Contribuições na estratégia de controle por modos deslizantes aplicados a conversores formadores de rede

Abstract

Distributed generation systems, which use renewable energy sources, are increasingly presente in the electrical system due to the need to meet energy demand and environmental restrictions. Generally, such generation systems are connected to the electrical grid by means of power converters and, their integration into it, can produce instability in the electrical system. With the advancement in power electronics and the wide range of applications involving single-phase voltage converters, it is possible, with the appropriate control strategy, to dodge instability problems and offer improvements in the quality of the supplied power. For this, several control techniques have been studied for this purpose, however, the conventional techniques fail for not having robustness for parametric uncertainties and are dependent on the system model. Thus, the control by sliding modes has gained space in the control of converters because it is a robust technique to parametric uncertainties and is independent of the system model. Still, the chattering presence in the controlled variable in steady-state is its main disadvantage. In this sense, this dissertation presents a sliding mode control strategy applied to single-phase gridforming converters. The proposed strategy employs linear systems analytical tools in conjunction with equivalent control theory to determine the of closed-loop poles’ suitable location when constrained to the splip surface. Furthermore, a simplified structure is used to limit the maximum amplitude of the current passing through the converter switches. To emulate inertia and ensure power control of the converter, a power loop is implemented using the synchronous power control strategy. Simulation results obtained from a single-phase VSI connected to the grid operating under different operational conditions demonstrate the effectiveness of the proposed solution.