SIMULATION AND EXPERIMENTAL VALIDATION OF MULTI PULSE AC/DC CONVERTER FOR MEDIUM VOLTAGE ASDs

Abstract

In this dissertation work a 24-Pulse Buck-Boost AC/DC Converter is discussed. The objective of presented dissertation work is to simulate 24-pulse buck-boost AC/DC converter in MATLAB, and to validate experimentally the voltage regulation and power quality of the converter from utility side. In the proposed scheme, phase shifted transformer is used in which secondary (that supply the power cells i.e. cascade single phase VSI modules in each phase of the A.C. motor) are wound to obtain small phase angle between them. The phase angle differs by multiples of 200 for 2.4 KV drives; multiples of 150 for 3.3 KV drives & by multiples of 12° for 4.6 KV drive. They cancel most of the harmonic currents drawn by individual power cell so that primary current are nearly sinusoidal & confirm to or approaches to IEEE power quality standards 519 -1992. The proposed scheme also take care of unbalancing in secondaries winding voltage of phase shifted transformer or fluctuation in supply voltage. Developed converter maintains constant DC voltage of all the modules for entire range of supply voltage. Harmonic spectrum of input current, power factor of supply side also tested. A simulation model is developed in MATLAB for different topologies and also for proposed scheme to compare the results and to obtain the performance comparison. Simulation results are also verified with experimental results and these are found satisfactory.