光伏发电最大功率点追踪及与市电联合供电策略研究

发布时间：2018-07-29 08:00

【摘要】：目前光伏电池光电转换效率较低,其输出功率更受到环境温度和光照强度的制约。为提高光伏系统综合利用率,需在光伏电池与外部负荷之间施加性能优良的最大功率点追踪(Maximum Power Point Tracking,MPPT)控制策略;另一方面,因受重庆地区多云雾、寡日照气候影响,光伏输出功率的波动性和间歇性很大,为保证电负荷稳定运行,有必要引入蓄电池组作为能量缓存设备,并引入外部电源作为光伏发电系统的补充电源。首先,本文在Matlab中建立光伏电池数学仿真模型,并分析了光伏电池的P-U输出特性曲线,在此基础上提出基于初值设定双模式电导增量法(INC)的光伏MPPT控制算法;然后,对本文所提算法进行数学推导,分析了光伏电池开路电压Uoc与光照强度S的关系以及参考电压初值设定对MPPT追综速度的影响;其次,设计了硬件实现电路并进行了实验验证。再次,针对重庆地区,为弥补其离网式光伏发电系统自身缺陷,本文设计了光伏-市电联合供电系统;最后,对其结构进行说明并给出了切换电路,在阻性负载下对切换控制策略进行了实验。实验结果表明:(1)计算机辅助仿真环境下,光照度两次突变时,本文所提MPPT控制策略追踪时间分别为0.27s和0.15s,追综效率MPPT达98.72%;与未加本文控制策略的光伏系统相比,电能提高百分比MPPT为6.09%,验证了本文所提算法的正确性。(2)室内精确可控环境下,与未施加本文控制策略相比,本文所提MPPT控制策略在弱光照下MPPT达3.90%、追综效率MPPT为95.69%;在强光照下MPPT达3.72%,追综效率MPPT为97.82%;环境突变条件下,施加本文控制策略后,追踪时间提高0.98s,MPPT达3.67%,追综效率MPPT为95.87%。表明本文所提MPPT控制策略的环境适应性较强且减少了稳态震荡。(3)室外环境下进行交叉验证实验,结果表明:与未施加本文控制策略相比,本文所提MPPT控制策略在启动性能、动态性能以及负载突变情况下的性能均得到改善,追踪时间缩减,抗干扰能力增强,对光伏工程应用具有一定的指导意义。(4)设计并制作了一套"光-储-市电"联合供电系统,实验结果表明,在联合供电控制策略下,系统可实现供电电源的稳定切换,切换时间小于0.7s,电能质量和切换时间符合GB/T14048.11-2002《自动转换开关电器》国家标准;最后,评估了联合供电系统的运行经济效益。
[Abstract]:At present, photovoltaic cells have low conversion efficiency and their output power is restricted by ambient temperature and light intensity. In order to improve the overall utilization rate of photovoltaic system, the best power point tracking (Maximum Power Point control strategy should be applied between photovoltaic cell and external load. On the other hand, because of the cloud and fog in Chongqing, the climate has little sunshine. The fluctuation and intermittency of photovoltaic output power is very large. In order to ensure the steady operation of electric load, it is necessary to introduce battery as energy buffer equipment and external power supply as supplementary power source for photovoltaic power generation system. Firstly, the mathematical simulation model of photovoltaic cell is established in Matlab, and the P-U output characteristic curve of photovoltaic cell is analyzed. Based on this, a photovoltaic MPPT control algorithm based on initial value setting double mode conductance increment method (INC) is proposed. The mathematical derivation of the algorithm proposed in this paper analyzes the relationship between the open circuit voltage (Uoc) of photovoltaic cells and the illumination intensity S and the effect of the initial value of reference voltage on the capping speed of MPPT. Secondly, the hardware implementation circuit is designed and verified by experiments. Thirdly, in order to make up for the defects of off-grid photovoltaic power generation system in Chongqing area, this paper designs a photovoltaic / municipal power supply system. Finally, the structure of the system is explained and the switching circuit is given. The switching control strategy is tested under resistive load. The experimental results show that: (1) in the computer aided simulation environment, the tracking time of the proposed MPPT control strategy is 0.27s and 0.15s, and the MPPT is 98.72.Compared with the photovoltaic system without the proposed control strategy, the tracking time of the proposed control strategy is 0.27s and 0.15s, respectively. The percentage of electrical energy increase MPPT is 6.09, which verifies the correctness of the algorithm proposed in this paper. (2) compared with the control strategy without the proposed control strategy, the proposed algorithm is more accurate and controllable in the indoor environment. The MPPT control strategy proposed in this paper has a MPPT of 3.90 and an efficiency of 95.69 under weak light, a MPPT of 3.722 and an efficiency of 97.82 under strong illumination. Under the condition of environmental mutation, the tracking time is increased by 0.98 s and the tracking efficiency MPPT is 95.87 after applying the control strategy. The results show that the proposed MPPT control strategy is more adaptable to the environment and reduces the steady state oscillation. (3) Cross validation experiments are carried out in outdoor environment. The results show that compared with the proposed MPPT control strategy, the performance of the proposed MPPT control strategy is better than that of the proposed control strategy. The dynamic performance and the performance of the load sudden change are improved, the tracking time is reduced, and the anti-interference ability is enhanced. (4) A set of "optical-storage-electricity" combined power supply system is designed and manufactured, which has certain guiding significance for the application of photovoltaic engineering. The experimental results show that under the joint power supply control strategy, the system can realize the stable switching of power supply, the switching time is less than 0.7 s, the power quality and switching time conform to the national standard of GB/T14048.11-2002. The economic benefit of the combined power supply system is evaluated.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615

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