Essam El-Din Abou El-Zahab

LC compensators for power factor correction of nonlinear loads

A method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor, and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical examples.

LC compensators based on cost minimization for nonlinear loads

This paper describes an optimization method for the evaluation of the parameters of the LC compensator for nonlinear loads taking into account cost constraints. The solution will be obtained with an optimization algorithm based on the reduced gradient technique which will locate the maximum power factors by searching along the constant-cost power factor ridges, for the point where the gradient of the transmission loss is zero.

Simple neuro-controller with a modified error function for a synchronous generator

A simple neuro-controller for a synchronous generator is presented in this paper. The controller consists of a single neuron trained on-line using the back propagation algorithm based on a modified error function. The modified error function uses the controlled variable and its derivatives. Based on the variables used in the modified error function, the controller performs the functions of terminal voltage control and power system stabilizer. Simulation studies for a single-machine and multi-machine power system environment are presented to demonstrate the effectiveness of using the simple neuro-controller.

Power conditioning using dynamic voltage restorers under different voltage sag types

Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

Comparing capacitive and LC compensators for power factor correction

A method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical example.

Practical considerations on power factor correction for nonlinear loads

The choice of LC compensator may be constrained by the availability of manufactures units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical example.

Effect of connecting shunt capacitor on nonlinear load terminals

The use of terminal shunt capacitance has different effects on the displacement factor and distortion factor components of the power factor. These effects are considered for nonlinear loads with ideal supply, and also where the supply impedance exists but is small compared with the load impedance. Optimization of the displacement factor is found to result in reduction of the distortion factor to a minimum value.

Practical considerations regarding power factor for nonlinear loads

The choice of LC compensator may be constrained by the availability of manufacturers units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical examples.