International Journal of Engineering Research

Mahmoud A. Saleh ¹, Maged N. F. Nashed ¹, Mona N. Eskander ¹

Affiliations
1 Electronics Research Institute, Cairo, EG

Abstract

In this paper an integrated system of WECS, battery storage and controller is proposed to supply electrical energy to a small community in a remote area in Egypt. The layout and the configuration are presented and discussed. Also, a new wind speed frequency distribution model is proposed based on the prevailing wind speed in this area. The validity of the model is tested for different sites in Egypt. The model and the relevant equation express the wind speed frequency distribution in terms of the prevailing wind speed in the site and it frequency distribution, hence it can be applied for any site all-over the world with known wind speed profile. Based on this model, the size and rated speed of the WECS to provide electrical energy to the specified loads in this remote area can be determined.

Keywords

WECS, DFIG, Bi-Directional Converter, and Micro-Grid.

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Maged N. F. Nashed ¹, Mona N. Eskander ¹, Mahmoud A. Saleh ¹

Affiliations
1 Electronics Research Institute, Cairo, EG

Abstract

In this paper the dynamic performance of a stand-alone wind-driven Single Machine-Brushless Double Fed Generator (SM-BDFIG), supplying different loads in remote area is investigated. The battery embedded in the frame of the specially designed SM-BDFIG is used for energy storage in the super synchronous range of operation. The stored energy is used to supply enough slip power for the rotor circuit of the generator in the sub-synchronous range of operation, to feed the rotor with the necessary DC power at synchronous speed, and also to supply the priority loads at low wind speeds equal or below the cut-in speed. A programmable logic controller (PLC) is designed to control the operation of the rotor converters according to the wind speed and to manage the whole stand-alone system. The dynamic performance of the generator at variable wind speeds is studied. The effect of varying loads on the generator currents, voltages, and electromagnetic torque are given for variable wind speeds. Also the effect of sudden change in the wind speed on the SM-BDFIG performance is investigated. The investigation is done at synchronous speed as well as sub-synchronous and super-synchronous speeds. Results proved the stable operation of the proposed machine as generator at within the whole speed range (from sub-synchronous speed to super-synchronous) stably.

Keywords

Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG", 3-Phase Bridge Rectifier, Super-Synchronous Operation, Battery Charge, and DC Link.

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Mahmoud A. Saleh ¹, Mona N. Eskander ¹, Maged N. F. Nashed ¹

Affiliations
1 Electronics Research Institute, Cairo, EG

Abstract

In this paper the sub-harmonics associated with a specially designed single machine brushless doubly fed induction generator (SM-BDFIG) are analyzed at super synchronous speeds. The SM-BDFIG is coupled to a variable speed wind turbine, and its rotor circuit is connected to a 3-phase rectifier feeding Li-ion batteries. A mathematical model, using Fourier expansion, is developed to define the sub harmonics created by the time harmonics of the rotor currents irrespective of any other space or time harmonics due to winding distribution, unbalanced grid phases, or presence of harmonics in the grid voltages. The effect of the positive and negative sequence harmonics on the performance of the generator is then presented, showing the speed ranges within which these sub-harmonics are most effective, as well as the speed ranges within which these sub-harmonics are least effective. The obtained results help to design a SM-BDFIG with less harmonic distortion, hence improving its performance in wind energy conversion systems.

Keywords

Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG", 3-Phase Bridge Converter, Subharmonics, Battery Charge, and DC Link.

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Mahmoud A. Saleh ¹, Maged N. F. Nashed ¹, Mona N. Eskander ¹

Affiliations
1 Electronics Research Institute, Cairo, EG

Abstract

In this paper a simplified mathematical model of a single machine brushless double fed induction generator (SM-BDFIG) connected to a variable speed wind turbine is presented. The SM-BDFIG consists of a slip ring induction machine, which is the main generator, a converter, and a battery pack mounted on the same shaft. In the super-synchronous speed range of operation, which is investigated in this research paper, the rotor voltage is rectified and used to charge the batteries. The steady state performance of the proposed generator is studied at different values of battery open circuit voltage, different values of the battery internal resistance, and different ratios of rotor leakage reactance to rotor resistance. Results revealed that the parameter that had a significant effect on the machine performance is the ratio of rotor leakage reactance to rotor resistance.

Keywords

Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG", 3-Phase Bridge Converter, Super-Synchronous Operation, Battery Charge, and DC Link.

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Mona N. Eskander ¹, Mahmoud A. Saleh ¹, Maged N. F. Nashed ¹

Affiliations
1 Electronics Research Institute, Cairo, EG

Abstract

In this paper, the dynamic performance of the specially-designed Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG" coupled to variable speed wind turbine is investigated. The rotor voltage of the SM-BDFIG during super-synchronous operation is used to charge a number of batteries, connected to the rotor via a 3- phase bridge rectifier. The number of charged battery cells are changed, by parallel and series connections, according to the wind speed variation, and consequently, the rotor voltage variation. The response of the stator, rotor, and DC link voltages and currents due to wind speed variations is presented. The electromagnetic torque, the stator active power, and the rotor active power during wind speed variations are also presented.

Keywords

Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG", 3-Phase Bridge Rectifier, super-Synchronous Operation, Battery Charge, and DC Link.

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