A robust controller for a grid-tied inverter connected through an LCL filter

JUAN M. GONZALEZ; CLAUDIO A. BUSADA; JORGE A. SOLSONA

IEEE Journal of Emerging and Selected Topics in Industrial Electronics

IEEE

Lugar: Piscataway; Año: 2021 vol. 2 p. 82 - 89

2687-9735

This paper presents a control strategy for threephase inverters connected to grids through an LCL output filter. For this topology, it is known that when output current and capacitor current are fed back through certain optimal gains, the system is unfailingly unstable for a grid inductance value called ?critical?. For the critical inductance value, the system?sresonance frequency is equal to a sixth of the sampling frequency.In this paper, it is first checked that capacitor voltage positive feedback can stabilize this system. In addition, it is found that there exists a proportional relationship between the common coupling point voltage and the capacitor voltage. Based on this relationship, it is proposed to add grid voltage feedforward instead of capacitor voltage feedback for obtaining a stable system for every grid inductance value, including the critical value.In order to validate our assertion, this control law is tested via simulations and also, experiments on a prototype are included. Simulation and experimental results show the good performance of the proposed scheme.