Problems in Analysis, Control, and Design of Switching Inverters and Rectifiers

Citation

Mahadevan, Ramaswamy (1987) Problems in Analysis, Control, and Design of Switching Inverters and Rectifiers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2R9K-A588. https://resolver.caltech.edu/CaltechETD:etd-03052008-091727

Abstract

Control and analysis techniques in switched-mode inversion (dc-ac) and rectification (ac-dc) are examined in this thesis. Current programming and sliding mode control are used to provide regulation and obtain desired dynamic responses. The basic buck, boost, flyback, and buck-boost topologies are used to illustrate the different methods of control and analysis. For illustration, embodiments employ fast switching converters, but the techniques described can be applied to any general converter.

Different possibilities for the current programming of dc-ac inverters and ac-dc rectifiers are explored and the more practical and advantageous methods noted. Current reference programming improves the dynamic response of the converter and simplifies the design of the main regulatory loop. It also protects the switches from excessive current stresses and enables the parallel operation of many converters to support a common load. Constant frequency current reference programmed converters are, however, subject to oscillations under certain operating conditions.

Describing equations are used to obtain the low frequency characterization of current programmed converters. The system representation is first obtained in the stationary abc reference frame and then transformed to the rotating dq coordinate frame. In the dq coordinate system, the low frequency characterizations of all balanced, polyphase ac converter systems are represented by a set of continuous, time-invariant differential equations. The steady-state and linearized, small signal dynamic responses are then obtained in this rotating reference frame.

Sliding mode control is applied to inverters and rectifiers to provide regulation and ensure the stability of the system in the presence of small and large signal disturbances. This is a natural method of control for variable structure systems and enables the design of a robust controller that can provide stability and performance in the face of plant uncertainities. However, it requires that all or many of the states of the system be accessible and results in a variable switching frequency in the converter.

The equivalent control method is used to obtain the low frequency properties of the sliding mode system, and can also be used to obtain the low frequency models of duty ratio programmed converters. Different switching strategies can be used to provide sliding mode control, as well as to optimize responses, maximize efficiency, or minimize switching losses. Practical aspects such as hardware implementation, switch realization, and measurement techniques are also discussed.

Thesis Files