Doctoral Dissertations


HongTao Ma


"This dissertation focuses on wind farm frequency regulation capability to maintain the grid frequency stability. Wind plant power controllers are designed and tested for participation in grid frequency restoration. The small signal stability on sub-optimal operating points is analyzed and a de-loaded operating point is proposed.

In the first paper, a new frequency regulation scheme is developed for the wind turbine/generator/converter trio that will provide the capability to participate in restoring frequency in a way similar to the droop response of conventional generators. Output active power adjustment can be realized by both converter and pitch angle control in addition to inertial response of the wind turbine. This helps in maintaining instantaneous power balance as well as in longer term frequency regulation.

In the second paper, Inertia controller, pitch angle controller and rotor speed controller are introduced for wind plant output active power adjustment. The control schemes are developed for wind generators to equip them with the capability to participate in restoring gird frequency. With the proposed controllers, the wind plant can operate as a synchronous generator and is able to output larger or smaller amounts of power as required so as to contribute to grid frequency restoration. The controllers are tested on a wind plant operating in a 4-bus test system for verification of the grid frequency performance under various system dynamic conditions.

In the third paper, a reduced-3rd order doubly fed induction generator (DFIG) wind turbine dynamic model is described in details. This model along with an active power controller integrated with a power system is investigated for small signal dynamic stability for both sub- and super-synchronous operating conditions. Assuming constant wind speed and blade pitch angle the mechanical power of the machine is modeled as a function of the rotor speed. The system is initialized and linearized around the sub- and super-synchronous operating points. The eigenvalues and participation factors are calculated for a constant power reference as well as 90% P max reference. Both the open loop and closed loop controls on DFIG active power are applied for eigenvalue calculation. The results show that the DFIG operating at the sub-synchronous operating points is unstable"--Abstract, page iv.


Chowdhury, Badrul H.

Committee Member(s)

Kimball, Jonathan W.
McMillin, Bruce M.
Ferdowsi, Mehdi
Crow, Mariesa


Electrical and Computer Engineering

Degree Name

Ph. D. in Electrical Engineering


Missouri University of Science and Technology

Publication Date

Fall 2008

Journal article titles appearing in thesis/dissertation

  • Frequency regulation with wind power plants
  • Working toward frequency regulation with wind power plants: three control approaches
  • Small signal stability analysis of doubly fed induction generator for wind power productio


ix, 66 pages

Note about bibliography

Includes bibliographical references.


© 2008 HongTao Ma, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type




Subject Headings

Electric power system stability
Induction generators -- Design
Wind turbines -- Equipment and supplies

Thesis Number

T 9793

Print OCLC #


Electronic OCLC #


Link to Catalog Record

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