A new concept in evaluating power system distortions under unbalanced and nonsinusoidal conditions

This paper presents a new index to evaluate a distorted signal under unbalanced and harmonic conditions. This criterion is called total harmonic and unbalanced distortion (THUD) which can be used to calculate the amount of harmonics and unbalance of voltage, current and power waveforms. Whereas conventional factors such as V/V + and THD are fairly incomplete to express the total distortion of a signal in both harmonic and unbalanced environments, the use of alternative factors in such cases seems to be mandatory. It is demonstrated that the proposed voltage total harmonic and unbalanced distortion (VTHUD) along with voltage total harmonic distortion (VTHD) and voltage total unbalanced distortion (VTUD) are appropriate factors to achieve to this purpose. Furthermore, THUD is an extensive factor to compare two distorted environments from aspect of power quality issues.