudes as well as active and reactive powers; thus avoiding the effect of phase angle drift of the PMU and the need to synchronize measurements at different instances to the same reference. Applying the method to the IEEE 30-bus test system has shown its ability to correctly determine the Thévenin equivalent even in the presence of measurement errors and/or system side changes.

Complex power flow tracing for transmission loss allocation considering loop flows

This paper presents a new method for transmission loss allocation based on complex power flow tracing. Building on previous works of the author, the paper presents a generalized model for the transmission line, which is used as the building block for the complex power flow tracing algorithm. The developed line model is similar to the famous generalized circuit constants, ABCD, model. While the ABCD line model relates voltage and current at one end of the line to those at the other end, the developed line model relates the partial flows caused by a load/generator at the receiving/sending end of the line to the partial flows caused by that load/generator through all lines following that line in the upstream/downstream direction. The proposed model has properties regarding series and parallel equivalence similar to those of the ABCD model. The only difference is that the proposed model parameters are determined based on the line flows whereas the ABCD parameters are functions of line constants. Although the power flow tracing algorithm employed is similar to the previously proposed by the author, the modification introduced in this paper enables more insight to the loss allocation process as the cross effects of active and reactive power flows on both active and reactive losses can be quantified more clearly. The paper also describes a method for loss allocation in the presence of loop flows based on signal flow graph manipulation techniques.

A method for determining generators’ shares in loads, line flows and losses

Abstract This paper presents a new method for calculating the individual generators’ shares in line flows, line losses and loads. The method is described and illustrated on active power flows, but it can be applied in the same way to reactive power flows. Starting from a power flow solution, the line flow matrix is formed. This matrix is used for identifying node types, tracing the power flow from generators downstream to loads, and to determine generators’ participation factors to lines and loads. Neither exhaustive search nor matrix inversion is required. Hence, the method is claimed to be the least computationally demanding amongst all of the similar methods.

Modelling and prediction techniques for dynamic overhead line rating

Due to the deregulation of the power supply industry and the continuing need for network expansion, there is pressure to maximize utilization of the existing transmission and distribution networks. Compared to the traditional static line rating, a dynamic line rating identifies the ampacity in real time according to the measured weather conditions, taking the wind cooling effect into account that allows extra power to be accommodated. The physical modelling techniques established in IEEE and CIGRE standards are based on the physical relationships of the conductor, which require a number of predetermined parameters and engineering judgements. Therefore, this paper compares different modelling approached, including the statistical and Artificial Intelligent models, which only require the monitored data to be collected. Also, the variability of local weather within a short period has been assessed that it is proven that these two methods have the ability to forecast the future conductor temperature based on present measured data and forecasted current.

Statistical Analyses of Wind and Solar Energy Resources for the Development of Hybrid Microgrid

In this paper, a procedure for the statistical analyses of wind and solar energy resources are investigated in order to determine the accurate frequency distribution for the development of hybrid microgrid. The frequency distributions used for wind speed data analysis include Weibull, Rayleigh and Gamma distribution functions. On the other hand the frequency distributions used for the analysis of solar radiation data include Weibull, Logistics, lognormal, Beta and Gamma functions. The performance of the probability distributions used in the wind speed analyses are based on the error evaluations between the predicted and the theoretical wind power densities of the site. Similarly, the performance of the probability distribution functions used in the solar radiation data were judged based on Kolmogorov-Smirnov, Anderson-Darling and Chi-Square tests. The goodness of fit tests (GOF) results of the wind speed analyses show that Weibull distribution performed better compared to Rayleigh and Gamma distributions. On the other hand Beta distribution fitted the solar radiation data better than all other distributions models.

Partial least squares modelling for dynamic overhead line ratings

Due to the deregulation of the power supply industry and the continuing need for network expansion, there is pressure to maximize utilization of the existing transmission and distribution networks. Compared to the traditional static line rating, a dynamic line rating provides a more accurate methodology to determine the ampacity of the overhead line in real time. Taking the wind cooling effect into account allows extra power to be accommodated. Line-rating methodologies developed based on IEEE and CIGRE standards are widely employed for dynamic line ratings. However, there are a number of parameters that need to be chosen for each line which can lead to errors in the temperature/ampacity prediction. In comparison, the statistical technique, partial least squares (PLS) regression, only requires the monitored data to be collected. The model coefficients are determined by processing the data sets over a period, such as one year. In this paper, both physical (CIGRE) and statistical (PLS) models are analyzed using the data collected from field testing, and the comparisons of the two models are also demonstrated.

Algorithm for Transmission Loss Allocation in Market-Based Power Systems with Wind Generation

AbstractThis paper proposes a novel method for transmission loss allocation in restructured power systems. It is based on circuit laws and the orthogonal projection theory. In this method, the current flow in each branch is divided into two components. The first one is due to the power transfer from generators to loads. The second component is due to the voltage differences between generators’ buses. The later currents are called no-load or circulating currents. These two current components are computed by using the superposition principle. The contribution of each load and generator to power losses in each branch of the network is derived analytically. Hence, the share of each load or generator in the overall transmission network losses is estimated. Furthermore, the impact of bilateral and multilateral contracts is incorporated in the power loss allocation algorithm. The contribution of each contract to the total transmission system power loss is estimated accurately. The method also takes into account ...