Abstract: As an effective supplement for smart energy in Internet, Microgrid (MG) could realize the frequency and voltage supporting functions and allocate the load power automatically when it runs in the island mode. As the Virtual Synchronous Generator (VSG) control with drooping feature can realize the automatic power distribution of the inverter according to the design parameters due to its inertia and damping links. However, due to the differences and changes in the impedance of the inverter connection lines in the microgrid, the VSG cannot only rely on the designed droop parameters to achieve the sharing of reactive power in full work conditions. Therefore, an improved reactive-voltage control method of VSG based on short-time pulse injection line impedance identification is proposed. The line voltage drop generated by each inverter is compensated by identifying the line impedance in advance, and a parallel inverter is realized common bus voltage-reactive droop control to compensate for the impact of line impedance voltage drop on the rational distribution of reactive power. The principle and implementation of the improved reactive power control under the control of VSG are analyzed, and the effectiveness of the method is verified by some simulations.

Key words: Microgrid, parallel-inverter; VSG, reactive power sharing, line impedance identification

摘要： 微电网作为“互联网+”智慧能源的重要补充，要求其在孤岛运行时，能够实现电压、频率有效支撑及负荷功率自动分配的功能。具有下垂特性的虚拟同步机(Virtual Synchronous Generator，VSG)控制由于具有惯性和阻尼环节，能够依据设计参数实现逆变器的功率自动分配，但由于微网内各逆变器连接线路阻抗的差异与变化，使得虚拟同步机控制无法仅依赖确定的下垂参数实现无功功率全工况均分。为此，提出一种改进的基于短时脉冲注入线路阻抗辨识的虚拟同步机无功-电压控制方法，通过预先辨识线路阻抗来补偿各逆变器产生的线路压降，实现了并联逆变器公共母线电压-无功下垂控制，以此来弥补线路阻抗压降对无功功率合理分配的影响。并对虚拟同步机控制下改进的无功控制原理及实现方案进行了分析，并通过仿真验证了方法的有效性。

关键词: 微电网, 并联逆变器, 虚拟同步机, 无功均分, 线路阻抗辨识