中文摘要：

下垂控制逆变器并联系统中虚拟负阻抗技术是一种有效实现功率均分与环流抑制的手段，虚拟阻抗大小影响其实现效果及系统稳定性。建立了逆变器并联系统的下垂控制小信号模型，利用根轨迹图设计下垂系数并确定等效输出阻抗范围，进而从系统稳定性需求出发分析了虚拟负阻抗与环流的联系和虚拟负阻抗的设计。仿真和实验结果表明，所设计的逆变器并联系统稳定，且能有效实现逆变器功率均分和环流抑制。

英文摘要：

Virtual negative resistance technique for inverter parallel system with droop control is an effective means to achieve power sharing and circulation inhibition, in which virtual output impedance determines the effectiveness and the stability of the system.The small signal model of droop control for parallel inverter system is built, and then the droop coefficients are designed and the equivalent output impedance ranges are determined by using root locus.According to the requirement of system stability, the relationship between virtual negative impedance and the circulating current is analyzed and the virtual negative impedances are designed.The simulation and experimental results show that the in- verter parallel system is stable and effectively implements the power sharing and the circulating current suppression.