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This paper presents four different control design strategies for linear quadratic regulators applied to DC-DC boost converters operating under large load range, pointing out advantages and drawbacks by means of a performance comparison. Two of the strategies are based on single controllers and the other two use a set of local controllers to cope with the entire load range. The robust stability of the closed-loop linearized system with the four control strategies is investigated via the existence of a common Lyapunov function, obtained in a fast and efficient way by the solution of linear matrix inequality conditions.

Abstract-This paper presents a review and a comparative analysis between mathematical models for the efficiency of power converters. Two different types of models are considered, being one for converters subject solely for output power variations, and a second one also considering input voltage variations. Both cases are particularly important for systems fed by renewable sources as photovoltaic panels or wind turbines. Knowledge of the appropriate models is of interest in the development of high-performance systems, allowing one to optimize the global efficiency of the converter system. Experimental results concludes the comparison between the investigated models and a discussion of pros and cons of each model are presented, providing to authors a better choice for modeling the efficiency behavior of power converters.

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High step-up converters are required and used in photovoltaic applications, due to low voltage of photovoltaic modules. In this paper, an isolated dc-dc high step-up SEPIC with a Greinacher voltage doubler cell is presented. It has the advantage of continuous input current, high efficiency, high voltage gain, isolation and demands a single switch, being suitable for low power grid-tie photovoltaic systems. The operating principles and steady-state analysis are presented, including the detailed analysis of resonant stage, where the value of primary side capacitor is taken into account and plays an important role in the design of the converter, since it directly affects the resonance frequency and RMS current values. Simulation results are presented to validate the analysis and design.

Abstract-This paper proposes a new methodology for efficiency optimization in systems composed by parallel converters. The proposed methodology takes into account the individual efficiency curves and determines the optimum operating point for each converter such that the maximum efficiency of the arrangement is achieved for the entire load range. Due to the nonlinearity of the problem and the complexity of the solution hyperplane, the optimization process is divided into stages of global optimization, local optimization and ambiguity resolution. This latter verifies the existence of multiple global minima and selects the most appropriate in function of previous power distributions. Case studies demonstrates the validity of the proposed methodology for different systems configurations.

Generating sources of renewable systems, like photovoltaic module or fuel cell, have a low‐output voltage that has to be boosted for most of applications, such as grid‐tie inverters. To accomplish this, an isolated DC–DC high step‐up single‐ended primary‐inductor converter (SEPIC) with a Greinacher voltage doubler cell is presented. It has the advantage of continuous input current, high efficiency, and high‐voltage gain and isolation and demands a single switch, being suitable for low‐power grid‐tie photovoltaic systems. The operating principles and steady‐state analysis are presented, including the detailed analysis of resonant stage, and the effects of transformer winding capacitances on converter operation are investigated. Moreover, the effects of resonance frequency variations on converter efficiency are experimentally investigated. Experimental results on a 50 kHz and 200 W prototype are presented to validate the proposed concept.