A new experimental method to desegregate the harmonic power produced by thyristor AC/DC three phase converters

摘要

This paper introduces a new experimental method that desegregates the harmonic power in the AC coupling point of thyristor pulse controlled AC/DC three phase power converters, during the occurrence of voltage unbalances in the AC source that feeds the converter. This method of measurement resolves the total harmonic power into two orthogonal harmonic components, whose existence is theoretically demonstrated for sinusoidal voltage and nonsinusoidal current conditions. A scaled down AC/DC/AC transmission link physical model that includes characteristic harmonics passive filtering, and AC primary side weakening facilities is used for measurement purposes. Balanced and unbalanced voltage conditions are also readily simulated in this physical model. The two 3-phase converters linked by a lumped parameters transmission line that constitute the AC/DC/AC system can act either as rectifier or inverter, depending upon the firing angle control imposed on the converter's valves. The two orthogonal harmonic components, that were given by the authors the names of characteristic harmonic power and noncharacteristic harmonic power, have not been previously desegregated neither theoretically nor experimentally. The relevance of this paper may be better judged in the framework of research efforts that have been undertaken to overcome the harmonic content of a noncharacteristic nature. These kind of harmonic effects are present during the steady state that follows an asymmetrical AC disturbance in the coupling point of AC/DC three phase power converters. The paper includes extensive results on such phenomena.