P. Rastgoufard

Bio: P. Rastgoufard is an academic researcher from Tulane University. The author has contributed to research in topics: Kinematics equations & Electric power system. The author has an hindex of 9, co-authored 29 publications receiving 422 citations.

Design, simulation and implementation of three-pole/four-pole topologies for active filters

Abstract: Three-pole/four-pole topologies of current-controlled voltage source inverters (CC-VSI) used as active filter (AF) are considered. The proposed AF system employs power balance theory, which is implemented using a TMS320C31 DSP. A four-pole topology for the AF system exhibits the facility of operating it as a three-pole device. A prototype model of the AF system has been designed and tested with a non-linear load to demonstrate its effectiveness for harmonic elimination, reactive power compensation and power-factor correction. After the control scheme was verified through extensive experimental investigations on a three-pole AF system, it was applied to demonstrate the performance of a four-pole AF system through simulation with different possibilities for the non-linear loads in field applications. Simulation and experimental results of the developed model of the AF system are given and discussed in detail.

An Improved Control Algorithm for Active Filters

Abstract: This paper proposes a new control algorithm resulting in significant advantages toward smooth control of an active filter (AF). The majority of existing feedforward control methods of the AF system result in switching notches (sharp-rising ripples) in the supply current during transitions of stepped waveshaped nonlinear load current. This is due to switching signals for the AF devices, which are obtained by comparison of the sensed and reference currents of the AF. The proposed control algorithm is based on feedback control, wherein, switching signals for the AF devices are obtained by comparing sensed and reference supply currents. This not only eliminates switching notches in the supply currents but also reduces the supply current total demand distortion below the 5% mark recommended by the IEEE-519 standard. A TMS320C31 digital signal processor is used for real-time implementation of the proposed algorithm. To establish its viability and flexibility, the proposed algorithm is also experimented with a laboratory prototype of the AF system made of a reduced number of switches

Line of sight robot navigation toward a moving goal

Abstract: In this paper, we consider the problem of robot tracking and navigation toward a moving goal. The goal's maneuvers are not a priori known to the robot. Thus, off-line strategies are not effective. To model the robot and the goal, we use geometric rules combined with kinematics equations expressed in a polar representation. The intent of the strategy is to keep the robot between a reference point, called the observer, and the goal. We prove under certain assumptions that the robot navigating using this strategy reaches the moving goal successfully. In the presence of obstacles, the method is combined with an obstacle avoidance algorithm. The robot then moves in two modes, the navigation mode and the obstacle avoidance mode. Simulation of various scenarios highlights the efficiency of the method and provides an instructive comparison between the paths obtained for different reference points.

Power system voltage stability and security assessment

Abstract: The purpose of this investigation is to review the recent research progress in voltage stability and security assessment of power systems. This paper presents the fundamental concepts of voltage stability, gives a short recall of the classical voltage theory and different criteria currently available for predicting voltage collapse problems in power systems, which have been associated with multiple power flow solutions, bifurcation, dynamics of tap changers, stochastic loads, singular values, etc. The various methods for studying voltage collapse are compared. The application of expert system techniques to assist in the decision-making process of the reactive power/voltage control problem of power systems and future research directions towards voltage stability and security assessment will also be proposed in this paper.

Multi-robot hunting behavior

Abstract: In this paper we consider the problem of hunting an unpredictably moving prey using a group of robots. We elaborate a mathematical model for the tracking-navigation problem based on geometric rules. This model consists of systems of two differential equations describing the relative motion of the prey with respect to the robots. The control laws are decentralized and the robots move in different modes, namely: navigation-tracking mode, obstacles avoidance mode, cooperative collision avoidance, and circle formation. In the tracking-navigation mode, we use the deviated pursuit strategy, which consists of a closed loop control law based on geometric rules. The properties of this strategy are explored briefly. For obstacles and cooperative collision avoidance, a collision cone approach is used. Our method is illustrated using simulation.

Correction to “Experimental Design of a Nonlinear Control Technique for Three-Phase Shunt Active Power Filter”

Abstract: This paper presents a nonlinear control technique for a three-phase shunt active power filter (SAPF). The method provides compensation for reactive, unbalanced, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently nonlinear SAPF system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the SAPF output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that significantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the SAPF reference currents, is proposed. The first step is to extract the SAPF reference currents from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase diode bridge rectifier with R-L load is taken as the nonlinear load, and then, the reference currents are modified, so that the delay will be compensated. The converter, which is controlled by the described control strategy, guarantees balanced overall supply currents, unity displacement power factor, and reduced harmonic load currents in the common coupling point. Various simulation and experimental results demonstrate the high performance of the nonlinear controller.

Wolf-pack (Canis lupus) hunting strategies emerge from simple rules in computational simulations

Abstract: We have produced computational simulations of multi-agent systems in which wolf agents chase prey agents. We show that two simple decentralized rules controlling the movement of each wolf are enough to reproduce the main features of the wolf-pack hunting behavior: tracking the prey, carrying out the pursuit, and encircling the prey until it stops moving. The rules are (1) move towards the prey until a minimum safe distance to the prey is reached, and (2) when close enough to the prey, move away from the other wolves that are close to the safe distance to the prey. The hunting agents are autonomous, interchangeable and indistinguishable; the only information each agent needs is the position of the other agents. Our results suggest that wolf-pack hunting is an emergent collective behavior which does not necessarily rely on the presence of effective communication between the individuals participating in the hunt, and that no hierarchy is needed in the group to achieve the task properly.

An Advanced Current Control Strategy for Three-Phase Shunt Active Power Filters

Abstract: This paper proposes an advanced control strategy to enhance performance of shunt active power filter (APF). The proposed control scheme requires only two current sensors at the supply side and does not need a harmonic detector. In order to make the supply currents sinusoidal, an effective harmonic compensation method is developed with the aid of a conventional proportional-integral (PI) and vector PI controllers. The absence of the harmonic detector not only simplifies the control scheme but also significantly improves the accuracy of the APF, since the control performance is no longer affected by the performance of the harmonic tracking process. Furthermore, the total cost to implement the proposed APF becomes lower, owing to the minimized current sensors and the use of a four-switch three-phase inverter. Despite the simplified hardware, the performance of the APF is improved significantly compared to the traditional control scheme, thanks to the effectiveness of the proposed compensation scheme. The proposed control scheme is theoretically analyzed, and a 1.5-kVA APF is built in the laboratory to validate the feasibility of the proposed control strategy.

Technique for online prediction of voltage collapse

Abstract: A new technique for predicting voltage collapse in power systems in an online mode is described. This technique uses the voltage magnitude and voltage angle information at buses and the network admittance matrix to predict voltage collapse. The performance of the technique was studied for a variety of operating conditions. The technique was tested using different IEEE test systems. The simulations were carried out for steady-state voltage collapses and for dynamic voltage collapses. The results indicate that, for every bus in the system, the proposed technique can predict its proximity to voltage collapse by means of an index. This method is computationally efficient and suitable for real time prediction of voltage collapse. An online implementation of the technique using UCA is also proposed.

A T-Connected Transformer and Three-leg VSC Based DSTATCOM for Power Quality Improvement

Abstract: In this paper, a new three-phase four-wire distribution static compensator (DSTATCOM) based on a T-connected transformer and a three-leg voltage source converter (VSC) is proposed for power quality improvement. The T-connected transformer connection mitigates the neutral current and the three-leg VSC compensates harmonic current, reactive power, and balances the load. Two single-phase transformers are connected in T-configuration for interfacing to a three-phase four-wire power distribution system and the required rating of the VSC is reduced. The insulated gate bipolar transistor (IGBT) based VSC is supported by a capacitor and is controlled for the required compensation of the load current. The DC bus voltage of the VSC is regulated during varying load conditions. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination, and balancing of linear loads as well as nonlinear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and power system blockset toolboxes.