TABLE OF CONTENTS Domingo Biel Sol and Enric Fossas Colet
Power converters are widely used in applications where it is desired to obtain a totally regulated electric signal from a non-regulated one, keeping optimum energy efficiency in the conversion. These converters can be linear or switched, the latter being the most common due to their better energy efficiency. As will be seen in this chapter, switching converters can be modelled as variable structure systems. They therefore constitute a natural field of application of Sliding Mode Control techniques. The most usual conversion types, namely DC-DC, DC-AC and AC-DC, will be considered here. SMC controllers will be designed and several aspects involving the electronic implementation of the controllers will be discussed.
The aim of DC-DC power conversion is to obtain a regulated, continuous voltage (or current) at the load terminals. The power regulator consists of a power stage composed of semiconductors, inductors and capacitors, and a control stage commonly based on the processing of an error signal (the difference between a reference and an output voltage) and a voltage-time conversion through a Pulse-Width-Modulator (PWM). The control objective is to achieve a regulated robust output voltage with good dynamic performance from the switching converter.
The ideal [1] buck, boost and buck-boost topologies feeding a resistive load are depicted in Figs 12.1 and 12.2. The converter dynamics is modelled by two state-variables, i, the inductor current and v, the capacitor voltage [2], and...
