INTERNATIONAL JOURNAL OF RESEARCH IN COMPUTER APPLICATIONS AND ROBOTICS www.ijrcar.com Vol.2 Issue.11, Pg.: 1-12 November 2014 K.Varalakshmi et al Page 1 INTERNATIONAL JOURNAL OF RESEARCH IN COMPUTER APPLICATIONS AND ROBOTICS ISSN 2320-7345 Multilevel Converter STATCOM Fault Tolerance Capability K.Varalakshmi 1 , Dr.R.L.Narasimham 2 Dr.G.Tulasiramdas 3 1 Associate proffersor, EEE department, TKR Engg. College, HYD, vara1981@gmail.com 2 Professor, EEE department, Andhra University, rl_narasimham@yahoo.com 3 Vice chancellor, JNTU-Kakinada, vc_das@yahoo.co.in Abstract Fault tolerant capability of multilevel converters in STATCOM (static synchronous compensator) has been utilized as power system controller for reactive power compensation and voltage regulation improvement. The advantages of the multilevel structure for The STATCOM are 1) Elimination of bulky transformers.2) Reduction of the output harmonic levels by Synthesizing Sinusoidal voltage 3) lower switching losses. The structure has only one disadvantage that is increased switch failure, due to the increased number of switches. A single switch failure, however, does not necessarily force an (2n + 1)- level STATCOM offline. Even with a reduced number of switches, a STATCOM can still provide a significant range of control by removing the module of the faulted switch and continuing with (2n − 1) levels. This paper introduces an approach to identify the existence of the faulted switch, and reconfigure the STATCOM. This approach is illustrated on 13 level converters STATCOM and total harmonic distortion is analyzed by using MATLAB. Keywords- Statics synchronous compensator (STATCOM), Cascaded H-Bridge, fault detection, phase shift pulse width modulation (PSPWM). I. INTRODUCTION The static synchronous compensator (STATCOM) a FACTS device, using voltage source converters has been widely accepted to improve power system operation. In bulk power systems, they are indispensable to stabilize the power system and maintain the bus voltage. Several STATCOM’s based On GTOs and zigzag transformers have been developed and put into operation within the last 10years.Typically 48 pulse consists of eight voltage source converters connected through 8zig-zag transformers are most expensive components in the system .one popular method to eliminate the bulky transformers is to use multilevel converters .The General structure of multilevel converters is to synthesize a staircase waveform, typically obtained from capacitor voltage sources [1].The advantages of cascaded H-bridge multilevel topology for The STATCOM are 1) reactive-power compensation 2) lower harmonic injection into the power system. 3) Decreased stress on the electronic components due to decreased voltages. 4) Increase of switching frequencies and the use of PWM techniques.