Compensation of non-periodic currents using the instantaneous power theory

This paper presents a discussion about the use of the instantaneous active and reactive power theory (p-q Theory) for the compensation of non-periodic currents in three-phase circuits. First, the concept behind the term non-periodic is discussed. A summary of the basic points of the instantaneous power theory is presented and them some examples of nonperiodic currents and their identification and compensation by active filters are presented. This paper shows that it is not possible to have at the same time a perfect compensation, where the source currents are purely sinusoidal and the power flowing in the circuit is constant. The user has to decide which condition has higher priority and adapt the compensation characteristics of the active filter.