A New Control Scheme for Load Side Converter of Stand-Alone Doubly Fed Induction Generator

Abstract

In this paper, a simple and novel control strategy for a stand-alone doubly fed induction generator (DFIG)-based wind turbine under combined unbalanced and non-linear loads is presented. These types of loads cause negative sequence and harmonics in the stator voltage and current, which leads to power and torque oscillation. As a solution, a new control strategy is presented in the load side converter (LSC) which compensates for the stator current and voltage, simultaneously. The instantaneous active and reactive power theory is used to extract all of the harmonic components of the stator current and voltage. Based on the presented papers, the main task of LSC is to compensate for the stator current. In our proposed method, the per-unit values of stator voltage harmonics are added to the LSC's reference signals. Because the resulted reference signals are sinusoidal, the proportional-resonant (PR) controller is used to track the sinusoidal references. Therefore, the stator voltage is compensated in addition to the stator current for all types of loads, and the rotor side converter is only required to control the voltage amplitude and frequency. The harmonic components are extracted by algebraic equations. So, the system has a fast dynamic response, which is suitable for practical implementation. To validate the presented control strategy, simulation and experimental implementation for a 5.5 kW DFIG are done in the paper.