Adel Shaltout

Reclosing torques of large induction motors with stator trapped flux

Large induction motors are subjected to high transient torques following the rapid reconnection of the supply. The paper shows that these torques have oscillatory components with speed dependent frequencies. These components may result in high torsional torques if the supply is reconnected at an unfavorable instant; when the frequency of one of the torque components coincides with the natural torsional frequency. However, this high torque can be avoided by the proper choice of the reclosing instant.

An Unsymmetrical Two-Phase Induction Motor Drive With Slip-Frequency Control

This paper proposes a closed-loop control strategy to operate an off-the-shelf single-phase induction motor (IM) as a symmetrical two-phase IM. The proposed control strategy employs the SFC technique to independently control the stator currents of both the main and auxiliary windings, and make them follow a predefined sinusoidal waveform. Simulation and experimental results show that the proposed scheme is successful in operating the conventional single-phase IM as a symmetrical two-phase IM with fast dynamic and transient responses. In addition, the proposed control system achieves cost-effectiveness in both initial and running costs.

Fault Tolerant Field Oriented Control of the Induction Motor for Loss of One Inverter Phase

This paper presents a fault tolerant strategy for the problem of loss of one phase in a field oriented controlled three phase induction motor. The proposed solution, rather than previously suggested solutions, is a control strategy in the single phase mode of operation of the induction motor. The suggested strategy can be applied to both delta and star connected motors. Average torque equivalent to the required reference torque is obtained. Tests are applied experimentally on a 10 kW motor to validate the proposed strategy. Limitation due to maximum permissible current is also discussed

A novel double-circuit-rotor balanced induction motor for improved slip-energy recovery drive performance. II. Experimental verification and harmonic analysis

The merits of the new slip-energy recovery drive system that has been proposed in Part I of this paper (see ibid., vol.11, no.3, p.556-62, 1996) is demonstrated here. Experimental work is carried out to verify the simulated, models of the proposed and conventional systems. Furthermore, harmonic analysis of both systems is conducted analytically and confirmed numerically using the FFT. The main feature of the new proposed system is the significant reduction in the harmonics of the rotor flux linkage. This leads to substantial reductions in the stator current harmonics. Moreover, the pulsating components in the developed electromagnetic torque are also reduced significantly in the new proposed system.

Optimum sizing of hybrid WT/PV systems via open-space particle swarm optimization

Renewable energy resources, such as wind turbines (WT) and photovoltaic cells (PV), can serve as an alternative to fossil fuel-generated electricity. They are being considered as the most promising new energy sources due to their availability and topological advantages in local power generation, but they have a drawback in that electrical output energy is unstable besides the initial and maintenance costs are expensive. This paper presents a novel technique to extract the optimum sizing of hybrid renewable energy generation system (HRES) with storage system via open space particle swarm optimization (OSPSO). The simulation using this technique is shown. The total system cost is the objective function. The technical sizing is a constraint.

Fault Tolerant Field Oriented Control of Induction Motor for Loss of One Inverter Phase with Re-starting Capability

This paper describes a novel strategy for restarting the three phase induction motor in a voltage fed field oriented drive operating in the single phase mode after the loss of one of the inverter phases. The proposed method makes use of the readily presented switches for isolating the machine phase corresponding to the faulty inverter leg in the fault tolerant induction motor drive. With the aid of the two healthy inverter phases, three phases of the machine and sequential switching of two switches, block currents are fed into the machine to produce net average positive torque capable of restarting the machine. After the machine reaches a suitable speed the control structure is changed to the single phase field orientated mode of operation. The strategy is verified by computer simulation on a 10 kW induction machine.

Analysis and Design of Photovoltaic Powered Air Conditioners Using Slip-frequency Control Scheme

Abstract This article proposes a new scheme to drive an air conditioner powered by photovoltaic (PV) arrays. The main objective is to reduce the cost of the system, which is a major concern in PV applications. This is achieved by reducing both the initial and running costs of the PV system. Initial cost is cut down by reducing the required size of the PV array through (i) limiting the motor current during both startup and dynamic phases of operation, and (ii) extracting maximum power from the PV array under various metrological conditions by operating the PV array on the maximum power line. Reduction in the running cost of the PV system is achieved by controlling the motor speed such that its slip is kept at a small value at various operating conditions, ensuring highly efficient operation of the system. This article outlines a procedure for sizing the photovoltaic array. Also, the article presents a control strategy that achieves acceptable levels of the motor current with good dynamic response. Simulation results of the system behavior during transient and dynamic phases confirm the capability of the proposed scheme.

Polynomial computational method tracking MPP using enhanced PV diode model

This paper presents a simple computational method for engineers and researchers seeking maximum power points under different climatic conditions. This computational method has been proposed by the polynomial generic equation for electrical parameters related to maximum power points (MPPs), which are named respectively; power, voltage, and current values. This method has been applied to specific photovoltaic mono-crystalline type named shell SP-70. In this regard, an accurate modeling of PV is highly required to track MPPs. The shell SP-70 has been modeled in the ideal case study. In addition, a practical case by using an enhanced PV diode model (EPVDM) that has been brought out through an algorithm with more enhancements for the extraction of solar module parameters. The parameters obtained by this EPVDM have been verified with experimental results and other model types presented by others. Detailed studies have been carried out for a polynomial computational method (PCM) which is based on two stages; built-up matrix data about PV SP-70 at ideal and practical cases. Then, curve fitting technique has been applied to generate mathematical equations of PCM in third and fifth orders.

Slip-frequency control of single-phase induction motor operated as two-phase motor

This paper proposes a closed-loop control strategy to operate an off-the-shelf single-phase induction motor (I.M.) as an unsymmetrical two-phase motor. The proposed control strategy employs the slip frequency control technique to independently control the stator currents of both main and auxiliary windings and make them follow a predefined sinusoidal wave. Simulation results show that the proposed scheme is successful in operating the single-phase induction motor as an unsymmetrical two-phase motor with fast dynamic and transient responses. Notably, the proposed control scheme achieves reduction in the inherent torque oscillations of the two-phase unsymmetrical I.M, rendering its behavior similar to its symmetrical counterpart. In addition, the proposed control system achieves cost-effectiveness in both initial and running costs. Thus, the proposed work presents a novel cost-effective control and application of the single-phase induction motor.

A novel double-circuit-rotor balanced induction motor for improved slip-energy recovery drive performance. I. Modeling and simulation

A new construction for the rotor windings of balanced wound-rotor induction motors employed in the slip energy recovery drives is proposed, in this paper, to reduce the time harmonics which are commonly generated in the machine. The proposed machine has a double-circuit in the rotor. One circuit is star connected while the other is delta connected. Each of these two circuits is connected to a diode-bridge rectifier to achieve a twelve-pulse operation characteristics. The main objective of this paper is to develop a new model which is capable of simulating the proposed machine, neglecting nonlinearities due to magnetic saturation, and its associated converters. Such a model is further complicated due to the presence of the two rotor circuits and their mutual interaction.