An automatic voltage compensation technique for three-phase stand-alone inverter to serve unbalanced or nonlinear load

In this paper, a three-phase inverter providing automatic voltage compensation for unbalanced or nonlinear load under stand-alone operation is presented. An ideal load-side inverter should provide constant amplitude, frequency, and sinusoidal voltage at point of common coupling (PCC). Without stiff sinusoidal voltage support by grid, voltage quality at PCC is heavily affected by the type of load. To maintain voltage quality at certain level, a proportional-resonant (PR) controller embedded with automatic harmonic compensation scheme is proposed. Using the fast Fourier transform (FFT), dominant harmonic component could be identified for the PR controller to make voltage compensation at specific resonant frequency. The effectiveness of proposed control strategy is verified through experiments on a testbed of the three-phase stand-alone system.