微网孤岛与并网运行模式切换控制策略研究

发布时间：2018-04-16 12:00

本文选题：微网 + 光伏逆变器　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：微网作为高效利用可再生能源、提高供电可靠性和灵活性的有效方式，是解决当前环境污染、资源短缺等问题的新方法。微网的稳态运行包括孤岛和并网两种模式，二者的无缝切换是保证负载持续不间断供电、改善电能质量、提高供电灵活性和可靠性的关键，具有重要的研究意义。本文针对微网的模式切换控制策略展开研究，实现模式切换暂态过程平滑无冲击。设计了基于交流母线、以光伏为分布式电源的微网系统结构，选取了光伏逆变器的两级式拓扑结构，，设计了逆变器参数，并建立了其数学模型。分析了传统微网控制策略在模式切换时产生冲击的原因，并提出了微网系统新型整体控制策略，其中的光伏逆变器在孤岛运行、并网运行和模式切换过程中均采取基于下垂理论的电压型控制方法，避免了传统控制策略的强制切换，从根本上抑制暂态冲击的产生。提出了光伏逆变器的孤岛控制策略，针对本文微网系统低压电力线的阻抗的特点，采用适用于阻性情况下的下垂方程，保证有功功率和无功功率能够进行充分的解耦控制，在为整个系统建立稳定频率和电压的同时为负载可靠供电。提出了光伏逆变器电压型并网控制策略，对电压型控制逆变器的并网功率进行了分析，指出下垂控制可用于逆变器并网。在阻性下垂控制的基础上增加了功率环和直流母线电压环，解决了电压控制型逆变器并网功率易受电网波动影响等问题，增强了光伏逆变器对功率的控制能力，满足了始终以最大有功功率并网和维持直流母线电压稳定等要求。最后提出了模式切换控制策略，基于下垂理论实现了预同步功能，保证了切换过程的平滑过渡。搭建了系统的仿真模型，分别对所提出的控制策略进行了不同情况下仿真验证。调试完成了系统实验平台以进一步验证本文控制策略，实验结果表明逆变器能够分别稳定工作于孤岛运行模式和并网运行模式，并较好地实现了二者间的无缝切换，保证了切换过程的平滑无冲击和负载的连续供电。
[Abstract]:As an effective way to utilize renewable energy efficiently and improve the reliability and flexibility of power supply, microgrid is a new method to solve the problems of environmental pollution and resource shortage.The steady operation of microgrid consists of two modes: island and grid-connected. The seamless switching between them is the key to ensure the continuous uninterrupted power supply, improve the power quality, improve the flexibility and reliability of power supply, and has important research significance.In this paper, the mode switching control strategy of microgrid is studied, and the transient process of mode switching is smooth and impactless.The microgrid system structure based on AC bus and photovoltaic distributed power supply is designed. The two-stage topology structure of photovoltaic inverter is selected and the parameters of inverter are designed and its mathematical model is established.This paper analyzes the causes of the impact of the traditional microgrid control strategy in mode switching, and puts forward a new overall control strategy for the microgrid system, in which the photovoltaic inverter operates on an isolated island.Voltage mode control method based on droop theory is adopted in grid-connected operation and mode switching process, which avoids the forced switching of traditional control strategy and restrains the generation of transient impulse fundamentally.The islanding control strategy of photovoltaic inverter is proposed. According to the characteristics of the impedance of low-voltage power line in the micro-grid system, the droop equation suitable for resistive condition is adopted to ensure that the active power and reactive power can be fully decoupled.The stable frequency and voltage are established for the whole system while the load is supplied reliably.The voltage source grid-connected control strategy of photovoltaic inverter is proposed. The grid-connected power of voltage source control inverter is analyzed. It is pointed out that droop control can be used for grid-connected inverter.On the basis of resistive droop control, the power loop and DC bus voltage loop are added to solve the problem that the grid-connected power of the voltage controlled inverter is easily affected by the power fluctuation of the power grid, and the power control ability of the photovoltaic inverter is enhanced.It meets the requirements of grid connection with maximum active power and maintenance of DC bus voltage stability.Finally, the mode switching control strategy is proposed, and the presynchronization function is realized based on droop theory, which ensures the smooth transition of the switching process.The simulation model of the system is built, and the proposed control strategy is simulated under different conditions.The system experiment platform is completed to further verify the control strategy in this paper. The experimental results show that the inverter can work stably in island operation mode and grid-connected operation mode, and realize the seamless switching between them.Ensure smooth switching process without impact and load of continuous power supply.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM732

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