微网是集于小型分布式发电和负荷为一体的微型电网。作为智能电网的重要组成部分，微网不仅是传统电网的有效补充和分布式电源的有效利用形式，同时还是大力发展可再生能源、提高供电电源可靠性、扩大供电系统容量的重要途径。 逆变器作为微网系统的核心组成部分，要求它能够输出高质量的电压波形。对逆变器的控制方法进行理论分析后，使用了电压、电流的双闭环控制系统，改善了逆变器动态响应慢、系统带宽控制能力弱等缺点，同时对控制系统和LC滤波器参数的选取进行了推导。通过对双环控制的逆变器及其输出波形的性能分析，表明该控制方法满足微网系统的要求。 微网的正常运行离不开高效稳定的控制系统。文章分析了P-Q、V/f、下垂（Droop）控制三种典型的微网控制策略，在控制原理的基础上给出了相应的控制流程。着重研究了微网中并联的分布式电源之间的功率均分问题和主从控制、对等控制方法。实现了单分布式电源和不同容量的多分布式电源在并网和孤岛模式下的稳定运行。 微网在并网运行和孤岛运行模式之间的平滑切换是提高微网系统供电可靠性的核心手段。针对孤岛运行时微网输出电压和电网电压之间的关系，利用PLL检测微电源和大电网的电压、相位后，通过下垂控制调节，使微源可以根据大电网调节自身的电压、相位、频率，实现了微网孤岛运行和并网运行之间的平滑切换。 考虑到建立微网实验系统的复杂性和局限性，以Matlab仿真软件为平台建立了微网数值仿真模型，分别对单微源并网运行及其孤岛运行、多微源并网运行及其孤岛运行和运行模式平滑切换进行了仿真分析，通过仿真实验结果，验证了所采取控制策略的正确性，对实际系统具有一定的指导意义。

Microgrid is a kind of power grid integrating part of small distributed power generations and local loads. As an important part of smart grid, microgrid is not only an effective complement of traditional grid but also an efficient form of using distributed power, besides, it is an important way to vigorously develop renewable energy sources, improve reliability of power supply, and expand power supply system capacity. As the core of the microgrid system, inverter is required to output high quality waveforms of voltage. After the control method of the inverter is theoretical analyzed, the outer voltage loop and internal current loop are used in the double closed loop control system, and the disadvantages of slow dynamic response and weak bandwidth control force of the inverter are improved, meanwhile, the parameters selection of the control system and LC filter are derived. According to the analysis of the dual-loop control inverter and output waveforms, it has been shown that the control method can meet the requirements of the microgrid system. An efficient and stable control system plays an great important role in normal operation of microgrid. In this paper, three kinds of typical control strategy of microgrid including P-Q, V/f, and Droop are analyzed, and the corresponding control process based on control theory is given. The power split problems in shunt-wound distributed power source, master-slave control, and peer-to-peer control method in microgrid. The single distributed power source and multi-distributed power source with different capacity are made to operation stably in the grid-connected mode and islanded mode. Smooth transition between grid-connected grid mode and islanding mode is the core means of microgrid system to enhance its reliability. According to the relationship between the output voltage and grid voltage when microgrid is operating in islanding mode, PLL is used to detect the micro power source, as well as voltage and phase of large power grid, the micro source can adjust the grid voltage, phase, frequency by means of droop control, the smooth transition between grid-connected grid mode and islanding mode smooth is achieved. Considering the complexity and limitations of establishing an microgrid experimental system, the microgrid simulation examples are established by using Matlab software, the single micro source and multi-micro source operating in both grid-connected grid mode and islanding mode as well as smooth mode transition are simulated and analyzed, and the microgrid operation characteristic waveforms are obtained, the simulation results conform to the theoretical research, verifying the correctness of the control strategy, which has certain guiding significance to practical application.