Synchronous generator and frequency converter in wind turbine applications : system design and efficiency

• This report deals with an electrical system for variable-speed wind powerplants. It consists of a synchronous generator, a diode rectifier and athyristor inverter. The aim is to discuss the system design and control, tomodel the losses and to compare the average efficiency of this variable-speedsystem with the average efficiency of a constant-speed and a two-speedsystem. Only the steady state operation of the system is discussed. Losses inthe system are modelled, and the loss model is verified for a 50 kVAgenerator. The proposed simple loss model is found to be accurate enough tobe used for the torque control of a wind turbine generator system. The mostefficient generator rating is discussed, and it is shown how the voltage controlof the generator can be used to maximize the generator and converterefficiency. The average efficiency of the system is calculated. It depends onthe median wind speed of the turbine site. It is found that a variable-speedsystem, consisting of a generator and a converter, can have an averageefficiency almost as high as a constant-speed or a two-speed system. Threedifferent control strategies and their effect on the system efficiency areinvestigated.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

synchronous generator

frequency converter

wind turbine

avrage efficiency

losses

system design

variable speed

Publication and Content Type

lic (subject category)

vet (subject category)