Harmonic neutralization in Unified Power Flow Controller (UPFC) installed power system using multi pulse structures

The continuous growth in the demand for electric power necessitates the flexibility of operation in power system. Of different power electronics-based Flexible AC Transmission System (FACTS) devices, which enhance the power transmission capabilities, Unified Power Flow Controller (UPFC) provides an emerging and promising solution for the power flow problems in the system, as it simultaneously and/or selectively controls the transmission parameters. The UPFC, in this paper, consists of two solid-state voltage source inverters which are connected through a common DC link capacitor. The basic problem of using static converters is the generation of harmonics. The simplest way of canceling harmonics in a system of converters and regulating the voltage is by means of coupling transformers or multilevel-multi pulse converters. This paper proposes the harmonic neutralization techniques, using multi-pulse converter structures for UPFC due to which the output voltage waveform approximates an ideal sine-wave as closely as desired, without any increase in the switching frequency. MATLAB SIMULINK is used to implement this idea. A comparison is made for the output wave forms obtained in 12, 24 and 48 pulse converter based UPFCs.