The closed-loop control of a series dual bridge GTO voltage source converter

A need for stable controllable converters operating at increasing voltage levels, and working at unity power factor with decreased harmonic current content, exists in the industry at the present time. Multilevel topologies which have been considered in the past are able to address the needs stated above, but they become increasingly more complex to construct and to control as the number of stages is increased. On the other hand, modular structures consisting of series dual bridge voltage source converters are far less complex in construction when contrasted to that of a multilevel topology. The challenge is to design a control loop structure which has sufficient relative stability.;In a control context, a series dual bridge GTO voltage source converter system appears as a multi-input-multi-output sixth-order plant model. The control approach taken in this thesis is to use state feedback to improve the relative stability. This is achieved by developing a generalized procedure for obtaining the desired pole locations using the asymptotic pole assignment method. Asymptotic pole assignment is able to accomplish exact or quasi-exact zero-pole cancellations.;The MATLAB software package is used for the small signal design. The experimental test plan for large signal closed-loop performance of a series dual bridge GTO voltage source converter using PECAN (Power Electronic Circuit Analysis package) is described in some detail.;The analysis shows that state feedback will significantly improve the overall stability, relative and dynamic performance of a series dual bridge GTO voltage source converter.