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Title: Dynamic analysis of a doubly fed generator in power system applications

Abstract

In this paper, the dynamic performance and control of a doubly fed generator is investigated. It is shown experimentally that a reactive current regulator can be used to control the machine excitation level. The study initially assumes an externally controlled field frequency, so that the machine is in the controlled speed mode. Linearized analysis is used to show that larger generators may be subject to dynamic instabilities at high slip operation. It is shown that feedback of shaft speed along with the stator or rotor current vector can be used to provide stable operation.

Authors:
 [1];  [2]
  1. (EMD Dept., Univ. of Aleppo, P.O. Box 7680, Aleppo (Syrian Arab Republic))
  2. (Electrical and Computer Engineering Dept., Clarkson Univ., Potsdam, NY (United States))
Publication Date:
OSTI Identifier:
7022276
Alternate Identifier(s):
OSTI ID: 7022276
Resource Type:
Journal Article
Resource Relation:
Journal Name: Electric Machines and Power System; (United States); Journal Volume: 20:5
Country of Publication:
United States
Language:
English
Subject:
24 POWER TRANSMISSION AND DISTRIBUTION; ELECTRIC GENERATORS; DESIGN; PERFORMANCE TESTING; POWER SYSTEMS; OPERATION; PLANNING; CONTROL EQUIPMENT; VOLTAGE REGULATORS; EQUIPMENT; TESTING 240100* -- Power Systems-- (1990-)

Citation Formats

Rifai, M.B., and Ortmeyer, T.H. Dynamic analysis of a doubly fed generator in power system applications. United States: N. p., 1992. Web.
Rifai, M.B., & Ortmeyer, T.H. Dynamic analysis of a doubly fed generator in power system applications. United States.
Rifai, M.B., and Ortmeyer, T.H. Wed . "Dynamic analysis of a doubly fed generator in power system applications". United States. doi:.
@article{osti_7022276,
title = {Dynamic analysis of a doubly fed generator in power system applications},
author = {Rifai, M.B. and Ortmeyer, T.H.},
abstractNote = {In this paper, the dynamic performance and control of a doubly fed generator is investigated. It is shown experimentally that a reactive current regulator can be used to control the machine excitation level. The study initially assumes an externally controlled field frequency, so that the machine is in the controlled speed mode. Linearized analysis is used to show that larger generators may be subject to dynamic instabilities at high slip operation. It is shown that feedback of shaft speed along with the stator or rotor current vector can be used to provide stable operation.},
doi = {},
journal = {Electric Machines and Power System; (United States)},
number = ,
volume = 20:5,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1992},
month = {Wed Jan 01 00:00:00 EST 1992}
}
  • In this paper, the dynamic performance and control of a doubly fed generator is investigated. It is shown experimentally that a reactive current regulator can be used to control the machine excitation level. The study initially assumes an externally controlled field frequency, so that the machine is in the controlled speed mode. Linearized analysis is used to show that larger generators may be subject to dynamic instabilities at high slip operation. It is shown that feedback of shaft speed along with the stator or rotor current vector can be used to provide stable operation.
  • Operating characteristics of a doubly fed generator, driven by a variable speed prime mover and excited by a cycloconverter, are studied. It is assumed that the generator is connected to a constant frequency power system. Analysis is conducted on a linearized model of the generating system and its eigenvalue structure is used to study the system stability against the disturbances. A computer simulation on the nonlinear model is presented to confirm the validity of the linearized model analysis and to show the dynamic response for large disturbances. An experimental system was built and tested in the laboratory to verify themore » analytical study. The doubly fed machine model and the cycloconverter model are converted to the synchronously rotating d and q axes to make the system suitable for linearization. The system model consists of a set of nonlinear differential equations written in state space form. The linearized model is obtained by applying the small displacement theory on the nonlinear model using typical data for a wound rotor machine. The effect of system parameters variation on stability was investigated. It was shown that the possibility of instability exists in the system. The ability of state feedback to stabilize the system and improve the dynamic response was studied. The computer simulation results are in agreement with the results predicted from the eigenvalue study.« less
  • If a large disturbance occurs in a power grid, two auxiliary loops for the inertial control of a wind turbine generator have been used: droop loop and rate of change of frequency (ROCOF) loop. Because their gains are fixed, difficulties arise in determining them suitable for all grid and wind conditions. This paper proposes a dynamic droop-based inertial control scheme of a doubly-fed induction generator (DFIG). The scheme aims to improve the frequency nadir (FN) and ensure stable operation of a DFIG. To achieve the first goal, the scheme uses a droop loop, but it dynamically changes its gain basedmore » on the ROCOF to release a large amount of kinetic energy during the initial stage of a disturbance. To do this, a shaping function that relates the droop to the ROCOF is used. To achieve the second goal, different shaping functions, which depend on rotor speeds, are used to give a large contribution in high wind conditions and prevent over-deceleration in low wind conditions during inertial control. The performance of the proposed scheme was investigated under various wind conditions using an EMTP-RV simulator. The results indicate that the scheme improves the FN and ensures stable operation of a DFIG.« less