Microinverters for photovoltaic (PV) modules can improve the energy generation by reducing the effects of shading, since the energy harvesting of each PV module can be controlled individually. In this context, this paper presents a topology of single-stage transformerless grid-connected boost microinverter. It promotes high voltage gain without using a preregulator circuit or a high/low-frequency transformer. A 500 W laboratory prototype was implemented and experimental tests were carried out so that the proposed microinverter was evaluated in a grid-connected PV system. Experimental analysis was performed in order to corroborate the theoretical approach and to verify the effectiveness of the proposed modified Perturb and Observe “Gama” maximum power point tracking technique and the proportional-resonant (P-Res) grid current controller under different irradiation conditions and under partial shading.

In many research centers around the world, had been researched models that accurately represent the PV modules operation. In this context, this paper presents a modeling of photovoltaic modules, which aims to simplify the simulation of photovoltaic systems in MATLAB ^® /Simulink. The model in question has not been very explored in the literature and, therefore, this paper has the purpose of evaluating its results connecting the model to a boost converter, being its main function the Maximum Power Point Tracking applying one of the most known methods, the P&O (Perturb & Observe). Furthermore, this converter elevates the voltage generated by the photovoltaic modules, in order to connect the PV array to the grid through an inverter. This paper also presents a good correlation between the theoretical and practical results from the modeling of the photovoltaic cell, and was observed a high efficiency of the implemented MPPT algorithm.

In photovoltaic power plants, fault diagnosis tools are essential for ensuring a high energy yield. These tools should be capable of accurately identifying and quantifying the factors behind the various fault mechanisms commonly found in photovoltaic plants. Considering the aforementioned factors, this article proposes an online smart PV monitoring solution, which is capable of detecting malfunctions that arise from accidental and/or technical causes through the analysis of I-V curves, however, without the necessity to interrupt the operation of the system, thus reducing the maintenance cost. Accidental causes can lead to the reduction of energy productivity due to the excessive accumulation of dirt on the photovoltaic modules, partial shading and eventual errors that occur during its installation. On the other hand, technical causes can be attributed to faults found on the photovoltaic modules, which lead to gradual losses in their electric and material characteristics. Therefore, by using the electric characteristics supplied by the manufacturer of the installed modules, the I-V and P-V curves of the operational photovoltaic strings were obtained in real time, compared to the respective theoretical curves obtained through mathematical modeling. In order to validate the proposed online monitoring system and its potential for predictive maintenance application, a field experimentation was mounted in a 93.8 kWp photovoltaic system.

This paper addresses the computational implementation and the comparative analysis of three Phase-Locked Loop (PLL) methods: Classic, TD-PLL (QSG group) and SOGI-PLL (AF group). These methods are used in Distributed Generation (DG), composing Microgrids and Smart Grids, for synchronization and monitoring. They are extremely important for integrating these systems into the power grid and, therefore, they must comply with standards such as IEEE 1547 and ABNT NBR 16149. These standards impose frequency and voltage variation limits in order to connect the DG systems to the low-voltage power system. For verifying the correct operation of the PLLs under different grid conditions, computational results about the performance of each one are presented. Both ideal and highly distorted grids are considered to analyze the behavior of each PLL method under variations of frequency, phase angle and voltage amplitude. The evaluation criteria are: frequency oscillation, settling time and phase error in steady state.