The instantaneous reactive power（IRP）theory advanced by Hirofumi Akagi and the currentsphysical components（CPC）theory advanced by Czarnecki are elaborated，and their relations based on the sinusoidal and non-sinusoidal three-phase three-wire circuit are preliminarily discussed.The results show that the current components and power components as defined have a certain correspondence relationship under the condition of sinusoidal voltage，and each of them is related to a physical phenomenon.However，when the voltage is non-sinusoidal，the relationship between them is by no means clear.The oscillating component of the IRP theory is related to multiple physical phenomena，while there is a definite correspondence between power quantities and physical phenomena in the CPC theory.Finally，their applications in power quality analysis and control are compared by PSCAD simulation.