Development of Induction Machines in Wind Power Technology

Abstract

Abstract-This paper gives an overview of the development of the induction machine as a generator for wind turbines from the middle of the 20th century up to now. After a short history chapter the different energy conversion concepts are presented. At first a squirrel cage machine is direct coupled to the grid (Danish concept). To adjust the machine speed the second step is a wound rotor machine with collector rings to change rotor resistance. This concept allows the first adaption of the operating point of the wind turbine and the induction machine. Another concept is to connect the stator of a squirrel cage machine with a full inline voltage source converter to the grid to get the flexibility in rotational speed and to control the reactive power. The doubly fed induction machine is the latest development. This concept uses a bidirectional voltage source converter in the rotor circuit with a rated power of only 30% of the rated generator power. Now it is possible to change the rotational speed and the reactive power independently and in a wide range. A generalized control scheme of a modern doubly fed induction machine (DFIG) is shown in the last part to explain the variability and the range of application. Today over 70% of the wind turbines are build up with DFIG.

Magnetization of speed sensorless squirrel-cage induction generator for wind power application using a phase-locked loop

“…Despite its exponential growth over the last decade, wind power still has great potential for future development based on ever increasing reliability and ever reducing costs in wind power generation. With the development of power electronics and control technology, the cost per kW of a power converter has lowered and a squirrel-cage induction generator (SCIG) with a full-scale power converter has become an attractive solution in variablespeed wind energy conversion systems (WECSs) [1,2]. Robustness, affordable price and low maintenance requirements as well as costs make the SCIG a prospective choice for wind generation.…”

Rotor flux estimation method for cage induction generators used in wind power applications

“…The SCIG used with full-scale power converter provides reliable and robust solution for variable speed wind energy conversion systems [1], [4], [5]. The high performance control of SCIG based wind turbines is achieved by using the field oriented vector control (FOC) technique.…”

“…FOC is based on the machine flux orientation and provides decoupling of the torque-generating current and the field-generating current. As a result, the performance of vector controlled induction machines is severely influenced by the accuracy of the estimated flux position [5]- [9]. The most popular type of FOC nowadays is rotor field oriented control (RFOC) which is used in this paper.…”

Steady-state analysis and voltage control of Self-Excited Induction Generator (SEIG)

“…In Grid Connected Induction Generator (GCIG) configuration, the generator draws its reactive power from the grid. [3,4,5] have in detailed explained the principal operation of Grid Connected Induction Generator. Another method for providing reactive power required for generator magnetization is by connecting VAR generating units in the form of capacitor banks across its stator terminals.…”