基于LCL滤波器的光伏发电并网系统的研究

基于 LCL 滤波器的光伏发电并网系统的研究 II Abstract The two major problems of energy crisis and environmental pollution restrict the economic development of all countries in the world, and clean renewableenergy hasbecome a hot spot of researchin all countries.With its unique advantages,solar energy has beenfirst to the development in the field of new energy ratio increasedyear by year,andit is urgent to develop the grid connected technology of photovoltaic power generation.Therefore, the photovoltaic power generation grid connectedsystem is taken as the researchobject in this paper,focusing on the maximum power point tracking algorithm for photovoltaic cells, LCL filter parameters and inverter grid control strategy.The specific content and results are as follows: 1. The working principle of photovoltaic cell is studied, and the equivalent mathematical model is established.The output characteristic curve under different conditions is simulated, and the principle and method of maximum power point tracking (MPPT) of photovoltaic cell is analyzed.The pv array output power voltage (P-U) characteristic curve under partial shading becomesmore peak situation.In this condition,the traditional tracking method of maximum power point is failure.To overcome this difficulty,a composite MPPT method is proposed, which is mainly divided into two parts. Firstly, particle swarm optimization algorithm is applied to solve several pole problems, and it can locate near the maximum power point quickly and use the secondary search based on the incremental conductancemethod and accurately find the global optimal solution.Finally, the simulation experimentsare carried out in the Boost circuit. The results show that no matter the pv arrays is partially shadedor not,the result of the compound control method is more accuratethan the particle swarm optimization algorithm and incremental conductance and proves that the algorithm is correct and effective. 2. The topology and output filter structure of three-phasegrid connected inverter are introduced.Comparedwith the sameinductancevalue of LCL filter and L filter, the former is more ideal for high-frequency harmonic suppression,and it is widely used in the grid connectedsystem.However,thereis a resonantspike in the LCL filter,and the parametersof the components interact with each other. It is also difficult to design and get the results quickly and accurately.Based on it,a mathematical model of LCL grid connected inverter system is established,and two ways to suppressthe resonantpeak are analyzed. Meanwhile, the parameter design of LCL filter is mainly studied.Considering the constraints of each parameter, the particle swarm optimization (PSO) algorithm is proposed to optimize the parameters of the LCL filter, and the algorithm flow is introduced in detail. Finally, the 西华大学硕士学位论文 III parametergroups of the LCL filter are quickly obtained by simulation. The fitness values are all in line with the conditions, and the parameter group with the minimum fitness value is selectedfor simulation verification in the grid-connectedinverter system. 3. Aiming at the LCL-type inverter grid-connected system, the closed-loop control of the network side current and the closed-loop control of the inverter side current are compared and analyzed.According to the obtained root locus map, the latter closed-loop control system is more stable.At the same time, to improve the power factor of the system, the capacitive current loop is introduced and the double loop control is establishedon the basisof the single current loop. After the simulation experiment, the parameter values of the particle swarm optimization and the traditional design method are compared respectively. The filter parameters designed by the particle swarm optimization algorithm have better filtering performance, and the harmonic distortion rate is obviously reduced by FFT analysis, which proves the correctnessand superiority of the method.Finally,a three-phasephotovoltaic power generation grid-connected system model is built,and the voltage outer loop is added to the current double loop. The simulation results verify the effectiveness of the three-loop control strategyand the stability of the system. Key Words ： Maximum power point tracking; LCL filter;Grid-connected inverter; shading;Particleswarm optimization algorithm 基于 LCL 滤波器的光伏发电并网系统的研究 IV 目 录 摘 要 .I AbstractII 1 绪论 .1 1.1 课题研究背景及意义 1 1.2 国内外研究现状 2 1.2.1 并网逆变器拓扑结构 .4 1.2.2 最大功率点跟踪算法 .5 1.2.3 交流输出滤波技术 .5 1.2.4 并网逆变器控制方法 .6 1.3 本文研究主要内容 6 2 光伏发电原理及输出特性分析 .8 2.1 光伏发电原理 8 2.2 光伏电池数学模型 9 2.3 光伏电池输出特性 11 2.4 遮蔽条件下光伏阵列输出特性 13 2.5 本章小结 15 3 光伏系统最大功率点跟踪方法研究 .16 3.1 最大功率点跟踪原理 16 3.2 传统的最大功率点跟踪方法 17 3.2.1 恒定电压法 .17 3.2.2 扰动观测法 .17 3.2.3 电导增量法 .18 3.3 遮蔽条件下的最大功率点跟踪方法 20 3.4 基于粒子群算法的全局 MPPT 算法研究 .21 3.4.1 粒子群算法 .21 3.4.2 粒子群算法和电导增量法的复合 MPPT 控制 22 3.5 仿真分析 24 3.6 本章小结 27 4 LCL 型并网逆变器的建模与分析 28 4.1 三相并网逆变器的拓扑结构 28 西华大学硕士学位论文 V 4.2 三相并网逆变器输出滤波器结构 29 4.3 LCL 型并网逆变器数学模型 .31 4.3.1 三相静止坐标系下的数学模型 .31 4.3.2 两相旋转坐标系下的数学模型 .34 4.4 本章小结 37 5 LCL 滤波器参数的分析与设计 39 5.1 LCL 滤波器的谐振抑制及仿真分析 .39 5.2 LCL 滤波器参数约束 .41 5.2.1 谐振频率约束条件 .41 5.2.2 总电感约束条件 .41 5.2.3 滤波电容约束条件 .41 5.3 LCL 滤波器参数粒子群优化算法 .42 5.3.1 粒子的确定 .42 5.3.2 适应度函数的建立 .42 5.3.3 约束条件 .42 5.3.4 优化流程 .42 5.3.5 仿真结果 .43 5.4 本章小结 44 6 LCL 型并网逆变器控制策略 45 6.1 控制策略分析 45 6.1.1 网侧电流闭环控制策略分析 .45 6.1.2 逆变器侧电流闭环控制策略分析 .47 6.2 基于逆变器侧电流和电容电流双环控制策略 48 6.3 仿真分析 50 6.3.1 逆变器并网控制框图 .50 6.3.2 LCL 滤波器仿真效果比较 51 6.3.3 光伏发电系统并网运行仿真分析 .55 6.4 本章小结 59 7 总结与展望 .61 参 考 文 献 .63 攻读硕士学位期间发表的论文及科研成果 .67 致 谢 .68 西华大学硕士学位论文 1 1 绪论1.1 课题研究背景及意义 世界各地的能源需求量逐年增加，而化石燃料正在枯竭，人类正面临能源危机和环 境污染两大难题。煤炭、石油和天然气等仍是支撑各国继续发展的主要能源，据世界卫 生组织估计，再过四十年，若人均能源消费达到今天发达国家平均水平，那么将有三分 之一的主要矿物质资源消耗殆尽 [1] 。同时，化石燃料的过度开采会破坏生态平衡，导致 水污染和土地沙漠化的现象，燃烧后产生的温室气体会造成全球气候变暖，长期以往， 冰山融化，海平面上升，增加了自然灾害发生几率。最近几年来，一到秋冬季节，空气 中的 PM2.5含量大大的提高， 各地雾霾天气越来越严重， 已经妨碍了我们正常生活和损 害身体健康。全球各国都在积极支持节能减排的政策，改变能源结构大势所趋， 2015 年的巴黎气候峰会上， 全球第一次成功达成减排协议， 表明各国为低碳转型的决心。 《巴 黎协定》表明，各国广泛研究可再生能源，希望到 2050 年后，新能源能彻底替代化石 能源。作为能源开采和消耗大国，表 1.1 为我国主要化石燃料的储采对比量，从表中可 以看出我国化石能源已处于严重短缺状态，为解决上述矛盾，使得开发清洁有效的可再 生能源的重要性达到前所未有的高度。 表 1.1 主要化石能源统计表 Table 1.1 Major fossil energy statistics 化石能源 探明储量 占世界比 产量 占世界比 储采比（年） 煤炭 （百万吨） 114500 12.8% 3874 46.9% 30 石油 （百万吨） 2500 1.1% 211.4 5% 11.9 天然气（十亿 立方米） 3500 1.8% 134.5 3.9% 25.7 地球上有很多资源可供我们开采，满足可再生和无污染两个要求的能源也有很多， 太阳能以其分布广泛，无污染，不产生有害气体，随时可用不受地理位置影响等优点而 被广泛研究，具有很好的发展前景。据世界能源结构的预测，按照现在的发展趋势，到