光伏发电并网控制策略研究

发布时间：2018-07-10 06:54

本文选题：光伏系统 + 准Z源　；参考：《长春工业大学》2017年硕士论文

【摘要】：随着光伏发电技术的快速发展,光伏发电并网系统得到越来越广泛地应用。但是光伏发电并网系统复杂多变的外部条件,对保证光伏阵列输出稳定和安全可靠并入电网的控制策略提出了更高的要求,而MPPT控制策略和逆变控制策略是并网控制策略中的核心部分,影响着并网系统的发电效率和并网电流的质量,所以有必要对并网控制策略进行研究。本文以大功率三相光伏发电并网系统作为研究对象,以光伏并网逆变器稳定、高效、低谐波运行为目标,展开了理论研究和仿真验证。介绍了光伏发电并网系统的四个核心部分:光伏阵列输入、前级DC/DC变换器和MPPT控制算法、后级DC/AC逆变器控制策略、滤波器参数设计。论文针对这四个主要部分开展的研究内容如下:首先分析了光伏电池的内部特性,建立数学模型和仿真模型,得到单个电池的输出特性曲线;又分析了光伏阵列在出现多极点时的数学模型,通过MATLAB仿真平台搭建仿真模型,得到了光伏阵列在出现多极点时的输出波形。其次针对光伏阵列在外部条件变化时输出电压不稳的问题提出了在交错调制策略下使系统前级变换器具有电压增益范围宽,输出直流电压稳定的新型准Z源三电平Boost直流变换器,为后级逆变环节提供稳定的输入奠定基础;针对常用MPPT算法不能满足多极点情况下最大功率点追踪的问题,引入了适用于多极点寻优的粒子群优化算法并通过改进,实现在出现多极点时可以准确追踪到最大功率点。然后采用SVPWM控制策略作为后级逆变器调制方法,通过导通信号控制开关器件的导通与关断实现能量的转换;在研究PI并网控制策略的基础上,引入设计与控制更为简单的PR控制策略,并改进为准PR控制策略,通过参数设计和仿真验证,证明了在该控制策略下三相光伏并网系统具有较高的并网电流质量和较强的抗电网干扰能力。对比分析L型、LC型和LCL型滤波器优缺点,选取LCL型滤波器进行滤波,并给出滤波器参数的设计方法。最后根据建立的三相光伏发电并网系统的MATLAB仿真模型,对论文提出的控制策略与参数设计进行仿真验证,仿真结果证明了所选控制策略的正确性和有效性,表明了系统输出并网电流符合有功功率和无功功率的控制标准,达到了并网电流总谐波指标要求,满足了并网电流跟踪响应速度。
[Abstract]:With the rapid development of photovoltaic technology, photovoltaic grid-connected system has been more and more widely used. However, because of the complex and changeable external conditions of photovoltaic grid connection system, the control strategy to ensure the stability of photovoltaic array output and the safe and reliable integration of photovoltaic array into the grid has put forward higher requirements. MPPT control strategy and inverter control strategy are the core of grid-connected control strategy, which affect the generation efficiency and the quality of grid-connected current, so it is necessary to study the grid-connected control strategy. In this paper, the high-power three-phase photovoltaic grid-connected system is taken as the research object, the photovoltaic grid-connected inverter is stable, efficient and low harmonic operation as the goal, the theoretical research and simulation are carried out. Four core parts of grid-connected photovoltaic system are introduced: photovoltaic array input, DC / DC converter and MPPT control algorithm, DC / AC inverter control strategy and filter parameter design. The main contents of this paper are as follows: firstly, the internal characteristics of photovoltaic cell are analyzed, and the mathematical model and simulation model are established to get the output characteristic curve of a single cell. The mathematical model of photovoltaic array with multiple poles is analyzed, and the output waveform of photovoltaic array is obtained by MATLAB simulation platform. Secondly, aiming at the problem that the output voltage of photovoltaic array is unstable when the external conditions change, it is proposed that the voltage gain range of the system's front converter is wide under the staggered modulation strategy. A new type of quasi-Z source three-level boost converter with stable output DC voltage lays the foundation for providing stable input for the back stage inverter, aiming at the problem that common MPPT algorithm can not satisfy the problem of maximum power point tracing in multi-pole case. A particle swarm optimization algorithm suitable for multi-pole optimization is introduced and improved to accurately track the maximum power point in the presence of multiple poles. Then the SVPWM control strategy is used as the modulation method of the back inverter, and the switching on and off of the switch device is realized by the on-signal control. On the basis of studying the Pi grid-connected control strategy, The PR control strategy, which is simpler in design and control, is introduced, and the quasi-PR control strategy is improved, which is verified by parameter design and simulation. It is proved that the three-phase photovoltaic grid-connected system has high grid-connected current quality and strong anti-interference ability under the control strategy. The advantages and disadvantages of L type LC filter and LCL type filter are compared and analyzed. LCL filter is selected to filter and the design method of filter parameters is given. Finally, according to the MATLAB simulation model of the three-phase photovoltaic grid-connected system, the control strategy and parameter design proposed in this paper are simulated and verified. The simulation results prove the correctness and effectiveness of the proposed control strategy. It is shown that the system output grid-connected current accords with the control standard of active power and reactive power, meets the requirements of total harmonics of grid-connected current, and meets the speed of tracking response of grid-connected current.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615

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