Abstract: In this paper generalized definition of instantaneous power quantity in the multiphase system under unbalanced and non-sinusoidal supply condition is discussed. In the area of Active Power Line Conditioners (APLC), shunt APLC is widely used in practice. Many reference current generation methods are proposed by different researchers, but most of them work optimally with balanced and sinusoidal source voltage. This paper proposes a novel concept of decomposing the multiphase current vector into different components, which represents different component of the power quantity. The formation of calculating compensation current according Generalised Instantaneous Power Theory (GIPT) and Modified GIPT has been studied. Next, the behavior of a shunt APLC with these two theories has been studied. Performance of shunt APLC tested and compared under unbalanced non-sinusoidal supply condition. Under distorted and/or unbalanced system voltages, GIPT does not compensate properly the load currents and injects harmonic currents into the supply, which are not originated from the non linear load. Necessary modifications in GIPT more general compensation objective is possible.The validity of the proposed control scheme is verified by the simulation study.

Keywords: Active filters, instantaneous power, geometric algebra, nonsinusoidal waveforms, power multivector.