A novel control strategy for parallel-connected converters in low voltage microgrid

Droop control methods are usually used for the parallel operation of multi-converters in microgrid to avoid the dependence of communication system. However, the current sharing among the parallel-connected converters is affected due to the high resistive line impedance in low voltage microgrid system. Virtual impedance control was then presented to improve the load current sharing accuracy by the adjustment of the total equivalent output impedance between converters and AC bus. However, the virtual impedance control loop will cause large voltage reduction on inverters output voltage which may deteriorate microgrid voltage quality. In this paper, an amplitude correction method is proposed to improve the voltage reduction through the local information of the parallel-connected converters completely. Simulation results verify the effectiveness of the proposed strategy.