Abstract
The problem of voltage regulation in unknown constant resistive loads is addressed in this paper from the nonlinear control point of view for second-order DC-DC converters. The converters’ topologies analyzed are: (i) buck converter, (ii) boost converter, (iii) buck-boost converter, and (iv) non-inverting buck-boost converter. The averaging modeling method is used to model these converters, representing all these converter topologies with a generalized port-Controlled Hamiltonian (PCH) representation. The PCH representation shows that the second-order DC-DC converters exhibit a general bilinear structure which permits to design of a passivity-based controller with PI actions that ensures the asymptotic stability in the sense of Lyapunov. A linear estimator based on an integral estimator that allows reducing the number of current sensors required in the control implementation stage is used to determine the value of the unknown resistive load. The main advantage of this load estimator is that it ensures exponential convergence to the estimated variable. Numerical simulations and experimental validations show that the PI passivity-based control allows voltage regulation with first-order behavior, while the classical PI controller produces oscillations in the controlled variable, significantly when the load varies.
Highlights
Nowadays, the electrical distribution networks include direct current (DC) network operation with low- and high-voltage applications
The DC grids are more efficient and easier to operate than the alternating current networks since they should only be interested in controlling the active power and regulating the node DC voltages, while the concepts such as control of the reactive power or frequency disappear [3,4]
The converters can control the variables of these technologies; for this reason, the study of the control strategies of DC converters has become an essential focus. These strategies manage all the state variables of the DC grids, permitting the execution of the primary and secondary control stages [6]. This indicates that the power electronic converters and their controls are important to the operation of DC grids
Summary
The electrical distribution networks include direct current (DC) network operation with low- and high-voltage applications. DC-DC converters topologies lies in the fact that the modern electrical networks operated in with the DC technologies involves most of these converters in different isolated or connected grid applications [23] Some of these applications are battery chargers [24,25], photovoltaic generation [26,27], and voltage-controlled loads [28,29], among others, which implies that a generalized control strategy can be used indifferently of the application ensuring stability during closed-loop operation. To reduce the number of current sensors, we employ a linear integral load estimator that ensures exponential convergence to the unknown resistive load value, making our proposed PI-PBC design an adaptive controller with a reduced number of sensors This control approach shows excellent numerical performance compared with classical PI designs in both simulated and experimental cases.
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