The generalized magnetizing curve series for the nonlinear magnetic circuit is proposed. Subsequently, three definitions of selfinductance for the nonlinear magnetic circuit are compared. The passivity of the magnetic circuit is reconsidered. Three theorems that describe features of Fourier harmonics of distorted waveforms have been proved.

The article presents selected static characteristics of a parallel active filter with voltage control in the supply line (VPAPF – Voltage-controlled Active Power Filter) as a function of parameters of the supply network. The tests were done on the basis of a simulation model of the supply network and an appropriate compensator. The test results showed that VPAPFs are most suitable for operation in weak networks, maintaining an almost constant level of voltage distortion, regardless of the value of the network impedance. In addition, the influence of the parameter G corresponding to the conductance value suppressing higher harmonics of the network voltage on the operation of the active power filter was determined.