Problems in Switched-Mode DC and AC Power Conversion

Author: Barzegar, Farhad, Farhad

Year: 1983

Degree: Dissertation (Ph.D.)

Advisors: Cuk, Slobodan; Middlebrook, Robert David

Committee Members: Wilts, Charles Harold; Martel, Hardy Cross; Caughey, Thomas Kirk; Cuk, Slobodan; Middlebrook, Robert David; Nicolet, Marc-Aurele

Option: Electrical Engineering

DOI: 10.7907/qr7n-cj36

Abstract

Several issues in the field of Power Electronics are discussed in this thesis. Part I first reviews the method of state-space averaging to analyze steady state and small-signal behavior of switched-mode dc-to-dc converters. The approach is then generalized to encompass multiple inputs and a general form of feedback system. Since the method involves matrix manipulations it is well suited for computer computation. The Switching Converter Analysis Program is developed to implement the state-space averaging method, and requires computational power only of a small desktop computer. This, together with another program which performs frequency response measurement of the actual system, constitute a powerful design tool for power electronics engineers.

Part II extends the basic one-quadrant switching dc-to-dc converter to both current and voltage bidirectionality. The proposed "push-pull" power amplifier, being a four-quadrant converter, is capable of interfacing dc and ac ports. This special capability is then exploited to introduce a single-stage ac Uninterruptible Power Supply (UPS), which can process power from dc to ac or from ac to dc. Since with the form used only one of these accomplishments is required at a time, a single converter performs as a complete system. Hence, this UPS system is reliable and economical.

Finally, Part III further generalizes the switching power amplifier to polyphase operation in such a way that a minimal number of power converters is required. Then, through a set of steps a new polyphase power amplifier is introduced. The idea is experimentally verified by a 1 hp variable-speed motor drive with regulated output voltages. The technique has many other advantages such as ease of paralleling, dc isolation, and voltage boost, etc. The generality of the technique makes it suitable for many other line related applications such as uninterruptible power supplies, unity power factor battery chargers, and battery-to-three-phase line interfaces.

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