In this paper we present, an experimental comparative study of five controllers for boost dc-to-dc convert.ers recently reported in the control literature. For all these algorithms local asymptotic stability of the desired equilibrium is insured. To carry out the experiments we coinstructed a low cost electronic card, which captures the essential features of a commercial product. The algorithm:; are compared with respect to ease of implementation, in particular their sensitivity to the tuning parameters, and closed-loop performance. The latter is evaluated with the standard criteria of steady-state and transient behaviour to steps and sinusoidal references, and attenuation of disturbances in the power supply and sens,itivity to unknown loads. Motivated by the experimental evidence we propose several modifications to the basic schemes, for some of them we establish some new theoretical results.

Passivity-based control (PBC) has shown to be very powerful to design robust controllers for physical systems described by Euler-Lagrange (EL) equations of motion. The application of PBC in regulation problems of mechanical systems yields controllers that have a clear physical interpretation in terms of interconnection of the system with its environment. In particular, the total energy of the closed-loop is the difference between the energy of the system and the energy supplied by the controller. Furthermore, since the EL structure is preserved in closed-loop, PBC is robust vis ci vis unmodeled dissipative effects. Unfortunately, these nice properties are sometimes lost when PBC is used in other applications, for instance, in electrical and electromechanical systems. In this paper we further contribute to develop a new PBC theory encompassing a broader class of systems, and preserving the aforementioned energy-balancing stabilization mechanism and the structure invariance, continuing upon our work in [14], [9] and [17]. Towards this end we consider port-controlled Hamiltonian systems with dissipation (PCHD), which result from the network modeling of energy-conserving lumped-parameter physical systems with independent storage elements, and strictly contain the class of EL models.

This paper presents a passivity-based controller for a Distribution Static synchronous Compensator (D-Statcom) aimed at compensating reactive power and unbalanced harmonics in the general case of distorted and unbalanced source voltages and load currents. The proposed approach is based on the measurements of line currents, and ensures precise compensation for selected harmonics. Moreover, in order to compensate for the unavoidable uncertainty in certain system parameters, adaptation is added to the passivity-based controller. One of the major advantages of the proposed solution compared to conventional alternatives is that we are able to perform precise tracking (including higher order harmonics) even in the presence of a relatively low switching frequency, i.e., in the presence of an inverter with limited bandwidth. Simulation and experimental results are provided to illustrate the merits of our solution.

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The problem of regulating the output voltage of the Boost DC-to-DC power converter has attracted the attention of many control researchers for several years now. Besides its practical relevance, the system is an interesting theoretical case study because it is a switched device whose averaged dynamics are described by a bilinear second order non-minimum phase system with saturated input, partial state measurement and a highly uncertain parameter -the load resistance-. In this paper we provide a solution to the problem of designing an output-feedback saturated controller which ensures regulation of the desired output voltage and is, at the same time, insensitive to uncertainty in the load resistance. Furthermore, bounds on this parameter can be used to tune the controller so as to (10-cally) ensure robust performance, e.g., that the transient has no (under)over-shoot. The controller, which is designed following the energy-balancing methodology recently proposed by Ortega, van der Schaft and Maschke, is a simple static nonlinear output feedback, hence it is computationally less demanding than the industry standard lead-lag filters. Problem formulationThe averaged model of the DC-to-DC Boost converter depicted in Fig. 1 is given by [3 ], [4](1.1)c 1 1 x 2 = --x 2 + -u x 1 rC L 4 0 ) = (21(0), 2 2 ( 0 ) ) E R ? o where x 1 is the inductance flux, 2 2 is the charge in the capacitor voltage, and U is the continuous control signal, which represents the slew rate of a PWM circuit controlling the switch position in the converter. The positive constants C, L , r, E are the capacitance, 'This work has been partially supported by CONACyT of 2Author to whom all correspondence should be addressed. Mexico inductance, load resistance, and voltage source, respectively, and 7Z:o denotes the open first quadrant. The u = o Figure 1: Boost converter circuit. following conditions of operation of the device are imposed by technological considerations: C . l The only signal available for measurement is 2 2 . C.2 The control signal U ranges in the set (0,l). C.3 The state vector 2 lives in R;,. C.4 All parameters, except the load resistance r , are known. The control objective is to regulate the output capacitor voltage & 2 2 to a desired constant value V, > E , verifying the conditions C.l-C.4.The main contribution of this paper is to show that the energy-balancing methodology recently proposed in [5] yields a solution to this problem. Furthermore, the resulting controller is a simple static nonlinear output feedback, hence it is computationally less demanding than (even) the industry standard lead-lag filters. Remarks1. If we fix U to a constant value, the equilibria of (l.l), (1.2) (denoted Z), verify the algebraic relation (1.3) L Z1= -T E C 2 2 2 2 Hence, if we fix 6 5 2 at the desired output voltage V,, we get the equilibrium point we want to stabilize x+ and the corresponding constant control U* as L E rE V* (1.4) 2* = ( 2 1 * , 2 2 * ) = (-V,", CV*), U* = -0-7803-5250-5/99/$10.00 0 1999 IEEE 2100