基于虚拟同步机的微网逆变器建模与控制技术研究

发布时间：2018-11-25 22:35

【摘要】：随着电力需求的增加和分布式发电技术的发展,统一协同管理和调度分布式电源,既能在孤岛情况下对一定范围内负荷进行供电,又与电网进行功率交换的微网技术得到了广泛应用,实现了大规模分布式电源接入电网,但随着微网规模的不断扩大,加上分布式电源渗透率的不断提高,使传统微网在集中调度方式,如主从控制,分层控制下出现了调度成本增加,系统拓扑结构拓展困难等问题,不利于分布式电源的高效利用,且由于分布式电源多以电力电子逆变器的形式接入微网系统,响应速度较快,外特性较硬,难以为微网系统带来如同步电机固有的旋转惯性,导致系统易振荡,整体稳定性不高。本文在微网逆变器控制上采用了虚拟同步机方法,在实现微网分布式控制的同时,通过模拟同步电机转子运动方程进行控制器设计,产生与同步电机相似的外特性,提高系统整体惯性。与现有方法相比,本文基于多环控制实现,外环加入虚拟惯性实现分布式频率电压调节,内环实现输出电压无差调节并提高电流动态响应;设计了改进的基于虚拟磁链的矢量定向方法,应用于dq坐标系下控制及并网预同步过程,实现了输出电压对于电网电压的无差跟踪以及孤岛、并网模式的平滑切换;设计了基于模糊控制器的虚拟惯性时间常数自适应调节机制,为虚拟同步机提供了较宽的惯性带宽,抑制微网振荡引起的频率波动,并在负荷投切和分布式电源接入时展现出更好的动态特性。文章提出的虚拟同步机多环控制结构、并网策略及参数自适应调节方法,均在Matlab/simulink平台下搭建仿真模型,并进行了算例分析,实验结果与现有方法进行了对比,证明了提出方法的有效性,展现了控制性能的提升,对于分布式电源大规模利用和微网与电网侧的功率交互都有一定参考价值。
[Abstract]:With the increase of power demand and the development of distributed generation technology, unified cooperative management and dispatch of distributed power supply can supply power to a certain range of loads in isolated island. The microgrid technology of power exchange with the power grid has been widely used to realize large-scale distributed power generation access to the grid, but with the continuous expansion of the microgrid scale and the increasing permeability of distributed power generation, The traditional microgrid has some problems such as the increase of scheduling cost and the difficulty of expanding the system topology under centralized scheduling, such as master-slave control, hierarchical control, and so on, which is not conducive to the efficient utilization of distributed power. Because the distributed power supply is connected to the microgrid system in the form of power electronic inverter, the response speed is fast and the external characteristic is hard, so it is difficult to bring the rotating inertia of the synchronous motor to the microgrid system, which leads to the system oscillation easily. The overall stability is not high. In this paper, the method of virtual synchronous machine is used in the control of microgrid inverter. The controller is designed by simulating the motion equation of the rotor of synchronous motor while realizing the distributed control of microgrid, which produces the external characteristics similar to that of the synchronous motor. Improve the overall inertia of the system. Compared with the existing methods, this paper realizes the distributed frequency and voltage regulation based on the multi-loop control, the outer loop adds virtual inertia, and the inner loop realizes the output voltage adjustment without difference and improves the dynamic response of the current. An improved vector orientation method based on virtual flux linkage is designed, which is applied to the process of control and grid-connected pre-synchronization in dq coordinate system. The output voltage is tracked without difference to the grid voltage, and the smooth switching of islanding and grid-connected mode is realized. An adaptive control mechanism of virtual inertial time constant based on fuzzy controller is designed, which provides a wide inertial bandwidth for the virtual synchronous machine and suppresses the frequency fluctuation caused by the microgrid oscillation. And show better dynamic characteristics in load switching and distributed power access. In this paper, the virtual synchronous machine multi-loop control structure, grid-connected strategy and parameter adaptive adjustment method are all built under the Matlab/simulink platform, and an example is given. The experimental results are compared with the existing methods. It is proved that the proposed method is effective and the control performance is improved. It has some reference value for large-scale utilization of distributed power generation and power interaction between microgrid and power grid side.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM727

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