2.  Introduction  Problem Definition & Literature Review  Main circuit  References

3. The increasing use of power electronic equipments in a distribution network which represent nonlinear loads have caused many power quality disturbances such as harmonics pollution, unbalanced load currents, and reactive power problems. As a result poor power factor, weakening efficiency, over heating of motors and transformers, malfunction of sensitive devices etc. [1]-[4] are encountered.

4.  Conventionally, a passive power filter which consists of passive elements is used to provide harmonic filtering as an economical and effective filtering device.  However it has shortcomings such as fixed compensation performance, bulk in size and resonance troubles [5]-[9].

5.  Important types of passive power filters and their configurations are discussed in [5].  To overcome the shortcomings of passive power filters and to mitigate the power pollution in networks caused by the nonlinear loads, an active power filter (APF) was established in around 1970s [10]-[13].

6.  APFs are previously not implemented in power net works, because of unavailability of high speed power switching devices.  Recently the power electronic development spurred the interest in IGBTs, MOS-FETs etc [11] and then APFs are developed incorporating power electronics technology to support the needs of industry.

7.  With the development of power electronic technology, low voltage and high current switching power supply has been applied widely in production and life.  Generally, there are two methods to eliminate harmonics, which are mainly passive power filter and active power filter. The former is relatively low cost, but filtering effect is far from desirability.  This paper employs active power filter to suppress harmonic current of low voltage and high current(60V/500A) switching power supply.

10.  [1] Dayi Li, Jun Tian, “A novel active power filter for the voltage-source type harmonic source”, Electrical Machines and Systems, pp.2077-2080, 2008.  [2] Dawei Gao, Qingchun Lu, “Design and performance of an activepower filter for unbalanced loads”, Power System Technology, vol4,pp.2496-2500, 2002.  [3] Hurng-Liahng Jou, Jinn-Chang Wu, “A novel active power filter for harmonic suppression”, Power Delivery, vol20, pp.1507-1513, 2005.  [4] Izhar, M, Hadzer, “Performance for passive and active power filter in reducing harmonics in the distribution system”, Power and Energy Conference, pp.104-108, 2004.

11. Thank You