An improved detecting approach of harmonic current in single-phase active power filter based on tracking differentiator

Extended two-dimensional single-phase harmonic detection algorithm is an approach detecting the harmonic current in single-phase active power filter. However, it is not practical for some reason. In this paper, the algorithm was studied and then an improvement based on tracking differentiator (TD) was proposed to solve the problems existing in the extended two-dimensional single-phase harmonic detection algorithm, in which the magnitude of fundamental wave can be easily affected by high frequency noises of the input signal for the existence of derivation process. The new algorithm is capable of filtering perturbations and getting the derivative of input signal without noise amplification. It can make sure that a more accurate approximation of the real fundamental wave without distortion will be obtained, which can guarantee a lower harmonic content of the grid side current.