Fabrício Hoff Dupont

Reduced-Order Model and Control Approach for the Boost Converter With a Voltage Multiplier Cell

The boost converter with a voltage multiplier cell allows the static gain extension by means of the switching capacitor technique, reducing the duty cycle needed to achieve the same voltage gain when compared to the conventional boost converter. However, the modeling of this converter is complex and requires the use of advanced techniques due to the resonant inductor. Thus, this paper aims to present a reduced-order model of this converter without the resonant energy exchange between the capacitors, so that the state-space averaging technique can be applied assuming small ripple in the state variables. In addition, this paper presents the design of a control system for the boost converter with a voltage multiplier cell. The adopted strategy employs an inner loop to control the input current and an outer loop for the output voltage regulation. Extensive analysis based on simulations and an experimental prototype demonstrate that the proposed modeling, although simplified, is sufficient for an adequate control system design, ensuring good voltage regulation, and fast transient responses.

A methodology to obtain the equations for the calculation of the weighted average efficiency applied to photovoltaic systems

This paper analyzes the solar radiation profile of some Brazilian cities and shows a methodology to obtain the equations for the calculation of the weighted average efficiency, aiming to allow efficiency maximization designs for the electrical energy processing in photovoltaic systems. By means of data obtained in climatic stations that are members of the National Organization of Environmental Data System (SONDA) network, of the National Institute of Spatial Research (INPE), the electrical generation capacity of these stations is shown, and is verified that 70% of the processed energy lies in the range of 25% to 50 % of the nominal power of converter modules. The analysis presented in this paper has a major importance for the optimized design of power converters, and shows a strong dependence of the site location for the energy generation system.

Comparison of digital LQR techniques for DC-DC boost converters with large load range

This work presents a comparison of three state feedback controllers suitable for application to DC-DC boost converters with large load range. These converters are an important stage in several renewable source systems. The first controller is a conventional LQR designed for a single operating point. The second controller uses the switching between LQR controllers designed for a set of load conditions (local controllers). The third controller is a fuzzy logic based controller which is based on the convex combination of the local controllers. The second and the third controllers use the load current as a decision variable. The implementation of all controllers is carried out in a TMS320F2812 fixed-point DSP, considering the transport delay and the limitation of data format from this digital control platform. Simulation and experimental results obtained for the three control strategies submitted to load disturbances allow to observe the quality of the transient and steady state responses, leading to the conclusion of the superiority of the fuzzy logic based controller in terms of a better tradeoff between performance and spent of control energy.

Design and comparative analysis of multiple controllers applied to DC-DC converters with large load range

This paper presents a new controller design methodology for DC-DC converters operating with load varying in a large range. The proposed methodology employs a genetic algorithm to find LQR controllers with optimum performance by means of ITSE criterium and control action. A fuzzy logic based strategy is then employed to combine these local controllers, resulting in a strategy which guarantees good performance for a large range of load values. From Tellegen theorem, a load resistance estimator is obtained. The estimated resistance is used as the decision variable for the fuzzy supervisor controller. The proposed methodology is compared with the conventional LQR technique, based in a single controller, and with a controller switching strategy. Simulation results illustrate the superior performance of the converter with the application of the proposed methodology.

Multiple controllers for boost converters under large load range: A GA and fuzzy logic based approach

This paper presents a new methodology to design controllers for boost converters operating in a wide range of load variation. The proposed technique uses genetic algorithm to find local LQR controllers providing optimal performance in terms of overshoot and ITSE criteria. Fuzzy logic strategy is then used to combine these local controllers, yielding a strategy that guarantees good performance for a large set of load conditions. The proposed approach is compared with a conventional technique based on a single controller and with a strategy of switching controllers. Simulation results illustrate the superior performance of the converter with the proposed controller.

A DLQR designed by means of a genetic algorithm for DC-DC boost converters

In this work, a genetic algorithm is employed to design a discrete linear quadratic regulator (DLQR) for a boost converter subject to switched loads. The model of the converter takes into account a parasitic resistance, a delay from digital control signal implementation and an integral action over the error. A genetic algorithm is used to search and provide an optimal choice for the weighting matrices of the DLQR. The objective function of the algorithm is evaluated using data from a standard circuit simulator, allowing to easily include nonlinearities as quantization and saturation. The control law is implemented using a digital signal processor leading to goods experimental results, which are also superior to those from a conventionally designed DLQR.

A DLQR applied to boost converters with switched loads: Design and analysis

In this paper, the design and the experimental validation of a discrete linear quadratic regulator applied to boost converters with switched loads are investigated. The closed-loop system stability under arbitrary switching is ensured by means of the existence of a switched Lyapunov function, obtained by means of linear matrix inequalities, which is the main contribution of this work. The control law is implemented using a digital signal processor. Experimental results reveal the good transient and steady state performances as well as demonstrate a strong correspondence with the simulation, proving the practical viability of the proposed procedure.

Fuzzy control of a three-phase step-up DC-DC converter with a three-phase high frequency transformer

This paper presents a closed loop fuzzy logic control technique applied to three-phase step-up DC-DC converter with a three-phase high frequency isolation transformer. This converter was developed for industrial applications where the dc input voltage is lower than the output voltage, for instance, in installations fed by battery units, photovoltaic arrays or fuel cell systems. The converters main characteristics are: reduced input ripple current, step-up voltage, high frequency isolating transformer, reduced output voltage ripple due to three pulsed output current and the presence of only three actives switches connected at the same reference, this being a main advantage of this converter. By means of a specific switch modulation, the converter allows two operational regions. A Fuzzy logic control strategy is applied to input-current and output- voltage regulation. The chosen controller algorithm is a PI-like fuzzy control based on the error and change of error of the reference signal. The Takagi-Sugeno inference process was choosen due to lower processing required to obtain the results. Theoretical expressions and simulations results are presented for a 6.8 kW prototype, operating in region R2 in continuous conduction mode.

Efficiency optimization of DC/DC boost converter applied to the photovoltaic system

This work has as objective to maximize the efficiency of the DC/DC boost converter, used to track the maximum power of a PV system implemented by three panels, connected in series, with a total power of 600 W. The maximization is based on the selection of the magnetic material and of the operating point (Δi @ fs) that results in the best weighted average efficiency. Losses in the capacitors, semiconductors and magnetic devices are considered. Experimental results are presented to validate the simulated results obtained, as well as results of the efficiency of the boost converter. There different points will be presented to prove that operating point selected is the best among them.

Reduced order model of the boost converter with voltage multiplier cell

The boost converter with voltage multiplier cell allows the extension of static gain by means of the switching capacitor technique, reducing the duty cycle needed to achieve the same voltage gain when compared to the conventional boost converter. However, the modeling of this converter is complex and requires the use of advanced techniques due to the resonant inductor. For this reason, the dynamic model of this converter is still unpublished in the literature. This paper aims to present a reduced order model of this converter, without the resonant energy exchange between the capacitors, so that one can apply the state-space averaging technique assuming small ripple in the state variables. Extensive analysis demonstrates that the proposed modeling, although simplified, is sufficient for an adequate control system design for the converter.