含蓄电池储能的分布式光伏发电控制策略研究

发布时间：2018-04-13 00:23

本文选题：分布式电源 + 光伏发电　；参考：《西南交通大学》2014年硕士论文

【摘要】：能源匮乏、环境污染以及电力需求增长给新能源分布式发电带来良好的发展契机。而在分布式发电系统中增加储能装置,能使其利用潜力更大,不仅能够为负载不间断供电,也可以更好的渗透于大电网中。合理有效的分布式电源控制技术是实现分布式电源与大电网并网发电的关键,成为近些年研究的热点。本文首先阐述光伏发电和蓄电池储能系统原理和特性。以并网逆变器作为分布式电源并网接口方式,研究两种控制策略：PQ控制和下垂控制,介绍其原理,并在Simulink中搭建模型进行仿真验证。其次,研究了前级电源光伏-蓄电池发电系统。针对光伏组网单元直流侧蓄电池双向DC/DC变换器研究了两种控制方法：功率外环电流内环和电压外环电流内环,并在模拟光照强度变化情况下进行仿真对比,结果表明功率外环电流内环能精准控制蓄电池输出功率,但不能直接控制直流母线电压,会随着能量波动而波动；而电压外环电流内环能直接对直流母线电压进行控制,利用直流母线电压高低来间接控制输出功率,更符合分布式光伏发电系统的实际应用,有效防止非计划性孤岛等情况,确保逆变器输出稳定。验证了通过蓄电池的充放电控制,能平抑光伏电池输出波动,保证逆变器前端直流母线电压很好地稳定在额定值。再次,设计了改进型的下垂控制。针对传统的V-Q下垂控制因未考虑线路压降情况导致无功分配有不准确、以及采用下垂控制造成的系统电压频率的误差,对下垂控制算法进行改进,通过引入线路压降和频率电压算法恢复有效地改善了无功分配不准和电压频率偏离额定值的情况。最后,将光-储系统接入微电网运行,搭建微电网仿真模型,研究其运行特性和控制策略。针对并网孤岛运行两种模式的平滑切换,研究了单模式和双模式控制策略,并各自进行仿真算例与对比。在PQ-Droop切换控制下,分析切换过程中波动振荡较大的原因,当DG提供的功率无法满足负荷所需,功率差额较大,无法平滑切换的情况,为保证对重要负荷的不间断供电,需切除次要负荷动作,研究了切负荷方法,比较一次切负荷和分开切负荷对于降低切换暂态振荡的效果。结果表明分开切负荷能有效降低暂态振荡,使得平稳过渡并稳定运行于孤岛运行模式。
[Abstract]:Lack of energy, environmental pollution and the growth of electricity demand bring a good opportunity for new energy distributed generation.Adding energy storage device to distributed generation system can make it use more potential, not only can supply the load uninterruptedly, but also can penetrate into the large power grid better.Reasonable and effective distributed power generation control technology is the key to realize the grid generation of distributed generation and large power grid, and has become a hot research topic in recent years.In this paper, the principle and characteristics of photovoltaic power generation and battery energy storage system are described.Using grid-connected inverter as the interface of distributed power supply, this paper studies two control strategies: PQ control and droop control, introduces its principle, and builds a model in Simulink for simulation.Secondly, the photovoltaic-battery power generation system is studied.In this paper, two control methods for DC side battery bidirectional DC/DC converter with photovoltaic cells are studied: the power outer loop current inner loop and the voltage outer current current inner loop, and the simulation results are compared under the condition of simulated illumination intensity change.The results show that the power outer loop current inner loop can accurately control the battery output power, but can not directly control the DC bus voltage, which will fluctuate with the energy fluctuation, and the voltage outer loop current inner loop can directly control the DC bus voltage.The use of DC bus voltage to indirectly control the output power is more in line with the practical application of distributed photovoltaic power generation system. It can effectively prevent unplanned isolated islands and ensure the output stability of the inverter.It is verified that the voltage fluctuation of photovoltaic cell can be suppressed by the charge and discharge control of battery and the voltage of DC bus at the front end of inverter can be stabilized at the rated value.Thirdly, the improved droop control is designed.In view of the inaccurate reactive power distribution caused by the traditional V-Q droop control without considering the voltage drop of the line, and the error of voltage frequency caused by the sagging control, the sagging control algorithm is improved.By introducing line voltage drop and frequency voltage algorithm, we can effectively improve the situation of inaccurate reactive power distribution and voltage frequency deviation from the rated value.Finally, the optical-storage system is connected to the micro-grid to run, and the simulation model of the micro-grid is built, and its operation characteristics and control strategy are studied.Aiming at the smooth switching between two modes of grid-connected islanding operation, the control strategies of single mode and double mode are studied, and the simulation examples are given and compared with each other.Under the PQ-Droop switching control, the reasons for the large fluctuation and oscillation in the switching process are analyzed. When the power provided by DG cannot meet the needs of the load, the power difference is large, and the switching can not be smooth. In order to ensure the uninterrupted power supply to the important load,The method of load shedding is studied to compare the effect of primary and separate load shedding on the reduction of switching transient oscillation.The results show that separation of load shedding can effectively reduce transient oscillation and make steady transition and stable operation in isolated island operation mode.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615;TM912

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