Romeo Ortega

A saturated output feedback controller for the three phase voltage sourced reversible boost type rectifier

In this article, the authors present a saturating controller to regulate the output voltage load in a three-phase boost type rectifier. The controller only needs the output voltage signal to be implemented. Moreover, by forcing the inductance currents to track desired suitable sinusoidal signals in phase with the input source voltages, the controller can ensure near unity power factor functioning of the system. The saturation feature in this controller is motivated by the fact that the allowed combinations of switches in the rectifier circuit define a finite set of allowed control vectors, moreover, the convex combinations of these vectors raise up a convex hull in the space of control inputs, a hexagon in this example. Thus, based upon the assumption of fast switching, one can ensure that any control vector lying inside this hexagon, and much more, inside its inscrit circle, can be physically implementable by means of a PWM strategy or a convex combination of the allowed control vectors.

Control of Finite-Dimensional Port-Hamiltonian Systems

We discuss in this chapter a number of approaches to exploit the model structure of port-Hamiltonian systems for control purposes. Actually, the formulation of physical control systems as port-Hamiltonian systems may lead in some cases to a re-thinking of standard control paradigms. Indeed, it opens up the way to formulate control problems in a way that is different and perhaps broader than usual. For example, formulating physical systems as port-Hamiltonian systems naturally leads to the consideration of ‘impedance’ control problems, where the behavior of the system at the interaction port is sought to be shaped by the addition of a controller system, and it suggests energy-transfer strategies, where the energy is sought to be transferred from one part the system to another. Furthermore, it naturally leads to the investigation of a particular type of dynamic controllers, namely those that can be also represented as port-Hamiltonian systems and that are attached to the given plant system in the same way as a physical system is interconnected to another physical system. As an application of this strategy of ‘control by interconnection’ within the port-Hamiltonian setting we consider the problem of (asymptotic) stabilization of a desired equilibrium by shaping the Hamiltonian into a Lyapunov function for this equilibrium. From a mathematical point of view we will show that the mathematical formalism of port-Hamiltonian systems provides various useful techniques, ranging from Casimir functions, Lyapunov function generation, shaping of the Dirac structure by composition, and the possibility to combine finitedimensional and infinite-dimensional systems.