F. Guinjoan

Sliding-mode control design of a boost-buck switching converter for AC signal generation

This paper presents a sliding-mode control design of a boost-buck switching converter for a voltage step-up dc-ac conversion without the use of any transformer. This approach combines the step-up/step-down conversion ratio capability of the converter with the robustness properties of sliding-mode control. The proposed control strategy is based on the design of two sliding-control laws, one ensuring the control of a full-bridge buck converter for proper dc-ac conversion, and the other one the control a boost converter for guaranteeing a global dc-to-ac voltage step-up ratio. A set of design criteria and a complete design procedure of the sliding-control laws are derived from small-signal analysis and large-signal considerations. The experimental results presented in the paper evidence both the achievement of step-up dc-ac conversion with good accuracy and robustness in front of input voltage and load perturbations, thus validating the proposed approach.

Application of sliding-mode control to the design of a buck-based sinusoidal generator

This paper is devoted to the design of a sliding-mode control scheme for a buck-based inverter, with programmable amplitude, frequency, and DC offset, with no external sinusoidal reference required. A general procedure for obtaining an autonomous (time independent) switching surface from a time-dependent one is presented. For this surface, the system exhibits a zeroth-order dynamics in sliding motion. On the other hand, from the sliding-domain analysis, a set of design restrictions is established in terms of the inverter output filter Bode diagram and the output signal parameters (amplitude, frequency and DC offset), facilitating the subsequent design procedure. The control scheme is robust with respect to both power-stage parameter variations and external disturbances and can be implemented by means of conventional electronic circuitry. Simulations and experimental results for both reactive and nonlinear loads are presented.

Energy-Balance Modeling and Discrete Control for Single-Phase Grid-Connected PV Central Inverters

This paper presents a two-control loop design considering the nonlinear time-varying characteristics of a single-phase grid-connected photovoltaic (PV) full-bridge central inverter. The control scheme design is based on the energy-balance modeling of the PV system and enables the design of a voltage loop linear discrete controller ensuring the stability of the system for the whole range of PV array operating conditions. A set of experimental results carried out on a laboratory prototype is provided to validate the proposed approach.

Analysis and design of H/sub /spl infin// control of nonminimum phase-switching converters

The application of the H/sub /spl infin// theory to control nonminimum phase dc-to-dc switching converters is investigated in this paper. Using an averaged linear model of the converter, a robust controller is developed, guaranteeing stability and the desired closed-loop dynamic response. Boost and buck-boost converters with H/sub /spl infin// control exhibit excellent performances with good tracking and high rejection capability of disturbances introduced by changes of load and input voltage by computer simulation. Experimental results are also obtained in a boost converter and compared with those obtained using current peak control and sliding-mode control.

Power Adaptor Device for Domestic DC Microgrids Based on Commercial MPPT Inverters

This paper presents a power adaptor device, referred to as smart panel device, allowing the connection of additional energy sources and storage elements to a domestic photovoltaic (PV) grid-connected system. The adaptor output port is designed to behave as a power source/sink, thus enabling its hot-swap parallel connection to renewable power sources without modifying their maximum power point (MPP). Moreover, the adaptor device features a power characteristic with a single controllable MPP and allows the control of the injected power within the operating range of the dc-ac grid-connected inverter. The work presents the design principles of such device by describing the operation of a sliding-mode controlled quadratic-boost converter. The proper operation of the device is experimentally verified for several scenarios in a small PV-based microgrid system including a fuel-cell stack, a 1-kW three-phase wind turbine, a battery charger-discharger, and commercial grid-connected PV inverters.

Large-signal modeling and simulation of switching DC-DC converters

A general nonlinear continuous formulation procedure for large-signal analysis of switching DC-DC converters is presented. The method can be applied in either of the two conduction modes, and it is easily programmed for computer-aided analysis with small simulation time. A boost regulator operating in constant-frequency current-programmed mode is used to illustrate the application of the method. A stability graph is subsequently developed to facilitate the design of DC-DC switching regulators for large-signal applications. The graph provides an estimation of the values of input voltage and load resistance leading to a stable regulator behavior.

Linear state-feedback control of a boost converter for large-signal stability

The problem of stabilizing a boost regulator in large-signal situations using linear control laws is derived by means of a circuit-oriented procedure. After establishing a large-signal circuit model for the boost regulator including state-feedback, conditions for passivity in the resulting two-port are studied. As a consequence, a linear control law is derived, thus ensuring regulator global stability even if the control saturation is taken into account. Subsequently, a linear analysis is performed, in order to design the desired dynamics and robust behavior of the switching regulator. The nonlinear analysis shows that only one feedback gain is necessary, provided that the coordinates of the equilibrium point are known. The use of regulator root locus allows one to choose the proper value of this gain. Simulations and experimental results verify the analytical predictions.

Interleaving Quasi-Sliding-Mode Control of Parallel-Connected Buck-Based Inverters

An interleaving fixed-switching-frequency quasi-sliding control algorithm based on the zero average dynamics approach is reported and applied to the design of a modular system of parallel-connected single-phase inverters. This approach is used in a laboratory prototype of three inverters with field-programmable gate array control-based implementation embedding this algorithm, as well as a power management strategy for handling the number of active inverters. Experimental results are provided to illustrate the design features in terms of AC output voltage regulation, balanced current sharing among mismatched modules, interleaved fixed-switching-frequency operation and robustness with respect to load variations, and inverter activation during system operation.

Identification and control of power converters by means of neural networks

This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications.

Discontinuous conduction mode in the SEPIC converter

The steady-state and dynamic analysis of the SEPIC converter in the discontinuous conduction mode by means of averaging techniques is considered. As a result, similar behavior to that of the Cuk converter was found. It is noted that the results obtained can be used for the optimum design of switching regulators using a SEPIC converter as a power stage.<<ETX>>