An "ac Inductor" Based Grid Connected Inverter

This study proposes a soft switched Output Current Sourcing (OCS) grid connected inverter that applies a high frequency isolation transformer. Current sourcing at the output implies that, ideally, the injected current will be independent on the load voltage. The current injected to the line is controlled by varying the switching frequency and dithering at low currents. The system does not require the sensing of the output current or even the line voltage except for synchronization. This is in contrast to the conventional voltage sourcing inverters where the small disturbance at the line voltage may lead to current run away and consequently a tight current feedback loop must be applied. The proposed topology and several proposed control approaches were analyzed and verified by simulations and by experiments. The simulation and experimental results confirm the theoretical analysis and show that the proposed inverter can be operated with no sensing of the line current or voltage.