Modeling and Modern Control of Wind Power

Chapter 3Control of Doubly-fed Induction Generators for Wind Turbines

Guojie Li¹ and Lijun Hang²

¹Department of Electrical Engineering, Shanghai Jiaotong University, China

²Hangzhou Dianzi University, Hangzhou, China

3.1 Introduction

The doubly-fed introduction generator (DFIG) has a growing market. The term “doubly-fed” refers to the fact that the voltage on the stator is applied from the grid and the voltage on the rotor is induced by the power converter. It also means there is both stator- and rotor-fed power to the grid. This system allows a variable-speed operation over a large but restricted range (±30% of synchronous speed). The converter compensates for the difference between the mechanical and electrical frequency by injecting a rotor current with a variable frequency. Both during normal operation and faults, the behavior of the generator is thus governed by the power converter and its controllers [1, 2].

This chapter is arranged as follows. The principles of DFIGs are introduced in Section 3.2. PQ control and direct torque control of DFIGs is presented in Sections 3.3 and 3.4, respectively. Low-voltage ride through of the DFIG is described in Section 3.5. In Section 3.6, conclusions are drawn.

3.2 Principles of Doubly-fed Induction Generator

Doubly-fed induction generator (DFIG) technology is widely used in wind turbine applications. This is mainly because the power electronic converter only has to handle a fraction (20–30%) of the total power and therefore is cheaper. ...