Control of Single-Phase Grid-Connected Inverters With Nonlinear Loads

This paper presents a control of single-phase grid-interactive inverters with nonlinear loads. The utility-connected inverter should operate at both stand-alone and grid-connected modes. However, the waveform qualities of the grid current in grid-connected mode and the output voltage in stand-alone mode are poor under the nonlinear critical load with the conventional control. The impact of the nonlinear load on the grid current is analyzed. The proposed control is illustrated in detail. By adding the load current into the filter inductor current loop, the influence of the nonlinear load on the grid current can be eliminated, and the waveform quality of the output voltage in stand-alone mode can be improved. The control method is simple and easy to be achieved. The grid-connected inverter is stable at both modes. The filter inductor is chosen. Simulation and experimental results from a 1-kW dual-buck full-bridge grid-interactive inverter with a diode rectifier load verify the theoretical analysis.