The line impedance is resistive in low voltage microgrids. In order to ensure that the output impedance matches the line impedance， virtual impedance is introduced to the control strategy for inverters. The impact of integral coefficient voltage loop on output impedance is analyzed. The improvement of voltage loop integral coefficient can make the output impedance become resistive provided that the inverter is in a stable operation state. From the analysis on equivalent circuit of a low voltage microgrid， it is concluded that the active power and reactive power can be changed by adjusting the output voltage amplitude and frequency of the inverter respectively. The impact of parameter examination error on output power of the power inverter is analyzed. The amplitude and frequency proportional-integral（PI） regulators are introduced to droop control strategy， which can realize zero-error tracking of the output power. The simulation results verify that the performance of the proposed control strategy is excellent both in grid-connected mode and islanded mode.