Effects of the Load Harmonics Variation on the Performance of Shunt Active Filters

This paper presents the study of such shunt active filters which inject compensating current into the network with delay of one or two periods of network frequency. It is shown that the performance of the filter is influenced by the variation of the nonlinear load harmonic contents. Practical data is obtained from several industrial and domestic loads. The samples of the load currents are analyzed using FFT algorithm. The delay in the compensating current injection is simulated by matlab software and harmonics of the source current after compensation are compared with the standard permitted harmonic levels (IEEE 519). It is seen that the compensation is not completed for nonlinear loads and, in some cases, did not satisfy the standard requirements. Thus, it is concluded that before selecting a control strategy for the active filter (moreover, before selecting an active filter for compensation), behavior of the nonlinear loads must be studied and inspected from harmonic content variation point of view