A new method for voltage quality evaluation based on p-q-r theory

Many PQ standards have been established according to single PQ problem, which cut off the relations among different PQ problems. Furthermore, this kind of standards for single PQ problem has no good for the evaluation of customer´s losses and the effect of PQ deterioration on electricity price. New definition of distorted powers and their distorted factors to evaluate voltage quality is defined based on p-q-r theory. Then a relative distorted factor f_rd and an absolute distorted factor f_ad are proposed in this paper. In both of the two factors, voltage quality problems such as voltage deviation, three-phase voltage unbalance, harmonics, etc. are considered. In the relative distorted factor, different load sensitivity and load characteristic of customers are considered too. For the same PQ problem, different customer will have different relative distorted factor. While the absolute distorted factor reflect the severity of voltage quality at PCC objectively. Simulation results clearly show that the voltage at PCC can be evaluated synthetically through the two factors from the energy angle.