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Introduction. This paper introduces a new method of islanding detection for distributed energy generation systems. Objective. To demonstrate that, with the method proposed, it is possible to achieve detection time measurements within the security margins defined by the regulations. Materials and methods. The method was implemented on a 230 W inverter. This method is based on the introduction of a disturbance at the inverter's output and the subsequent observation of the tension in the common coupling point (CCP), which depends on the impedance connected to the latter, in an islanding situation. The islanding detection is based on the Fourier's analysis. Results. Simulation and experimental results are provided, under several load and net conditions, achieving, in all cases, adequate detection times, not affecting the inverter's performance in terms of harmonic distortion or reactive power. Conclusions. The method proposed, if compared to others based on the injection of harmonics, can detect the islanding situation by the use of the Fourier's analysis applied to a unique harmonic, with no degradation of the power quality and within the time periods defined by the regulations. [ABSTRACT FROM AUTHOR]

An analysis of the conmutation processes in different modes of operation (inductive, capacitive and resistive) of the paralell-resonant inverters is presented in this paper. First the ideal and real behaviours of its semiconductor components are considered and the iddle components are excluded. Also the modes of operation corresponding to the proper MOSFET transistors trigger angle are analyzed. Second, the case in which the value of idle inductances of the circuit cannot be neglectable is considered, analysing also why are not commendable in this conditions the common conmutation strategies. A calculation strategy for proper moment of the transistors' triggering which provides a sure opperation in any working instant of the inverter circuit in optimum commutation mode is verified. Several simmulations that confirms the results validity using ORCAD software, are performed. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the sigma-delta conversion applied to the control of the DC link resonant inverters. This inverter configuration is often employed as a part of photovoltaic system because it presents the advantage that the semiconductors elements commute at zero tension or zero current. It happen on the high frequency elements and the inverter elements, and it is not necessary to modulate the DC tension, condition that simplified the control loop. Conversion analog-digital is an important step of the almost every modern electronics systems. After the signal is translated to the digital format, it can be processed easily in order to obtain the required information. [ABSTRACT FROM AUTHOR]