The main objective of this research is to propose an active and reactive power injection control in order to mitigate voltage sags. The proposed control strategy works in conjunction with a modified version of an automatic voltage regulator (AVR), where it will act on the active and reactive powers injected by the inverter to reduce the effects of voltage sags. In this way, the control will avoid possible shutdowns and damage to the equipment connected to the grid. The voltage improvement can be perceived for consumers connected to the power system. Modifications in AVR model and parameters are performed to speed up its performance, thus identifying the short-duration voltage variations (SDVV) and, consequently, the control acts to alter the powers, decreasing the active power injection and increasing the reactive power based on inverter capacity during the momentary voltage dip (MVD). Finally, when the fault is cleared, all values return to the pre-fault condition, so that the inverter only operates with active power. A 75 kW three-phase grid-connected photovoltaic system (GCPVS) equipped with the proposed control was inserted in a distribution grid of the city of Palmas, state of Tocantins, Brazil, and all of the computer simulations were performed on the Matlab/Simulink®.

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Abstract. This paper aims to present a preliminary study of the behavior of a distribution network with the penetration of grid-connected photovoltaic (PV) system. The work used measurements and data from an area of Palmas, the capital of Tocantins state, Brazil, which is attended by the power utility CELTINS. Three cases were analyzed here: (1) at a given daytime with the original distribution system, (2) at the same time with part of the distribution grid supplied by grid-connected PV systems, and (3) at a given nighttime. All the simulations were performed with PSAT software.

Resumo -Neste artigo, um condicionador de potência de quatro fios é proposto para conectar os painéis fotovoltaicos à rede elétrica. Este condicionador visa injetar potência ativa na rede e, ao mesmo tempo, melhorar a qualidade da energia quando há cargas desequilibradas e não lineares no sistema elétrico. Assim, são realizadas simulações computacionais para uma rede elétrica composta por dois sistemas fotovoltaicos conectados a um sistema elétrico e um conjunto de cargas com características desequilibradas, harmônicas e lineares. Inicialmente, os dois sistemas fotovoltaicos são conectados à rede por meio de inversores trifásicos. Em seguida, um dos inversores é substituído pelo condicionador de potência proposto. Com este estudo, constatou-se que o condicionador de potência proposto utilizado para conectar a geração fotovoltaica à rede elétrica contribui significativamente para suprimir correntes harmônicas e desequilibradas, trazendo melhorias significativas na qualidade de energia do sistema elétrico analisado.Palavras-Chave -Carga desequilibrada, Carga não linear, Condicionador de potência, Qualidade da energia, Sistema fotovoltaico.