Research On Single-Phase Grid Connected Inverter Based On Coordinate Transform With No Delay Time

With the progress of renewable-energy generating, some converted energy need to be sent to grid by inverter. In the distributed generating system, the stability and reliability of the grid-connected inverter needs to be protected. In this paper, it bases on a novel control technology of grid-inverter and its phase locked loop which mainly refers to single-phase inverter.It analyzes the current control of grid-connected inverter and especially on the synchronous rotation coordinate transform of three-phase inverter. Considering the complexity of the synchronous rotation coordinate transform and delay time when the single-phase inverter uses it, a novel control technology of grid-inverter and its phase locked loop and mainly refers to single-phase inverter is presented.Through the transformation, the conventional PI controller is changed to the PR controller which can get zero steady error to the AC signal.The phase locked loop is necessary to the grid-connected inverter. Based on the conventional PLL, an enhanced phase locked loop (EPLL) is used which is a amplitude-frequency PLL. It not only follows the frequency of input signal but also the amplitude. To the worst case of grid when it is distorted or contaminated by the harmonics, the performance of the EPLL is excellent.At last, experiment is done based on a single-phase full bridge main circuit and it uses the novel control. The experimental results verify that the novel control is effective.