Contribuições para algoritmos de sincronização de conversores estáticos conectados à rede elétrica.

Abstract

Normally, for equipments connected to the grid such as power converters, active Ąlters, controlled rectiĄers and others, phase locked loop (PLL) algorithms are used to obtain synchronization between the electric grid and equipment. However, these PLL algorithms often present unsatisfactory dynamic response when the electrical grid presents distortions such as harmonics and phase steps. In this work, it is discussed performance improvements in phase and frequency tracking for PLL algorithms. It is proposed the use of an adaptive delay bank Ąlter (ADB Ąlter) to solve the problem of square wave PLL (PLLOQ) phase error, when the grid presents harmonic components. Through simulation and experimental tests, it was veriĄed that the phase error caused by harmonics can be eliminated. However, the error correction introduced a delay of 10ms in PLLOQ dynamics. Nevertheless, this PLL was competitive when compared to other structures, for example, those that use adaptive notch Ąlter. Next, it is proposed to use the ideal resonant proportional (PR) controller in PLL structures. A systematic method for designing the control parameters of a PLL using the PR controller is presented. Performance comparisons of the classical PLL using the proportional integral (PI) controller versus PR controller are presented by means of simulation and experimental results, where it was veriĄed that the PLL with the PR controller obtained a faster response in the phase and frequency detection. It was also veriĄed, a good precision (null error in steady state) in the detection of the parameters of interest, besides obtaining satisfactory results (it tracked phase and frequency) when the grid presented distortions. Subsequently, the performances of the following PLLs are compared: (1) PLL based on the Park Inverse Transformation (Park-PLL) using the PI

and PR controllers, (2) PLL based on the Generalized Second Order Integrator (SOGI- PLL) using the PI controller and (3) Enhanced Phase Locked Loop (EPLL) with PI

controller. Through the analyzes, for diferent grid scenarios, it was veriĄed that the best performance among these algorithms was that of the SOGI-PLL with PI controller. The Park-PLL with PR controller obtained the fastest phase detection, while the EPLL with PI controller obtained the slowest phase detector. Furthermore, it was observed that these algorithms obtained null error in steady state, except when the grid presented harmonics. Finally, a general analysis of the main results obtained in this work was carried out, where the best PLL choices for speciĄc applications were indicated.