Development of a hybrid active/passive filter for dispersed installation on distribution power systems

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With significant development of power electronics technology, the proliferation of non-linear loads such as static power converters in a range of 50 W to 300 MW has deteriorated power quality in transmission/distribution systems. Notably, voltage distortion or voltage harmonics may approach or exceed its allowable level in power distribution systems. Individual electric power consumers and end-users are responsible for reducing current harmonics, while electric power companies or utilities are responsible for reducinging voltage harmonics at the point of common coupling in distribution systems.In this research, a hybrid active/passive filter of 0.32 kVA,based on three single-phase voltagefed PWM inverters of 0.13 kVA,was constructed to verify the effectiveness in damping of harmonic propagation. It was installed on a specially designed distribution system rated at 3phi, 200 V and 20 kVA.The following conclusions obtained are as follows :1. The 5th harmonic voltage at the receiving terminals is amplified by three times as large as that at the sending terminals on the distribution system. Such a harmonic propagation occurs as a result of harmonic resonance between the supply inductor and shunt capacitors for power factor correction.2. The hybrid active/passive filter has the capability of perfectly damping of the harmonic propagation.3. The required rating of the active filter is only 0.6%, compared to the distribution system rating of 20 kVA.