含风电微电网孤岛运行控制与优化

发布时间：2019-05-06 10:15

【摘要】：在环境污染、能源危机等多方面的压力下,包含风能、太阳能等可再生能源的分布式发电成为电气领域的一个研究热点。分布式电源(DG)、储能装置以及负荷按照一定的拓扑结构可组成微电网,因此微电网的发展是实现分布式电源大规模应用的关键。微电网有并网运行和孤岛运行两种模式,能够为大电网提供补充,提高区域供电可靠性和电能质量。本文以包含风力发电的微电网为研究对象,对其孤岛运行采用下垂控制策略出现的问题进行了详细研究。针对微电网中线路阻抗不匹配造成的无功功率不合理分配,提出了一种基于PARK变换的线路阻抗辨识新方法,对线路阻抗值进行了在线辨识,并用得到的线路阻抗值对无功功率下垂系数进行了修正。通过仿真和搭建的实验平台,验证了所提出方法的有效性和可行性。同时,为了分析下垂系数变化时系统的稳定性,建立了微电网小信号模型,并通过求解系统状态矩阵的特征值,判断系统稳定性。其次,针对上述提到无功功率不合理分配问题,本文提出了一种基于线路压降补偿的改进下垂控制。这种控制策略在传统下垂控制基础上加入线路压降补偿,通过平移下垂特性曲线,保证各分布式电源输出电压一致,实现无功功率的精确分配。此外,由于下垂控制存在稳态误差,因此在一次控制的基础上加入了二次控制,使得微电网电压、频率能够恢复至允许的范围内。再次,针对微电网中风电-储能系统的协调控制,本文设计了一种基于直流母线电压自适应调节的改进下垂控制。在风能或负载变化时,通过动态平移下垂特性曲线,实现最大程度地利用风电,波动引起的功率差额则由储能系统进行补偿。最后,针对三相负荷不对称造成的微电网交流母线电压三相不平衡,本文在控制策略中增加了负序电压抑制。利用Matlab/Simulink仿真对比了采用电压电流双闭环控制和所设计的正负序电压电流控制两种方法,证明了所设计的方法可有效地降低交流母线的不平衡度。
[Abstract]:Under the pressure of environmental pollution and energy crisis, distributed power generation, which includes renewable energy such as wind and solar energy, has become a research hotspot in electrical field. The (DG), energy storage device and load of distributed power supply can form microgrid according to a certain topology, so the development of microgrid is the key to realize the large-scale application of distributed power supply. There are two modes of micro-grid operation: grid-connected operation and island operation, which can supplement the large power grid and improve the reliability and power quality of regional power supply. In this paper, the problems of sag control strategy used in island operation of micro-grid including wind power generation are studied in detail. In view of the unreasonable allocation of reactive power caused by the mismatch of line impedance in microgrid, a new method of line impedance identification based on PARK transform is proposed, and on-line identification of line impedance is carried out. The sag coefficient of reactive power is modified by using the line impedance value obtained. The validity and feasibility of the proposed method are verified by simulation and experimental platform. At the same time, in order to analyze the stability of the system when the droop coefficient changes, the small signal model of the microgrid is established, and the stability of the system is judged by solving the eigenvalues of the state matrix of the system. Secondly, an improved droop control based on line voltage drop compensation is proposed to solve the problem of unreasonable distribution of reactive power. This control strategy adds line voltage drop compensation on the basis of traditional droop control. By translating droop characteristic curve, the output voltage of each distributed power supply can be guaranteed to be consistent and the reactive power distribution can be realized accurately. In addition, due to the steady-state error of droop control, the secondary control is added on the basis of primary control, so that the voltage and frequency of microgrid can be restored to the allowable range. Thirdly, for the coordinated control of wind power and energy storage system in microgrid, an improved droop control based on DC bus voltage adaptive regulation is designed in this paper. When the wind energy or load changes, the maximum utilization of wind power can be achieved by means of the dynamic translation droop curve, and the power difference caused by the fluctuation is compensated by the energy storage system. Finally, in view of the three-phase unbalanced AC bus voltage caused by three-phase load asymmetry, negative sequence voltage suppression is added to the control strategy in this paper. Two methods of voltage-current double closed-loop control and positive-negative sequence voltage-current control are compared by Matlab/Simulink simulation. It is proved that the designed method can effectively reduce the unbalance degree of AC bus.
【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】：TM727

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