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A set of new nonlinear current control methods are presented for single-phase power factor corrected ac-dc converters. These control methods combine input current feedforward with partial feedback based on the switch current to achieve sinusoidal input current and unity input power factor. They overcome the limitations of conventional linear (average) current control in terms of control bandwidth and sensitivity to noise, resulting in high-performance input current control which can meet the most stringent harmonic current limits required by variable-frequency airborne power systems. The control methods are also ideally suited for integrated mixed-signal implementation, requiring an analog current controller which is very simple, much less sensitive to noise than conventional linear feedback control, and independent of converter and control design parameters; and a digital controller which operates with a sampling frequency much lower than the switching frequency. Detailed development of the control methods is presented along with their stability analysis and circuit implementation. A prototype converter and its operation are also presented to validate the analysis and to demonstrate the performance of the control methods.
Date of Publication: Nov. 2007