Non-linear predictive control of a DC-to-DC converter

In this paper we develop a non-linear predictive controller for regulating DC-DC power converters. The proposed control strategy is implemented and tested using two models: an averaged non-linear model for control purposes and a switched Buck-Boost circuit model as the controlled plant. A comparison with classical PID control in terms of start-up behavior and robustness to disturbances is given in order to outline the performance of the predictive controller. This work has been partially financially sponsored by the Dutch Science Foundation (STW), Grant “Model Predictive Control for Hybrid Systems” (DMR.5675). 1. INTRODUCTION Some of the most important circuits within the family of power circuits are the DC-DC converters. They are extensively used in power supplies for electronic equipment to control the energy flow between two DC systems (e.g. well-regulated DC-to-DC power converters are critical for mission success on space platforms). Control of a DC-DC converter power circuit is based, explicitly or implicitly, on a model that describes how control actions and disturbances are expected to affect the future behavior of the plant. Usually, the control problem consists in defining the desired nominal operating condition, and then regulating the circuit so that it stays close to the nominal, when the plant is subject to disturbances and modelling errors that cause its operation to deviate from the nominal. Typical control system configurations for power circuits include open-loop as well as closed-loop control strategies. In both cases, PID controllers are utilized, which can be designed using classical methodologies based on the Nyquist stability criterion and Bode plots or tuned with Ziegler-Nichols techniques. The controller must keep the DC-DC converter within a certain percentage of the specified nominal operating point in the presence of disturbances and modelling errors. Unfortunately, PID control does not always fulfil the above mentioned control specifications, especially when disturbance rejection and transient response time requirements are concerned, due to the highly non-linear characteristics of the DC-DC converters. As a result of this fact, there is much interest in developing more intelligent and robust