Experimental Evaluation of Wind Turbines Inverters on Generating Harmonic Currents

Abstract

Abstract The search for alternative sources of energy, aimed at supplying the energy matrix, has shown a rapid increase in the use of wind energy worldwide. However, the interaction between wind farms and the electrical networks has shown itself to be an area of research interest. Among those phenomena that require evaluations by regulatory agencies, which in general aim at authorizing access to electric networks, emphasis is given to the following performance magnitudes: harmonic distortions, flicker, impacts on steady state voltages, transitory and dynamic performances, etc. The focus is here placed upon studies related to the estimation of individual and total harmonic distortions that are produced on the connection bus, these are frequently performed through use of computational resources. To this end, the studies are conducted on the basis of injecting individual harmonic current components produced by the generating units, which once adequately fixed, interact with the harmonic impedances determined by the composition of the internal network of the windfarm, along with the geometric locations that characterize the harmonic impedances of the connecting network. Therefore, such evaluations are performed based on equivalent Norton harmonics, which require, as a premise, the harmonic currents that are produced and injected. In this context, the present article is centered on specific issues linked to the qualitative and quantitative characterization of these harmonic currents, with emphasis on operational factors that exert influence on its orders and amplitudes. This work is conducted in order to clarify the origin and nature of the generated currents, the factors that influence such magnitudes, and finally, an evaluation of the theme through experimental studies performed for a laboratory installation aimed at emulating a full converter type of wind generator.