Harmonics Reduction and Reactive Power Injection in Wind Generation Systems

Abstract

In this work, methods are implemented to improve two aspects of energy quality in a wind generation system. First, the harmonic reduction is achieved by applying a linear control technique in the Grid Side Converter; and second, the power factor of the wind generation system using a Doubly Fed Induction Generator (DFIG) is adjusted by injecting reactive power. The reduction of the harmonic content is performed with a digital resonant controller, which tracks the periodic signals corresponding to the current harmonics of the Grid Side Converter (GSC), which is part of a “back to back” converter in a wind generation system. This technique allows implementing a current controller of the GSC with a high level of rejection of current harmonics, of frequencies with orders (1 + 6k) and (1 − 6k) (where k is an integer), when executed in the synchronous reference frame (dq). The purpose of this work is to inject currents to the grid with very low harmonic distortion and provide a method for tuning the resonant controller for a simple L filter; also, the GSC is used to generate reactive power. These two improvements achieve a unity power factor, and this is necessary to comply with the new codes where a leading power factor helps regulate the grid voltage.

Method for the Analysis of Three-Phase Networks Containing Nonlinear Circuit Elements in View of an Efficient Power Flow Computation

“…Nonlinear circuit elements are an important source of harmonics in three-phase networks. Harmonics affect power quality and generate additional losses and overloads, may inflict operation malfunction, and finally significantly decrease the equipment's life cycle or even cause its failure [1][2][3][4][5][6][7][8][9]. The current trend, both in the European Union and worldwide, is to reduce costs and increase the energy efficiency of both industrial and household equipment through the widespread use of power electronics [10][11][12][13].…”