Hugo Valderrama-Blavi

Robust Sliding-Mode Control Design for a Voltage Regulated Quadratic Boost Converter

A robust controller design to obtain output voltage regulation in a quadratic boost converter with high dc gain is discussed in this paper. The proposed controller has an inner loop based on sliding-mode control whose sliding surface is defined for the input inductor current. The current reference value of the sliding surface is modified by a proportional-integral compensator in an outer loop that operates over the output voltage error. The stability of the two-loop controller is proved by using the Routh-Hurwitz criterion, which determines a region in the Kp-Ki plane, where the closed-loop system is always stable. The analysis of the sliding-mode-based control loop is performed by means of the equivalent control method, while the outer loop compensator is derived by means of the Nyquist-based Robust Loop Shaping approach with the M-constrained Integral Gain Maximization technique. Robustness is analyzed in depth taking into account the parameter variation related with the operation of the converter in different equilibrium points. Simulations and experimental results are presented to validate the approach for a 20-100-W quadratic boost converter stepping-up a low dc voltage (15-25-V dc) to a 400-V dc level.

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.

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.

Self-oscillating DC-to-DC switching converters with transformer characteristics

Fourth-order converters with both input and output filters are analyzed in self-oscillating sliding mode. The boost converter with output filter and the Cuk converter are shown to have stable dynamics and an equilibrium point with transformer characteristics. The analytical predictions are verified by experimental results.

Sliding-Mode-Control-Based Boost Converter for High-Voltage–Low-Power Applications

This paper presents the analysis and design of a very high-voltage-gain single-stage boost converter operating at the boundary between continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The converter is supplied by a 12-V car battery and attains 1200 V with a voltage gain of 100. The use of a hysteretic comparator in the control loop precludes the risk of modulator saturation and facilitates the operation at the mentioned boundary. Sliding-mode control theory is applied to analyze the dynamic behavior of the switching regulator and to establish the system stability conditions. The performance of the converter is investigated using silicon carbide (SiC) devices for the power switch realization. LED-based efficient lighting systems can be a promising application of the proposed system.

A High-Voltage SiC-Based Boost PFC for LED Applications

This paper reports a single-stage grid-supplied boost converter with power factor correction (PFC) for LED-applications using Silicon-Carbide (SiC) and operating at the boundary between continuous and discontinuous conduction modes (CCM-DCM) to reduce switching losses. The converter is supplied by a 230 Vrms grid voltage, and attains 1200 V DC at the output port, where a-spot of 320 LEDs connected in series is supplied at constant current. Sliding-mode control theory is employed to analyze the switching regulator dynamics, assuring the system stability. The controller is easily implemented by means of a hysteretic comparator avoiding the risk of modulator saturation. The power switch is realized with silicon carbide (SiC) devices to improve the performance of low-power -grid -supplied LED-based lighting systems. The experimental results are in perfect agreement with the theoretical predictions and demonstrate the feasibility of the proposed approach.

Adapting a low voltage PEM fuel-cell to domestic grid-connected PV system

In this work, we present an electronic system that simplify the incorporation of additional sources to a previously existent small PV system. Particularly, we investigate how to proceed with a low voltage, high-current PEM fuel-cell. The proposed system is developed from the concept of loss-free resistor, and can be easily adapted to any type of energy source and storage elements. Among the advantages of the proposed system, the PV array keeps its maximum power point (MPP), with independence of the power delivered by the new source. In addition, the proposed system allows also a particular MPPT for the new source if required. Finally, as additional benefits, sources can the incorporated or extracted with hot-swapping, and the energy production profile can be smoothed, predictable, and even constant, as wanted by the utility grid regulators.

Sliding-mode control of a transformer-less dual-stage grid-connected photovoltaic micro-inverter

A transformer-less topology of a grid-connected photovoltaic micro-inverter applying sliding-mode control is discussed in this paper. The proposed structure is a dual-stage topology with a quadratic boost converter in the DC-DC stage and a full-bridge inverter in the DC-AC stage. The quadratic boost uses a multi-loop scheme with a sliding-mode current controller and a proportional-integral (PI) compensator regulating the output voltage. The full-bridge inverter injects real power to the grid by means of a sinusoidal reference sliding-mode tracking-loop whose amplitude is defined by a maximum power point tracker (MPPT). This preliminary work involves an analytical discussion and several simulation results of each converter and of the overall system.

Modular-based PFC for low power three-phase wind generator

Hybrid Distributed systems include many sources, storage elements, and various local loads, connected to a common distribution bus. In this work, different matching methods to adapt a 3-phase wind alternator to a variable DC-bus are reviewed, and finally a modular solution based on single-phase Boost-based PFCs is proposed. Nevertheless, Boost modules must be adapted to operate with non-isolated sources, like 3–4 wire, 3-phase generators. Magnetic coupling is introduced here to enhance the isolation among phases, reducing also converter losses and size. Sliding mode approach has been applied to the whole converter as a single unit, to verify that independent regulation of all phase modules was possible, even sharing a common output capacitor. To verify the theoretical analysis, a 1.5 kW prototype has been built confirming independent phase control and good sinusoidal input waveforms.