The presence of nonlinear and unbalance loads in a three-phase network causes harmonics generation and dissipation in power network. One of the usual methods used for decreasing and eliminating these effects is the application of active and passive filter. The passive f More
The presence of nonlinear and unbalance loads in a three-phase network causes harmonics generation and dissipation in power network. One of the usual methods used for decreasing and eliminating these effects is the application of active and passive filter. The passive filter is designed for a particular kind of frequency and therefore eliminates a particular harmonics. Its weakness, however, is the possibility of its resonance with the equivalent network impedance and the large size of its elements. The active filter helps to remove the above problems. Moreover, this filter causes the harmonics to be rejected individually or all together and prohibits the occurrence of resonance with the network. One of the problems of these filters is the limited dynamics response that considers the steady state of harmonics. In this paper, unlike the previous methods on single phase analysis, the inverter used in active filter is analyzed more precisely, i.e., the simultaneous three- phase analysis. The ohmic effect of phase-inductances is also taken into account. The inverter control system makes use of two internal and external loops. The external loop produces suitable signal for on/off switching through sliding mode control. The internal loop utilizes energy feedback to adjust the capacitor voltages. This new method effectively improves the speed of dynamic filter response in comparison with the previously reported methods and is able to quickly compensate harmonics and load unbalancing.
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