光伏并网系统低电压穿越控制方法的研究

发布时间：2018-01-10 10:21

本文关键词：光伏并网系统低电压穿越控制方法的研究　出处：《东北电力大学》2017年硕士论文　论文类型：学位论文

【摘要】：近些年随着化石能源的大量消耗,环境污染问题日益严重,为了解决资源枯竭和环境污染问题需要大量开发和利用可再生能源。在诸多类型的新能源中光伏发电具有利用成本低、效率高、无污染等优点,是目前最重要的新能源之一。但是对太阳能的开发利用的研究目前还存在很多问题,这些问题制约着光伏并网发电的大规模应用。低电压穿越技术不仅要求在系统正常运行时保证光伏系统输出的电能质量,同时在系统出现一定程度的故障时保持光伏组件持续向电网输出,同时充分利用光伏逆变器的快速无功输出能力,在故障穿越期间为系统提供一定的无功,协助电网电压恢复正常。本文是从光伏系统的网端角度进行了故障穿越控制策略的研究,目前光伏系统在故障穿越过程中在进行正负序分离控制时会有一定的误差,针对这一问题本文研究了一种降阶的谐振调节器(ReducedResonanceOrder,ROR),该控制器的功能就是将控制过程中的二阶谐振环节降阶为两个不同极性的一阶滤波器环节,一阶复数滤波器可以克服二阶谐振环节对正负序分量无选择的缺点。为了使控制器在光伏并网系统软件和硬件固有误差范围内发挥更好的效果,本文引入了截止频率来增大ROR控制器的频带宽度。并应用博德图(Bode)来分析所研究的控制器中截止频率效果及系统的最优性能。搭建光伏并网系统的仿真模型,以此来验证本文应用的ROR调节器可提高光伏系统在故障穿越过程中基波的正负序分离的速度。在分析传统PLL-SRF(同步参考坐标系锁相环)工作原理和小信号模型的基础上,根据系统稳态及动态响应设计了合适的锁相环参数;针对电网电压不平衡且谐波畸变下PLL-SRF检测的基波正序分量中含有负序和谐波分量而致使其不能工作的问题,提出了基于不平衡谐波补偿机制(Mechanismon Compensati Harmonic Unbalanced,UHCM)模块的三相锁相环,并扩展研究了通过滤波结构并联的方式消除低次谐波对锁相环的影响。在光伏并网系统数学模型建立的基础上,对并网故障穿越特别是不对称故障下的并网控制原理给出了合理的数学分析,并计算得出了传统故障穿越电流控制目标。通过仿真验证发现传统的控制策略存在算法复杂、控制目标对平衡短路电流和短路功率的能力有限以及直流侧母线电压控制不合理等缺点。针对传统故障穿越控制策略的缺陷本文提出了最大电流幅值控制策略,并结合所研究的正负序分量分离技术,通过仿真验证所提控制方法可以在电压跌落期间能够稳定光伏系统交流以及直流侧的电压水平,在故障期间为电网提供一定量的无功支撑,帮助系统电压逐步恢复正常。
[Abstract]:In recent years, with the consumption of fossil energy, the problem of environmental pollution is becoming more and more serious. In order to solve the problem of resource depletion and environmental pollution, a large number of renewable energy sources need to be developed and utilized. Photovoltaic power generation has the advantages of low cost, high efficiency and no pollution in many kinds of new energy sources. It is one of the most important new energy sources, but there are still many problems in the research of solar energy development and utilization. These problems restrict the large-scale application of grid-connected photovoltaic power generation. Low-voltage traversing technology not only requires to ensure the power quality of photovoltaic system output in the normal operation of the system. At the same time, keep the photovoltaic module out to the power grid continuously when there is a certain degree of fault, and make full use of the fast reactive power output ability of the photovoltaic inverter, and provide a certain reactive power for the system during the period of fault passing. In this paper, the fault crossing control strategy is studied from the point of view of the grid end of the photovoltaic system. At present, there will be some errors in the control of positive and negative sequence separation in the fault passing process of photovoltaic system. In this paper, we study a reduced order resonant regulator called reduced Resonance order order (ROR). The function of the controller is to reduce the order of the second order resonance in the control process to the first order filter with two different polarities. The first-order complex filter can overcome the disadvantage that the second-order resonant link has no choice for the positive and negative sequence components. In order to make the controller play a better effect in the inherent error range of the software and hardware of the photovoltaic grid-connected system. In this paper, cutoff frequency is introduced to increase the bandwidth of ROR controller. To analyze the cutoff frequency effect of the controller and the optimal performance of the system. Build the photovoltaic grid-connected system simulation model. It is verified that the ROR regulator in this paper can improve the speed of the positive and negative sequence separation of the fundamental wave in the process of fault passing through the photovoltaic system. In the analysis of the traditional PLL-SRF (synchronous reference coordinate system phase-locked loop). Working principle and small signal model based on. Appropriate PLL parameters are designed according to the steady and dynamic responses of the system. In order to solve the problem that the fundamental sequence component of PLL-SRF detected under unbalanced voltage and harmonic distortion has negative sequence and harmonic component, it can not work. Based on unbalanced harmonic compensation mechanism, mechanismon Compensati Harmonic Unbalanced is proposed. The three-phase phase-locked loop of UHCM module is studied. The influence of low-order harmonics on phase-locked loop is eliminated by parallel filter structure. The mathematical model of photovoltaic grid-connected system is established. Reasonable mathematical analysis of grid-connected control principle for grid-connected fault traversing, especially under asymmetric fault is given. The traditional fault traversing current control target is calculated and the simulation results show that the traditional control strategy has complex algorithm. The control target has limited ability to balance short circuit current and short circuit power, and the DC bus voltage control is unreasonable. Aiming at the defects of traditional fault crossing control strategy, a maximum current amplitude control strategy is proposed in this paper. Combined with the research on the separation of positive and negative sequence components, the simulation results show that the proposed control method can stabilize the voltage level of AC and DC side of PV system during voltage sag. It provides a certain amount of reactive power support to the power network during the fault period, and helps the system voltage to return to normal step by step.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615

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