一种直流微电网的分层能量管理控制策略研究

发布时间：2018-07-10 06:32

本文选题：直流微电网 + 直流母线电压　；参考：《西南交通大学》2014年硕士论文

【摘要】：面对环境污染和能源短缺的双重压力,清洁经济的分布式发电技术得到了广泛的应用。但大规模分布式电源的并网运行会对大电网的安全可靠运行造成不可忽略的影响。为了防止这一弊端,微电网的概念应运而生。微电网既能高效的利用新能源,又能参与电力市场管理,具有灵活性强,交互性好的特点。根据微电网中母线电流的性质,可以将微电网划分为直流微电网、交流微电网以及交直流混合微电网三种类型。与后两者相比,直流微电网具有效率高、损耗低、可控性强等优点,但直流微电网由于容量有限,抗扰动能力弱,在运行条件发生变化时,容易引起直流母线电压的波动和电能质量的降低。因此需要设计合适的能量管理控制策略维持母线电压稳定,管理微电网电能质量。论文从分布式电源的建模出发,建立了直流微电网的控制模型,对直流微电网的分层能量管理控制策略进行了研究。首先,阐述了光伏电源的工作原理,建立了光伏电源的工程实用模型,在此基础上,采用爬山法对光伏电源的输出进行了最大功率跟踪,仿真结果表明,即使光照强度和环境温度发生变化,光伏电源也能实现最大功率的输出,验证了最大功率跟踪算法的有效性；分析了蓄电池的充放电动作原理,建立了完整的蓄电池充放电模型,仿真结果表明,该模型可以根据蓄电池的SOC状态切换充放电动作,能够良好的反映蓄电池的物理特性；介绍了双向AC/DC变换器的工作原理,设计了解耦控制模型,从仿真结果可以看出,通过控制变换器在整流和逆变两种工作状态之间的切换,可以实现能量的双向流动。其次,根据直流微电网在不同运行模式下的工作特性,以母线电压的大小为依据,对光伏电源、蓄电池、双向AC/DC变换器、负载分别设计了控制策略。其中,控制光伏电源工作在最大功率追踪输出和恒压模式两种运行状态；设计了蓄电池的下垂控制策略,根据母线电压的大小调节蓄电池的充放电功率；通过切换双向AC/DC变换器的工作状态,实现能量在微电网和大电网之间的双向流动；在系统重载的情况下采用切负载策略使母线电压恢复到正常范围。仿真结果表明,联网状态下,通过AC/DC变换器平衡功率差额,能够保证母线电压维持在额定值；孤岛状态下,下垂控制可以使母线电压维持在合理范围,但会产生电压偏差。然后,分析了下垂控制导致母线电压偏差的原因,在此基础上,给出了母线电压恢复控制策略,其实质是控制蓄电池充放电功率,以准确匹配光伏电源输出功率与负载需求之间的功率差额。仿真结果表明,采用电压恢复控制策略,即使光照强度和负载大小发生变化,母线电压也能维持在额定值：但当光伏电源和负载之间的功率差额超过蓄电池功率上限时,母线电压恢复控制策略失效,母线电压仍会产生偏差。最后,在下垂控制和母线电压恢复控制的基础上,研究了直流微电网的组网运行控制策略,从而形成了直流微电网的分层控制结构。考虑蓄电池功率限制的四种工况仿真结果表明,通过改变网间电流的大小和方向,可以实现能量在微电网之间的双向流动,但同时会导致母线电压的偏差,电压偏差的大小只与网间电流大小有关,当蓄电池容量受限时,网间电流可能发生跳变,引起电压偏差的改变。
[Abstract]:In the face of the double pressure of environmental pollution and energy shortage, the distributed generation technology of clean economy has been widely used. However, the grid operation of large-scale distributed power supply can not be neglected in the safe and reliable operation of large power grid. In order to prevent this disadvantage, the concept of microgrid emerges as the times require. With the new energy and the power market management, it has the characteristics of strong flexibility and good interactivity. According to the nature of the bus current in the microgrid, the micro grid can be divided into three types of DC micro grid, AC microgrid and AC and DC hybrid microgrid. Compared with the latter two, the DC micro grid has high efficiency, low loss and strong controllability. But the DC micro grid is weak because of its limited capacity and weak anti disturbance ability. When the operating conditions change, it will easily cause the fluctuation of DC bus voltage and the reduction of power quality. Therefore, a suitable energy management and control strategy should be designed to maintain the voltage stability of the bus and manage the power quality of the microgrid. The paper is based on the modeling of the distributed power supply. The control model of DC microgrid is established, and the hierarchical energy management control strategy of DC microgrid is studied.
First, the working principle of photovoltaic power supply is expounded, and the practical model of the photovoltaic power supply is set up. On this basis, the maximum power tracking of the output of the photovoltaic power is carried out by the mountain climbing method. The simulation results show that the maximum power output can be realized even if the light intensity and the ambient temperature change, and the maximum power is verified. The efficiency of the rate tracking algorithm is presented. The charge discharge action principle of the battery is analyzed and a complete battery charging and discharging model is set up. The simulation results show that the model can switch charge and discharge according to the SOC state of the battery, and can reflect the physical characteristics of the battery well. The working principle of the bidirectional AC/DC converter is introduced and the design is introduced. In order to understand the coupling control model, it can be seen from the simulation results that the bidirectional flow of energy can be realized by controlling the switching between the two working states of the rectifier and the inverter.
Secondly, according to the working characteristics of the DC microgrid in different operating modes, based on the size of the bus voltage, the control strategy is designed for the photovoltaic power, the battery, the bidirectional AC/DC converter, and the load of the photovoltaic power is controlled in two operating states of the maximum power tracking output and the constant voltage mode; and the battery is designed. The droop control strategy adjusts the charge and discharge power of the battery according to the voltage of the bus. By switching the working state of the bidirectional AC/DC converter, the energy is achieved in the two-way flow between the microgrid and the large power grid. Under the heavy load of the system, the load strategy is used to restore the voltage of the bus to the normal range. The simulation results show that the combined power of the bus is restored to the normal range. In the network state, the balance of the power difference between the AC/DC converter can ensure that the bus voltage is maintained at the rated value. Under the island state, the droop control can keep the bus voltage in a reasonable range, but the voltage deviation will be produced.
Then, the cause of the bus voltage deviation caused by droop control is analyzed. On this basis, the control strategy of the bus voltage recovery is given. The essence is to control the charge and discharge power of the battery to accurately match the power difference between the output power of the photovoltaic power supply and the load demand. The simulation results show that the voltage recovery control strategy is adopted, even if the light is illuminated. The strength and load size change, the bus voltage can also be maintained at the rated value: but when the power difference between the photovoltaic power and the load is higher than the upper limit of the battery power, the bus voltage recovery control strategy is invalid and the bus voltage will still have a deviation.
Finally, on the basis of droop control and bus voltage recovery control, the control strategy of network operation of DC micro grid is studied, and the hierarchical control structure of DC microgrid is formed. The simulation results of four operating conditions considering the power limit of the battery show that the energy can be realized by changing the size and direction of the current between the network. The two-way flow between the networks, but at the same time leads to the bias of the bus voltage. The size of the voltage deviation is only related to the size of the Internet current. When the capacity of the battery is limited, the current between the networks may jump and cause the change of the voltage deviation.
【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】：TM727

【参考文献】