Virtual negative impedance droop method for parallel inverters in microgrids

Most microgrid converters are controlled by droop method, which could ensure microgrid converter to realize load distribution under low-speed communication. Because the microgrid line impedance is resistive, which makes the output active power and reactive power coupling each other and reduces the stability of microgrid. Introducing virtual impedance can adapt droop control for resistive lines. However, virtual impedance may lead to great voltage drop and harmonic amplification. The traditional droop control strategy were analyzed, and a droop control strategy based on voltage and current double-loop for multi-inverters parallel operation in microgrid was proposed by introduction of virtual negative resistance . By offsetting part of line resistance by the virtual negative resistance, equivalent performance can be achieved with smaller virtual impedance, which improves voltage quality. Matlab simulation confirms the effectiveness of the proposed method.