Abderrazak Ouali

Application of a multiobjective evolutionary algorithm for optimal location and parameters of FACTS devices considering the real power loss in transmission lines and voltage deviation buses

In this paper, a multiobjective evolutionary algorithm (MOEA) to solve optimal reactive power (VAR) dispatch problem with flexible AC transmission system (FACTS) devices is presented. This nonlinear multiobjective problem (MOP) consists to minimize simultaneously real power loss in transmission lines and voltage deviation at load buses, by tuning parameters and location of FACTS. The constraints of this MOP are divided to equality constraints represented by load flow equations and inequality constraints such as, generation VAR sources and security limits at load buses. an unified power flow controller (UPFC) is considered. The design problem is tested on the IEEE 6-bus system.

Optimal design of multimachine power system stabilizers using evolutionary algorithms

In the past two decades, conventional power system stabilizer (PSS) is widely used to damp power systems oscillations. Nowadays, several approaches based on intelligent techniques have been applied to PSS design problem. This paper deals with optimal design of multimachine power system stabilizers to improve the dynamic stability of power system. The design problem is formulated as an optimization problem. Non-Dominated Sorting Genetic Algorithm (NSGA-II) is employed to search the optimal PSS parameters.. Based on a three-machine nine-bus test system, nonlinear simulation results under disturbance, show the effectiveness of the proposed approach in power oscillation damping.

Optimal location of multi type FACTS devices for multiple contingencies using genetic algorithms

With the electricity market deregulation, the number of unplanned power exchanges increases. If these exchanges are not controlled, some lines may become overloaded. Network contingencies often contribute to overloading of branches, violation of voltages and also leading to problem security. This paper presents a procedure based on the contingency severity index (CSI) described by a real power flow performance index (PI) to place multi type FACTS devices (Flexible AC Transmission System) in order to eliminate or alleviate the line over loads. TCSC(Thyristor Controlled Series Compensator) and UPFC(Unified Power Flow Controller) are considered and modeled for steady state analysis. Once the location is determined, their type, their optimal settings and cost of installation can be obtained by solving the optimization problem using genetic algorithms (GA). The proposed approach is tested on 9-bus test system.

Reduced order observer for permanent magnet synchronous generator in wind energy conversion system

This paper presents an approach to develop a simple reduced speed observer for permanent magnet synchronous generator (PMSG) in wind energy conversion system (WECS). The speed and rotor position estimation of the PMSG are obtained by only measuring phase voltage and current. Maximum wind energy extraction is achieved by running the wind turbine generator in variable-speed mode. The rotor speed is allowed to vary in sympathy with the wind speed by maintaining the tip speed ratio to the value that maximizes aerodynamic efficiency. Advantages of this mechanical sensorless control strategy for maximum power estimation are demonstrated by digital simulation of the WECS.

A vector control of a cascaded doubly fed induction generator for a wind energy conversion system

This paper presents a study developed about variable speed wind turbine system based on doubly fed twin stator induction machine (DFTSIG). In this paper we discuss the different architectures of the cascaded DFTSIG, in the case of direct coupling and indirect coupling. The wind generators modeling and control are presented; we have chosen a model with direct oriented vector control to ordering the power exchange between the machine stator controlled via a bidirectional converter. This control is developed and tested by synthesizing proportional integrator regulator.

A genetic algorithm PSS and AVR controller for electrical power system stability

In this paper genetic algorithm (GA) is applied in order to design a PSS/AVR controllers with the goal of improving both transient stability and voltage regulation of power system under a symmetrical three-phase short circuit fault. A comparison based on simulation is then performed between the proposed approach and the classical controllers (manual control, AVR with no PSS, AVR with PSS). The simulation results with a Single Machine Infinite Bus (SMIB) demonstrate the effectiveness of the proposed approach.

Sliding mode control for induction machine based on the Lyapunov theory

In this paper, we develop a new control approach for IM. The IM mechanical speed variable perfectly follows its references through a PI controller based on the sliding mode. The associate PI gains of the flux regulator are calculated by pole placement method. The basic idea of this technic is to make stable the closed loop system in the sense of Lyapunov. This method compared with traditional IM control use a simple calculation by the fact that we obtain a global asymptotic stability. The objective of this control technic is based on an appropriate choice of the voltage control values that guaranty a global stability of the closed loop system.

Observation of IM mechanical speed Comparative study of a high gain interconnected observer and an adaptive observer

In the context of a more detailed knowledge of nonlinear observers, we become interested in studying the behavior of the speed error of the induction machines for various function regimes. The aim of this work is the comparison between two types of observers applied to the induction machine to allow the proper selection of the solution. The observers selected are the adaptive observer and the interconnected observer.

A new control technic for induction machine based on the Lyapunov theory

In this paper, we develop a new control approach for IM. The basic idea of this technic is to make stable the closed loop system in the sense of Lyapunov. This method compared with traditional IM control use a simple calculation by the fact that we obtain a global asymptotic stability. The objective of this control technic is based on an appropriate choice of the voltage control values that guaranty a global stability of the closed loop system. The IM mechanical variables perfectly follow their references through two PI controllers. The associate PI gains are calculated by pole placement method.