High step-up conversion is an indispensable feature for the power processing of low voltage renewable sources in grid-connected systems. Motivated by this necessity, this paper presents a study on non-isolated dc-dc converters based on the conventional Boost converter that can provide such feature with high efficiency. By the topological variation and gain cell concepts, it is demonstrated that these converters can be treated as a unique generalized converter, called Boost Converter with Gain Cell (BCGC). The operating principle, the key waveforms and the components stresses of the BGCG are analyzed for the continuous-conduction mode, independently of the employed gain cell. A methodology to create the gain cells is developed from the combination of coupled inductors and voltage multiplier techniques. In order to verify the realized analysis, a 150 W prototype concerning to the proposed generalized converter and able to operate with several different gain cells is developed for the comparison between theoretical and experimental static gain results.

Due to the plethora of non-isolated high gain step-up dc-dc converters presented in the literature, it has become important to comprehensively review and classify them, as well as to derive methods to generalize the usage of the commonly employed techniques. Motivated by this need, this paper not only proposes a new family of high gain step up dc-dc converter, but a generalized methodology to derive them from any classical dc-dc topology by applying a coupled inductor and voltage multiplier cells. For illustrating the methodology, high gain dc-dc converters based on the basic topologies (Buck, Boost, and Buck-Boost) are developed and analyzed. These converters are compared in terms of voltage gain, coupled inductor size, voltage stresses, total device rating, switching frequency effect in power loss, and output power regulation. Moreover, in order to verify the proposal, two practical experimentations are accomplished. Firstly, a prototype able to operate as any of the three basic topologies with different gain cells is developed for comparing theoretical, simulated, and experimental static gain results. Secondly, well-designed prototypes concerning to the Buck-, Boost-, and Buck-Boost-based converters are assembled for efficiency evaluation.

Photovoltaic (PV) thin-film modules normally present higher voltages at the maximum power points (MPPs) than crystalline silicon ones. This feature makes the usage of low voltage MOSFETs (≤100V) unfeasible in high step-up Boost-based converters. In order to solve this drawback, this paper proposes a novel high step-up non-isolated dc-dc converter based on the classical synchronous Buck converter with coupled inductor and voltage multiplier techniques. Besides reducing the voltage stress on the active switches, the proposed converter also requires a coupled inductor with lower core-window product, allowing the use of a smaller magnetic device. The resonant operation mode of the proposed converter enables zero-voltage-switching (ZVS) turn-on of active switches and zero-current-switching (ZCS) turn-off of diodes, which increases its efficiency. A 150-W prototype, able to work with a large variety of commercial PV thinfilm modules, with 55-85-V input and 400-V output voltages, is built to verify the developed analysis. Experimental results show that the maximum obtained efficiency is nearly 98.0% and the weighted California Energy Commission (CEC) efficiencies are greater than 96.7% over the whole input voltage range.

The I-V curve tracer is an instrument that captures the current-voltage characteristics of photovoltaic (PV) generators under real operating conditions. Such device can be used to evaluate their performance and identify faults or aging effects, but its high costs have prevented it from being widely used in the industry. This article thus proposes the design of a low-cost, portable I-V curve tracer based on the classic dc-dc Ćuk converter for PV modules of up to 300 W. In order to obtain a compact device, some design techniques are proposed, including circuit reduction, high switching frequency operation, specification of the optimum load resistor power rating, and improved measurement distribution because of a nonlinear duty cycle variation. Experimental curves were compared with those acquired from commercial PV tracers to demonstrate its accuracy. In addition, the physical parameters of the well-known single-diode model have been extracted and compared with data provided by manufacturers to identify aging effects and module performance.

A novel high step-up high efficiency DC-DC converter for photovoltaic energy conversion is presented in this paper. The proposed converter employs a coupled inductor and two voltage multiplier cells to achieve high step-up voltage gain. The operating principle and the steady-state analyses of voltage gain are described in detail. A 200 W prototype with 20-30 V input and 400 V output voltages is built to verify the analysis. The maximum efficiency of the prototype is nearly 97.7% and the efficiency is higher than 97% over a wide load range.

In this work a grid-connected renewable energy system composed by a lkW photovoltaic (PV) array and a 1 kW wind turbine (WT) is presented. The generated power from each renewable source is processed by independent dc-dc converters and provided to a common dc bus. Once batteries employment is not desired, a 1.2 kW fuel cell (FC) and a supercapacitor bank (SCB) are used as backup, in order to keep a dc critical load continuously supplied. The SCB operates as a short term storage device and its use also ensure the 120 Hz voltage ripple attenuation. From proper process, the dc bus power is delivered to the main grid with high power factor. This paper presents all theoretical analysis referring the proposed system, including the MPPT strategies for PV and WT generators and the control strategies for the system operation on grid-connected and stand alone modes. A complete power flow study is also presented, considering several combinations of power generation and load demand. Simulation results, obtained by the use of PSIM software, are accomplished in order to validate the system operation.