29-05-2012, 01:13 PM
A Novel Control Scheme for a Doubly
A Novel Control Scheme for a Doubly.ppt (Size: 2.63 MB / Downloads: 58)
Wind Generator Topologies
Doubly-fed.
The doubly-fed topology is the most common for high power.
Rotor control allows for speed control of around 25% of synchronous.
Rotor converter rating is only around 25% of total generator rating.
Reactive power control.
Wind Energy Issues
Wind is intermittent
Limits wind’s percentage of the energy mix
Wind energy is often located in rural areas
Rural grids are often weak and unstable, and prone to voltage sags, faults, and unbalances
Unbalanced grid voltages cause many problems for induction generators
Torque pulsations
Reactive power pulsations
Unbalanced currents
Research Objectives
Research was carried out from 2002 to 2005 at the U of M and at NTNU in Trondheim, Norway on a Fulbright scholarship
Doubly-fed induction generators are the machines of choice for large wind turbines
The objective is to develop a control methodology for a DFIG that can achieve:
Variable speed and reactive power control
Compensation of problems caused by an unbalanced grid
Reduce torque pulsations
Reduce reactive power pulsations
Balance stator currents
3 Phase Voltage Unbalance
Causes torque puslations, reactive power pulsations, unbalanced currents, possible over heating
Unbalance can be seen as the addition of a negative sequence
Unbalance factor (VUF, IUF) is the magnitude of the negative sequence over the magnitude of the positive sequence