Three phase AC to AC Z-source converter

Abstract

With the increasing research in power converters, there is a thrust on finding the solution to obtain a more efficient buck-boost converter which can transfer AC to AC directly with the minimal component requirement. For this the concept of impedance source converter is used. A Z-source network has an advantage over traditional converters like voltage source (V-source), current source (I-source) and push-pull converters that it can operate in shoot-through state which helps to boost the output voltage. The simulation work for three phase AC to AC Z-source converter has been carried out and the results are verified mathematically. The converter has some limitations like maximum obtainable boost factor is 1.15. This limitation is eliminated in improved topology having twelve bidirectional switches. Though the number of switches required in improved topology is doubled, the maximum obtainable boost factor is very high (in our case boost factor obtained is 1.8). In the thesis work a thorough analysis and comparison of the two converters are presented. Both converters voltage sag and swell capabilities are verified by simulation and mathematical results. State space averaging technique for mathematical modelling of both the converters. The closed loop analysis of the two converters is tried and simulation results are presented in support of that. Further, frequency control is also possible in both the converters which is not presented in this thesis.