四桥臂PV-AF系统关键技术研究

发布时间：2018-01-28 19:48

  本文关键词： PV-AF系统 CPT MPPT 光伏发电系统 有源电力滤波器 重复H_∞控制 阻抗　出处：《中国矿业大学》2014年博士论文　论文类型：学位论文

【摘要】：近年来，在人类社会科技与经济高速发展的过程中，不可再生能源的大量使用带来了严重的环境污染和生态恶化的问题，严重地影响了社会的发展和人类的健康，太阳能、潮汐能和风能等可再生能源的利用引起了广泛的重视。光伏发电系统是太阳能利用的重要形式，而且具有有源滤波功能的光伏发电（PhotovoltaicPower Generation and Active Filter，PV-AF）系统拓宽了光伏发电系统的功能，在实现向电网注入有功电能的同时，还能有效地抑制电网中的谐波等问题，具有广阔的发展及应用前景。本文针对接入三相四线制低压电网的四桥臂PV-AF系统关键技术进行了研究。 在分析基于保守功率理论（Conservative Power Theory，，CPT）的谐波电流检测方法的基础上，针对电网电压畸变的情况，提出了一种基于电网电压消谐的改进型CPT谐波电流检测方法，通过提取公共连接点电压中的基波成分，抑制电压中谐波成分对补偿电流计算的影响。仿真和实验验证了所提方法的合理性及可行性。 最大功率点跟踪（Maximum Power Point Tracking，MPPT）技术是提高能量转换的关键环节，决定了四桥臂PV-AF系统的工作效率，本文对各种MPPT方法进行了比较，对扰动观察法在最大功率点（Maximum Power Point，MPP）附近的振荡进行了分析，研究了系统工作点处于MPP附近的判断方法，提出了一种扰动观察法与恒定电压法相结合的改进型MPPT新方法。实验和仿真表明该方法能够准确快速地跟踪最大功率点。 四桥臂PV-AF系统的控制策略中，电压外环用于直流侧电压的控制和最大功率点的跟踪，电流内环用于跟踪基波并网电流和电网中谐波电流指令，电流环控制性能至关重要，本文提出了一种基于PI和重复H_∞控制的复合控制器的电流环控制策略，PI控制环节保证系统的动态性能，内模环节使得稳态误差更小，鲁棒控制环节有效增强了系统的抗干扰性能，在连续域对复合控制器参数进行设计，通过离散化完成控制器的数字实现，并且在离散域中研究了离散化对系统性能的影响。在不同情况下对提出的复合控制器进行了实验和仿真验证，结果表明系统具有良好的动态性能、更小的稳态误差和优良的鲁棒性，具有穿越低电压区域的能力。 针对系统中存在的负阻抗将会影响系统稳定性的问题，本文研究了基于小信号模型的四桥臂PV-AF系统阻抗建模，对不同控制策略下参数变化对系统阻抗特性的影响进行了比较研究。验证了优化后的复合控制器参数，在保证系统性能的前提下，能够有效地减小负阻抗对系统稳定性的影响。 主电路参数是影响四桥臂PV-AF系统性能的关键因素之一，本文对四桥臂PV-AF系统主电路参数进行了设计，对器件进行了选型，搭建了5kVA三相四桥臂PV-AF系统实验平台。
[Abstract]:In recent years, in the process of rapid development of science, technology and economy of human society, the massive use of non-renewable energy has brought serious environmental pollution and ecological deterioration problems. Has seriously affected the development of society and human health, solar energy, tidal energy and wind energy and other renewable energy utilization has attracted widespread attention. Photovoltaic power generation system is an important form of solar energy utilization. And the photovoltaic power Generation and Active Filter with active filter function. PV-AFS system broadens the function of photovoltaic power generation system and can effectively suppress the harmonics while injecting active power into the power grid. In this paper, the key technologies of four-arm PV-AF system connected to three-phase four-wire low-voltage power network are studied. Based on the analysis of harmonic current detection method based on conservative power theory, Conservative Power Theoryne (CPT), this paper aims at the situation of voltage distortion in power grid. An improved CPT harmonic current detection method based on grid voltage harmonic elimination is proposed. The fundamental component of common connection voltage is extracted. The influence of harmonic components in the suppression voltage on the calculation of the compensation current is verified by simulation and experiments, and the rationality and feasibility of the proposed method are verified. Maximum Power Point tracking (MPPT) is a key step to improve energy conversion. The efficiency of the four-arm PV-AF system is determined. In this paper, various MPPT methods are compared, and the perturbation observation method is compared at maximum Power Point. The oscillation near MPP) is analyzed, and the judgment method of system working point near MPP is studied. An improved MPPT method combining perturbation observation method with constant voltage method is proposed. Experiments and simulations show that the proposed method can track the maximum power points accurately and quickly. In the control strategy of four-arm PV-AF system, the voltage outer loop is used to control the DC side voltage and track the maximum power point, and the current inner loop is used to track the fundamental grid-connected current and the harmonic current instructions in the power network. The performance of current loop control is very important. In this paper, a current loop control strategy based on Pi and repetitive H _ 鈭

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