In this paper a 48-pulse uncontrolled AC-DC converter is proposed to mitigate AC line current harmonics of the input side. The proposed rectifier uses conventional 24-pulse parallelly connected rectifier with addition of a passive current injection circuit named as special interphase reactor. The interphase reactor consists of two additional lower rated power diodes. The value of the found THD is 3.55% which satisfies the IEEE 519-1992 standard. Proposed converter also shows lower fluctuation of harmonics valued 1.40% with respect to full load ensuring stable operation at light load. Designed multipulse converter scheme is also simple in construction and requires less number of electronic devices compared to conventional 48-pulse AC-DC converter. This article also explains the simulation and THD performance of the proposed AC-DC converter with proper figures.
Słowa kluczowe: Total harmonic distortion (THD), Zigzag transformer, MATLAB simulink, Special interphase reactor (SIPR).
W artykule przedstawiono 48-pulsowy przekształtnik AC-DC ze zmniejszoną wartością harmonicznych prądu na wejściu. Proponowany prostownik wykorzystuje 24-pulsowe konwencjonalne prostowniki połączone równolegle z dodatkiem obwodu prądowego nazwanego międzyfazowym reaktorem. Składa się on dwóch dodatkowych diod. Osiągnięto współczynnik THD mniejszy niż 3.55%. Proponowany układ charakteryzuje sie też mniejszą fluktuacja harmonicznych.
Keywords: przekształtnik AC-DC, wspołczynnik THD
AC-DC converters are basically known as rectifiers. With the increasing electricity demand of the present world harmonics is caused mainly due to the inclusion of nonlinear loads in modern power systems. So, harmonics are generated by almost all types of converters resulting remarkable problems on AC mains, loads and distribution systems -. This harmonics problem becomes more severe at light load i.e. 20% of the full load . Therefore the suppression of the harmonics to control the total harmonic distortion (THD) in allowable ranges referred to known standards is designated as a very important matter in modern power system . For reducing the harmonics of the input AC line current, different types of filters such as active filters and passive filters have been proposed in different rectifier schemes - . But there are some problems occured while working with passive filter such as introduction of series or parallel resonance, unpredictable filter current, reactive power generation and bulkiness of the device alongside active filters have strict limitation on switching frequency of the electronic devices [8-9]. Voltage source converter (VSC) based multipulse rectifiers are also being used for harmonics mitigation and applicable to HVDC systems but these types of schemes also suffer with very high switching frequency of the electronic devices . Increasing the pulse number of a rectifier by pulse doubling or pulse tripling techniques are also popular choices for mitigating harmonics [11-12]. Controlled as well as uncontrolled multipulse rectifier (MPR) schemes can also be used for reducing harmonics but controlled rectifier schemes come with many undesirable facts like reactive power generation, current ripple, need of power filters, extra circuitry requirement for generating gate pulse etc. [13-14]. So, it is flexible as well as a cost effective approach to use passive or uncontrolled rectifiers for harmon [...]
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