Zakariya Al-Hamouz

A new load frequency variable structure controller using genetic algorithms

Abstract In this paper, selection of the variable structure controller (VSC) feedback gains by genetic algorithms (GA) is presented contrary to the trial and error selection of the variable structure feedback gains reported in the literature. This is considered as one of the main underlying problems associated with VSC. The proposed method provides an optimal and systematic way of feedback gains selection in the VSC. To test the effectiveness of the new selection method, the proposed design has been applied to the load frequency problem of a single area power system. The system performance against step load variations has been simulated and compared to some previous methods, Simulation results show that not only the dynamic system performance has been improved, but also the control effort is dramatically reduced.

Ground water coagulation using soluble stainless steel electrodes

Abstract This study dealt with colloids separation from ground water in the Eastern Province of Saudi Arabia. The water was found to have a conductivity of 4400 μs/cm and chloride and sulfate concentrations of 834 and 550 mg/l, respectively. The turbidity of the water was increased to 76 nephlometric turbidity unit (NTU) by the addition of bentonite. The efficiency of using soluble stainless steel electrodes for the in-situ formation of ferric hydroxide has been investigated. The electrical current input was found to be inversely proportional to the residual turbidity in the test water. At a contact time of 5 min and a natural chloride content, the highest turbidity removal efficiency of 95% was achieved at a current of 1 A. When the current was reduced to 0.5 A and the contact time was increased to 10 min, the residual turbidity was reduced from 4.0 to 1.6 NTU. Furthermore, similar turbidity removals were achieved at a much shorter contact time (2 min) when 1 g/l sodium chloride was added to the test water. Due to the importance of pH variation with regard to coagulation, the phenomenon of voltage-induced hydrogen evolution was investigated as well. While the solutions final pH increased with the increase in current and contact time, it decreased with the increase in sodium chloride concentration.

Analysis of monopolar ionized field as influenced by ion diffusion

This paper aims at the analysis of the monopolar ionized field in conductor-to-plane configurations without resorting to Deutschs assumption. A new iterative finite-element technique is proposed to solve Poissons equation. Satisfying the current continuity condition and updating the space-charge density are based on the application of Kirchoffs current-balance law at each node of the finite-element grid and take the ion diffusion into account. The proposed method of solution has been applied for laboratory and full-scale models of a monopolar transmission line. The calculated V-I characteristics, the current-density, and electric field profiles at the ground plane agreed well with those measured experimentally in comparison with previous calculations. Fast convergence and simplicity in programming characterize the proposed method. >

Variable structure load frequency controllers for multiarea power systems

Abstract In this paper, variable structure load frequency controllers (VSLFC) are proposed for interconnected power systems. Two designs are presented: the optimal variable structure load frequency controller (OVSLFC) and the pole placement variable structure load frequency controller (PPVSLFC). The choice of the controllers switching vectors is based on local information and accessible state variables. The effectiveness of the proposed controllers is demonstrated through their application to two-area and three-area interconnected power systems. The results reveal that there is a significant improvement in the system dynamic performance with VSLFC over that with an integral controller. Moreover, the performance of the system using the proposed controllers was found to be quite insensitive to the system parameters uncertainties.

Finite-element analysis of monopolar ionized fields including ion diffusion

This paper aims at analysis of the monopolar ionized field in conductor-to-plane configurations. An iterative finite-element technique is used to solve Poissons equation. Two algorithms are proposed for satisfying the current continuity condition and updating the space-charge density. The first algorithm is a modified method of characteristics, which neglects ion diffusion. The second algorithm is based on application of Kirchhoffs current-balance law at each node of the finite-element grid and takes ion diffusion into account. The proposed method of solution has been applied for laboratory and full-scale models of monopolar transmission lines. The calculated V-I characteristics, current-density and electric field profiles at the ground plane agreed well with those measured experimentally in comparison with previous calculations. Fast convergence and simplicity in programming characterize the proposed method.

Corona power loss, electric field, and current density profiles in bundled horizontal and vertical bipolar conductors

In this paper, computation of the corona current and, hence, the corona power loss associated with bipolar high-voltage direct current (HVDC) conductors is presented using the finite-element method (FEM) and the method of characteristics (MOC). The former method is used to solve Poissons equation while the latter is used to satisfy the current continuity condition. The ground-plane current density and electric field profiles associated with the HVDC conductors are also calculated as a prerequisite for the computation of the corona current. The effectiveness of the present method is demonstrated using HVDC full-scale and laboratory-model transmission lines. Horizontal and vertical bipolar configurations are tested with 2 and 4 bundles. Comparison between previously measured and computed profiles and present calculations shows satisfactory agreement with previous measured and calculated values.

A new finite-element analysis of an ionized field in coaxial cylindrical geometry

This communication aims at the analysis of a unipolar ionized field. An efficient iterative method that uses the finite element technique (FET) as a numerical tool is proposed. The method seeks a solution to only one second-order partial differential equation (PDE) rather than a solution to a nonlinear third-order PDE or a solution to two simultaneous second-order PDES. The effectiveness of the proposed method has been tested through application to the coaxial cylindrical geometry where the ionized field has been evaluated analytically. The voltage value at the stressed conductor as well as the constancy of the field at the onset value around the conductor represent the boundary conditions of the proposed method, which is characterized by quick convergence to achieve the accuracy and simplicity required for computer programming.

A combined algorithm based on finite elements and a modified method of characteristics for the analysis of the corona in wire-duct electrostatic precipitators

This paper numerically analyzes corona power loss associated with wire-duct electrostatic precipitators. The finite-element method is used to solve Poissons equation and a modified method of characteristics is used to satisfy the current continuity condition. The two methods are repeated iteratively to obtain a self-consistent solution of the describing equations. The effectiveness of this approach is tested by comparing the computed results with previously obtained experimental and calculated values. The agreement with experimental results is found to be satisfactory.

Transmission expansion planning using nonlinear programming

A modified formulation of the transmission expansion planning (TEP) problem is proposed by revising the objective function and operating constraints to include the corona power loss term. Consequently, the objective function includes the cost of investment of transmission lines, the ohmic power loss as well as the corona power loss, which reveals a highly nonlinear objective function. Hence, the nonlinear programming or the non-convex optimization techniques are utilized to solve such large-scale practical problems. The new formulation has been applied to the well-known Garvers 6-bus system. It has been found that for a range of tariffs of kWh, the total cost of the expanded network (when including the corona power loss) is less than that when excluding this new term. Comparison with previously reported work is also included.

Electrochemical Treatment of Nitrite Using Stainless Steel Electrodes

The efficiency of nitrite removal in an electrochemical cell was investigated in this study using stainless steel electrodes. The experiments were designed to study the effects of current input, volume of the solution, initial pH, and number of electrodes on removal of nitrite at a concentration typical to aquaculture system effluents. Current variation causes opposite trends, while an increase in current would increase the oxidizing efficiency of the system, the voltage induced increase in pH due to hydrogen evolution would decrease the efficiency of the oxidizing agent formed. However, the highest nitrite removal was achieved at a current of 2 A and a complete removal was attained after a duration of ten minutes. A first order reaction model was developed to predict the effect of current on nitrite removal. The energy consumption was directly proportional to the initial pH and the solution volume, while it was inversely proportional to the number of electrodes.