光伏并网逆变器及MPPT算法研究

发布时间：2018-04-30 06:57

本文选题：并网逆变器控制 + 重复控制　；参考：《中国矿业大学》2017年硕士论文

【摘要】：随着环境污染日益加重以及全球对能源的需求日益增长,化石能源将会被慢慢舍弃,取而代之的是以太阳能为首的清洁新能源。为了提高光伏并网逆变器控制性能,提高发电效率,光伏并网逆变器控制技术及新型的最大功率点跟踪(MPPT)技术是如今的研究热点。本文选取三相带Boost升压两电平逆变器系统作为研究对象,对其前级MPPT控制算法、并网逆变器控制策略等展开研究。首先,对三相并网逆变器进行数学建模,设计了双闭环控制器参数,针对直流母线电压和电网电压的扰动以及并网电流对电网的冲击问题,在电流内环加入了电压前馈,改善了并网逆变器的动态性能;针对只使用PI调节器时并网电流总畸变率(THD)偏高的问题,研究了采用PI控制与重复控制相结合的并网策略,对于电网的扰动和含有的谐波有较好的抑制作用,系统的稳态精度提高,抗干扰能力增强;针对电网电压不平衡,采用基于对称分量法的三相软件锁相环,提高了系统抗干扰的能力。通过对双闭环并网逆变器的仿真分析,证明该控制策略在电网电压突变、频率变化以及含谐波情况下具有良好的动态性和稳定性。其次,对光伏阵列进行工程建模与输出特性分析,基于MPPT的基本原理,设计了光伏电池MPPT装置,研究并改进了几种传统的MPPT控制算法,并通过仿真分析比较各自的优势与不足,最后采用了一种带滞环比较的变步长扰动观测法,此方法可以消除稳定过程中的功率波动,解决了寻优过程的误判问题,仿真结果证明了该控制方法的有效性。再次,对于局部阴影条件下的光伏阵列进行建模,针对传统方法对于多峰值情况下跟踪失效的问题,研究分析了对于两个峰值情况下的重新选择参考电压的电导增量法,针对三个及以上峰值的情况,本文基于烟花爆炸寻优算法的原理,提出新型的MPPT算法,可以避免陷入局部最大功率点,具有跟踪快速且准确的优点,随后通过仿真验证了该方法的可行性,满足跟踪要求。最后,搭建了1.8k W并网实验平台,进行了参数设计、选型、硬件电路设计,通过DSP软件编程,对光伏并网策略以及MPPT算法进行了实验研究,分析了实验结果,验证了可行性与有效性。
[Abstract]:As environmental pollution intensifies and global demand for energy grows, fossil fuels will be scrapped and replaced by clean new sources of energy, led by solar energy. In order to improve the control performance of grid-connected photovoltaic inverter and improve the efficiency of generation, the control technology of grid-connected photovoltaic inverter and the new maximum power point tracking (MPPTT) technology have become a hot research topic. In this paper, the three-phase Boost boost two-level inverter system is chosen as the research object, and its MPPT control algorithm and grid-connected inverter control strategy are studied. Firstly, the mathematical model of the three-phase grid-connected inverter is established, and the parameters of the dual-closed-loop controller are designed. In view of the disturbance of DC bus voltage and grid voltage and the impact of grid-connected current on the grid, the voltage feedforward is added to the current inner loop. The dynamic performance of grid-connected inverter is improved, and the strategy of combining Pi control with repetitive control is studied to solve the problem of high total distortion rate (THD) of grid-connected current when Pi regulator is used only. It can restrain the disturbance and harmonics of the power network, improve the steady-state precision of the system and enhance the anti-interference ability. In view of the voltage imbalance of the power system, a three-phase software phase-locked loop based on symmetric component method is adopted. The anti-interference ability of the system is improved. Through the simulation analysis of double closed loop grid-connected inverter, it is proved that the control strategy has good dynamic and stability in the case of voltage abrupt change, frequency change and harmonic. Secondly, the engineering modeling and output characteristic analysis of photovoltaic array are carried out. Based on the basic principle of MPPT, the photovoltaic cell MPPT device is designed, several traditional MPPT control algorithms are studied and improved, and their advantages and disadvantages are compared by simulation analysis. Finally, a variable step size perturbation observation method with hysteresis comparison is used. This method can eliminate the power fluctuation in the stable process and solve the problem of misjudgment in the optimization process. The simulation results show the effectiveness of the control method. Thirdly, the photovoltaic array under the condition of local shadow is modeled. Aiming at the problem of tracking failure in the case of multi-peak value by traditional method, the conductance increment method for re-selecting reference voltage under two peak values is studied and analyzed. For three or more peak values, based on the principle of fireworks explosion optimization algorithm, a new MPPT algorithm is proposed, which can avoid falling into local maximum power points, and has the advantages of fast and accurate tracking. The feasibility of the method is verified by simulation, and the tracking requirement is satisfied. Finally, a 1.8kW grid-connected experimental platform is built, including parameter design, type selection, hardware circuit design, DSP software programming, experimental research on photovoltaic grid-connected strategy and MPPT algorithm, and analysis of the experimental results. The feasibility and effectiveness are verified.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615;TM464

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