An Enhanced Power Decoupling Control for Grid-connected Capacitive-Coupling Inverters

Capacitive-coupling inverter (CCI) has low operation voltage and wide reactive power control range characteristics. Hence, it is a promising solution for parallel-connected inverters in microgrids (MGs). Decoupling control is popular in local controllers since it is able to adjust power transfer automatically as per demands varies. However, the conventional decoupling control cannot fully utilize CCI's power control capability, due to the decouple effect is limited by a small maximum phase angle. A virtual-impedance loop therefore is investigated to release the potential of CCI's power transfer. The proposed control is advantageous that the goal can be achieved by varying the equivalent impedance via programming, without making any changes in the real hardware. To ensure the desirable power delivery effect, transit response and stability are also studied. Simulation and experimental results are provided to show the validity of the proposed control method.