中文摘要：

呈现负阻尼特性的恒功率负荷与分布式电源接入变换器级联容易导致系统出现振荡,给直流微电网稳定运行带来隐患.通过建立带恒功率负荷变换器在平衡点的小信号模型,推导变换器占空比与母线电压的传递函数,并从理论上分析传统PI控制器不能提高系统稳定性的原因,进而提出一种提高直流微电网母线电压稳定性的新型控制策略.通过绘制闭环系统的根轨迹图,分析控制器各参数的变化对系统稳定性的影响.以两源两负荷的直流微电网为例,建立MATLAB/Simulink仿真模型,仿真结果表明孤岛和并网运行下采用所提控制策略均可以保证直流微电网稳定运行.

英文摘要：

When constant power load with negative impedance characteristics and distributed power sources are integrated into a DC microgrid via converters,oscillation may easily＇ occur,causing the system stability problem. A small signal model of the converter with constant power load at the equilibrium point is established and the transfer function of converter between duty ratio and bus voltage is deduced. The reason that the traditional P[ controller cannot improve system stability is theoretically analyzed and a control strategy is proposed for DC microgrid to improve its bus voltage stability. The root locus chart of a closed-loop system is drawn and the impact of converter parameter variation on the system stability is analyzed. The simulation model of a two-generator two-load DC microgrid is built with MATLAB/Simulink and the simulative results show that,the stability of DC microgrid can be guaranteed by the proposed control strategy under both island and grid-connection operations.