在能源需求和环境保护的双重压力下，充分利用新能源发电的微电网受到了越来越多的关注。其中下垂控制作为微电网中重要的控制策略，可以提高微电网在孤岛和并网运行时的稳定性、安全性、可靠性。但是该控制策略仍然会受到不同线路阻抗特性及谐波的干扰，并且会造成母线电压产生偏差。本课题主要对低压微电网中传统下垂控制策略的不足进行改进。 针对低压微电网中传统下垂控制的分布式电源输出功率耦合的问题，在dq坐标系下建立了下垂控制的逆变器数学模型，结合分布式电源功率传输特性和下垂曲线的综合分析结果，在该控制策略中加入了虚拟阻抗。同时分析了虚拟阻抗控制环对系统输出特性的影响，设计了该控制策略的电压电流双环控制器和虚拟阻抗下垂控制模型，并且在MATLAB/Simulink中建立了微电网模型，验证了改进下垂控制方法的有效性。 由于微电网中大量电力电子器件和非线性负荷的存在，会使分布式电源输出电压受到谐波的影响，在虚拟阻抗环中加入了二阶广义积分器来抑制谐波，并建立了基于二阶广义积分虚拟阻抗的下垂控制模型。通过对微电网孤网和并网运行时的谐波抑制效果进行仿真研究，结果表明该方法均可有效的抑制谐波，并且虚拟阻抗的取值越大其谐波抑制的能力越好。 针对虚拟阻抗下垂控制策略在使用过程中引起的母线电压偏差会导致系统电压过低的问题，在基于二阶广义积分虚拟阻抗下垂控制的基础上，加入了电压偏差实时计算补偿环节。通过对该电压补偿方法进行仿真研究，结果表明微电网在整个运行过程中母线电压均可保持在额定值，从而避免了母线电压偏差对微电网系统的不利影响。

Under the dual pressures of energy demand and environmental protection,the micro-grid that makes full use of new energy to generate electricity has received more and more attention. Droop control is an important control strategy in micro-grid. It can improve the stability, safety and reliability of the micro-grid during islanding and grid-connected operation.However, this control strategy is still subject to interference from different line impedance characteristics and harmonics, and will cause deviations in the bus voltage. This topic is mainly aimed at improving the shortcomings of traditional droop control strategies in low-voltage micro-grids. For the problem of distributed generation output coupling of traditional droop control in low voltage micro-grid,a mathematical model of the inverter with droop control is established in the dq coordinate system.Combined with the comprehensive analysis results of the distributed generation transmission characteristics and the droop curve, a virtual impedance is added to the control strategy.At the same time, the influence of the virtual impedance control loop on the output characteristics of the system is analyzed. The voltage-current dual-loop controller and the virtual impedance droop control model of the control strategy are designed. And the micro-grid model was established in MATLAB/Simulink to verify the effectiveness of the improved droop control method.. Due to the existence of a large number of power electronic devices and non-linear loads in the micro-grid, the distributed generation output voltage is affected by harmonics. A second-order generalized integrator is added to the virtual impedance loop to suppress harmonics. And the droop control model based on second-order generalized integral virtual impedance is established.The simulation results of the micro-grid isolated and grid-connected harmonic suppression are carried out. The results show that the method can effectively suppress harmonics, and the larger the value of virtual impedance, the better the harmonic suppression ability. For problem of the bus voltage deviation caused by the virtual impedance droop control strategy during use, the system voltage is too low. Based on the second-order generalized integral virtual impedance droop control, the voltage deviation real-time calculation compensation link is added. Through the simulation study of the voltage compensation method, the results show that the bus voltage can be kept at the rated value during the whole operation of the micro-grid, thus avoiding the adverse effect of the bus voltage deviation on the micro-grid system.