Constrained Optimal Control of the Step-Down DC-DC Converter

• Published in: IEEE transactions on power electronics Vol. 23; no. 5; pp. 2454 - 2464
• Main Authors: Geyer, T., Papafotiou, G., Frasca, R., Morari, M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-09-2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Automatic control; Circuit properties; Circuits; Convertors; DC-DC converter; DC-DC power converters; Electric currents; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrical machines; Electronic circuits; Electronics; Exact sciences and technology; Experiments; hybrid system; Inductors; Kalman filters; Load management; model predictive control (MPC); Optimal control; piecewise-affine (PWA) system; Power electronics; Power electronics, power supplies; Proportional control; Pulse width modulation converters; Regulation and control; Signal convertors; Switching converters; Voltage control; State feedback; Kalman filter; Control synthesis; Inductor; Modeling; Implementation; hybrid system; power electronics; Control constraint; Regulation(control); Output voltage; Frequency converter; Hybrid model; Mathematical model; Feedback system; Direct current convertor; piecewise- affine (PWA) system; DC-DC power convertors; Constrained optimization; Look up table; model predictive control (MPC); Step down convertor; DC-DC converter; Voltage standard; Photonic crystal; Optimal control; Reference voltage
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2008.2002057

In this paper, we propose a novel approach to the modeling and controller design of the synchronous step-down dc-dc converter. We introduce a hybrid converter model that is valid for the whole operating regime and captures the different modes of operation. Based on this model, we formulate and solve a constrained optimal control problem. This allows a systematic controller design that achieves the regulation of the output voltage to its reference despite input voltage and output load variations while satisfying the constraints on the duty cycle and the inductor current. The resulting state-feedback control law is of piecewise affine form, which can be easily stored and implemented in a lookup table. A Kalman filter is added to account for unmeasured load variations and to achieve zero steady-state output voltage error. Experimental results demonstrate the potential advantages of the proposed control methodology.