Current distortion improvement and dc-link voltage regulation for bi-directional inverter in dc-microgrid applications

For dc-microgrid applications, a power supply system requires a bi-directional inverter to control the power flow between dc bus and ac grid, and to regulate the dc bus to a certain range of voltages. Its microcontroller has to determine operational modes and current commands for the inverter cycle by cycle. For using the memory space of the microcontroller efficiently and increasing current-command resolution, the controller uses a 2ⁿ approach. Moreover, we propose two modified switching operations, of which one can compensate the current distortion occurring near the zero crossing in rectification mode, and the other can reduce current distortion, especially under light load condition, by sampling inductor current only once at each switching period. Simulated and experimental results obtained from the proposed bi-directional inverter have verified the analysis and discussion.