Ahmed F. Zobaa

A Decentralized and Cooperative Architecture for Optimal Voltage Regulation in Smart Grids

Optimal voltage regulation is one of the main issues to address in a Smart Grid context. In this domain, the application of traditional hierarchical control paradigms has some disadvantages that could hinder their application in Smart Grids where the constant growth of grid complexity and the need for massive pervasion of distribution generation systems require more scalable and more flexible control and regulation paradigms. To try and overcome these challenges, this paper proposes the concept of a decentralized nonhierarchal voltage regulation architecture based on intelligent and cooperative smart entities. This paper intends to bring two main contributions to the existing literature. The first is the definition of a decentralized architecture aimed at computing the actual value of the cost function and its gradient without the need of a central fusion center acquiring and processing all the sensor acquisitions. The second is the proposal of a distributed and cooperative optimization strategy aimed at identifying the optimal asset of the voltage controllers.

Optimal

In its broadest sense, passive filters have been a very potent technique for power system harmonic suppression because of their possible different frequency response characteristics that can achieve a certain required harmonic filtering target, also due to their simplicity and economical cost. This paper presents an application of FORTRAN feasible sequential quadratic programming to find the optimal sizing of parameters of C-type passive filters for minimizing the total voltage harmonic distortion of nonlinear loads, where maintaining a given power factor at a specified range is desired. The optimal design of the C-type passive filter as an alternative to the conventional passive filtering techniques is introduced, and a detailed comparison of the results between an uncompensated system and a C-type filter are discussed by means of different numerical examples, considering source and load nonlinearities, while taking into account compliance with the IEEE standards 519-1992 and 18-2002.

C

The development of new passive, active, and hybrid filtering techniques is important; and the issues of higher quality, reduced complexity, higher efficiency, and lower cost are important conditions that need to be addressed with regard to the expected stringent trends in power quality obligations. This paper suggests a new approach for the optimal sizing of hybrid active power filter (HAPF) parameters, which is presented for three-phase industrial power systems. Hybrid filter topology can be used to compensate harmonic currents, as well as for power factor corrections, without concern for importing and exporting harmonics, or simply the series and parallel resonance that may occur. The new trend in harmonic power filter design is not to obtain the best solution from a single objective optimization but to obtain a good compromise solution accomplished under other conflicting objectives. Fortran Feasible Sequential Quadratic Programming is used to determine the proposed filter optimal sizing to minimize the total voltage harmonic distortion as the main objective function, where maintaining the load power factor at an acceptable limit is desired. If the total harmonic voltage distortion achieves the specified goal, then the objective is redirected into minimizing the resultant voltage and current total harmonic distortions. The optimal design of the HAPF is analyzed by means of three case studies.

-Type Passive Filter Based on Minimization of the Voltage Harmonic Distortion for Nonlinear Loads

Design and successful operation of wind energy conversion systems (WECs) is a very complex task and requires the skills of many interdisciplinary skills, e.g., civil, mechanical, electrical and electronics, geography, aerospace, environmental etc. Performance of WECs depends upon subsystems like wind turbine (aerodynamic), gears (mechanical), generator (electrical); whereas the availability of wind resources are governed by the climatic conditions of the region concerned for which wind survey is extremely important to exploit wind energy. This paper presents a number of issues related to the power generation from WECs e.g. factors affecting wind power, their classification, choice of generators, main design considerations in wind turbine design, problems related with grid connections, wind-diesel autonomous hybrid power systems, reactive power control of wind system, environmental aspects of power generation, economics of wind power generation, and latest trend of wind power generation from off shore sites.

Optimal multiobjective design of hybrid active power filters considering a distorted environment

Distributed power generation is the future trend due to its ability to accommodate variety of renewable/alternative energy sources, its potential to improve the energy efficiency and power system capability, and its promise for power reliability and security. Many distributed energy sources exists such solar energy, fuel cell, micro turbine, and wind energy. Distributed power generation concept has been implemented in various places with various degree of complexity. A comprehensive review on the distributed power generation is presented in this paper

Some Issues Related to Power Generation Using Wind Energy Conversion Systems: An Overview

In view of many problems associated with harmonics pollution within industrial firms, the development of new passive and/or hybrid filtering techniques of higher quality, higher efficiency, and lower cost is a necessity for the forthcoming power quality age. This article suggests a hybrid passive filter, which consists of a certain combination of a shunt passive filter (SPF) with a series passive portion as a substitute to overcome the shortcomings of conventional shunt passive filtering techniques. Constrained optimization is used to find the optimal sizing of parameters of the hybrid passive filter in order to reduce both harmonic voltages and harmonic currents in the power system to an acceptable level, as well as to improve the load power factor. The optimal design of the hybrid passive filter and its feasibility are compared with those of the C-type passive filter and the conventional SPF by means of four study cases taken from existing publications. Several simulation results are shown in order to highlight the viability of the proposed filter.

A comprehensive review on distributed power generation

Abstract The existence of harmonics in power systems and their effects have led to opulent issues of electric power quality. In this article, an optimization approach using FORTRAN feasible sequential quadratic programming to maximize the power factor at the DC drive loads terminals is presented using different passive filter topologies. Many constraints are taken into consideration such as series/parallel resonance conditions, effect of the supply frequency, and non-linearities of the supply and the load. Also, a detailed comparison of the simulated results for shunt- and series-passive filters is also presented in this article. The general compensation characteristics and the detailed comparison are discussed by means of different numerical examples from previous publications.

A New Approach for Harmonic Distortion Minimization in Power Systems Supplying 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.

Comparison of Shunt-passive and Series-passive Filters for DC Drive Loads

Potential applications of probabilistic modeling of current and voltage harmonics concern many aspects of power system engineering as accurate prediction of power system harmonic behavior provides important information to utility companies and equipment designers. In this paper, a method of reducing the expected value of the total voltage harmonic distortion for a specified range of source impedance values at different buses by using LC compensators, where it is desired to maintain a given power factor at a specified value, is presented. The criterion is based on mean value estimation of source and load characteristics, which are enabled by sampling measurements performed on the examined electrical plant as well as statistical analysis.

LC compensators for power factor correction of 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.