Modeling and Application of Controllers for a Photovoltaic Inverter for Operation in a Microgrid

Abstract

The penetration of renewable energies in the context of distributed generation represents challenges such as maintaining the reliability and stability of the system and considering the random behavior proper of generation and consumption. In this context, microgrids make it possible to manage effectively the generation and consumption of this energy, incorporating, electronic power converters, energy storage systems, and hierarchical control schemes. This paper presents the modeling, design, and application of controllers for a photovoltaic inverter operating in island mode. For this application, the photovoltaic inverter regulates the inverter output voltage via two control configurations implemented to follow the voltage reference imposed by the scheme droop. The first control scheme is configured with a two-degrees-of-freedom controller plus a repetitive controller. In this configuration, the repetitive controller is implemented in the direct loop. The second scheme is configured with an integral proportional controller—proportional controller plus a resonant controller. This configuration is formed by an integral proportional control in the direct loop plus a resonant controller and a proportional controller in the feedback loop. Both control configurations are implemented to improve the inverter disturbance rejection capability when it feeds both linear and non-linear local loads. In addition, these configurations allow the parallel connection of inverters with good performance, using a droop scheme that allows the parallel connection of converters. The tests are carried out by means of simulations using PSIMTM, which shows that, with the implemented controllers, the total harmonic distortion of the inverter output is below 5%, as recommended by the IEEE 519-1992 standard.