HARMONICS AND HOW THEY RELATE TO （谐波,以及它们是如何联系的）.pdf

Proc. of the EPRI Power Quality Issues Opportunities Conference (PQA’93), San Diego, CA, November 1993. HARMONICS AND HOW THEY RELATE TO POWER FACTOR W. Mack Grady The University of Texas at Austin Austin, Texas 78712 Robert J. Gilleskie San Diego Gas Electric San Diego, California 92123 Abstract We are all familiar with power factor, but are we using it to its true potential? In this paper we investigate the effect of harmonics on power factor and show through examples why it is important to use true power factor, rather than the conventional 50/60 Hz displacement power factor, when describing nonlinear loads. Introduction Voltage and current harmonics produced by nonlinear loads increase power losses and, therefore, have a negative impact on electric utility distribution systems and components. While the exact relationship between harmonics and losses is very complex and difficult to generalize, the well- established concept of power factor does provide some measure of the relationship, and it is useful when comparing the relative impacts of nonlinear loads–providing that harmonics are incorporated into the power factor definition. Power Factor in Sinusoidal Situations The concept of power factor originated from the need to quantify how efficiently a load utilizes the current that it draws from an AC power system. Consider, for example, the ideal sinusoidal situation shown in Figure 1. R Irms +