摘要
光伏发电系统是空间电源的一种普遍形式,该系统的一个基本特点是太阳能输出功率受环境影响较大,由于光伏阵列输出特性的非线性特征,在不同的照射强度和温度下其I-V特性曲线各不相同,太阳能电池的输出曲线为非线性且为温度、日照强度与空间粒子辐照的函数,每一条曲线中所能画出的最大矩形面积则是Ipv与Voc的最大乘积值称为最大功率点,此点应为最佳工作点定义成Pmax,它所能输出的功率为最大。
目前国内空间电源系统对太阳电池发电的控制一般都采用CVT(恒压)的控制方式,太阳电池阵不能工作在最佳工作点,在初期会损失20%左右的能量。而采用峰值功率跟踪控制技术(MPPT)能随时跟踪太阳电池阵最大输出,充分利用太阳电池阵的能源,它的缺点是相对于CVT控制技术而言控制比较复杂,可靠性低,但随着电子技术的发展,这些缺点都能通过器件工艺克服。该项技术在NASA和俄罗斯卫星电源中均有应用,在国内还没有该项技术的应用。
本文介绍了太阳电池光伏特性、DC/DC变换工作原理、MPPT总体方案以及最大功率点跟踪算法,综合了空间电源的实际情况,采用了比较适合空间飞行器在轨飞行需求的扰动观察法与模糊自寻优设计方法相结合的方式对太阳电池最大功率点进行跟踪。在一个轨道周期内当搜索到最佳工作点后,改用经典的PI控制,锁定太阳电池最佳输出电压采用Buck降压的方式对镉镍蓄电池组进行充电。这样系统能实现最大限度的稳定运行,提高了可靠性。当到下一个轨道周期时重新启动MPPT程序,对太阳电池阵最佳工作点进行跟踪,搜索到最佳工作点后再用PI进行控制。然后到下一个轨道周期继续循环该过程。
MPPT控制系统硬件主要是DC-DC主回路模块和计算机控制模块。DC/DC采用Buck降压型转换电路。负载接在蓄电池组上,母线结构采用不调节母线,蓄电池组电压即为母线电压。回路中的各器件参数和设计值都考虑到工作环境的特殊性选择相应的达到军用标准的器件。采用单片机AT89C55作为主控制芯片,AT89C55具有低功耗、高性能的特点,它具有20K可重复编程的Flash。对多数嵌入式系统来说,AT89C55可以说是高灵活性和性价比的功能强大的控制芯片。
软件用单片机C语言进行编写,各控制环节的取值都考虑到系统稳定性和动态响应的要求,经过反复调试和试验,各控制环节的取值都能满足设计要求。
经过最终的测试,该系统在功能、电性能、反应速度、系统稳定性、可靠性等方面均能满足空间用电源系统的要求。在国内属于首个可以可以转入工程实际应用空间电源用MPPT系统。本文最后进行总结和展望,提出待改进之处。
Solar arrays are generally used to generate power for the space power system, the output of which is affected much by the circumstance situation. Since the output of solar arrays is non-linear, it will present different I-V curves according to different irradiation and different temperature, in another sense, the output of solar arrays can be seen as a non-linear function of temperature, solar irradiation and space particle irradiation. Of each curve, the maximum rectangular area, also the product of IPV and VOC is named as the maximum power point, and defined as Pmax, it will generate the most power.
The constant voltage technique (CVT) is widely used in domestic space power system, which means the solar can not work at the best power point bringing in an energy loss of 20%. While the maximum power point tracking technique (MPPT) can track the max power output of the solar cell on time, which can fully use the power generated by the solar array. Normally, the MPPT is more complicated and less stable compared to CVT. However, all these defects can be overcome through the development of electronic technology and the MPPT has already been used on the satellite of NASA and Russian rather than in China.
This dissertation introduced the characteristic of illumination-voltage curve, DC-converter’s principle, the general scheme and maximum power point tracking algorithm. The disturbance observation method and the fuzzy self-optimization method were combined to track the maximum power point of the solar cell, which is suitable for the space aircraft in orbit. If the best working point was found, the classic PI control method is taken into function, and the best voltage output of the solar cell is locked, meanwhile the Buck circuit will charge the Ge-Ni battery arrays. Such system can function with best stability and enhanced reliability. When satellite moves into next orbit cycle the MPPT program will be restart, tracking the best working point of solar array, taking PI control then repeating the process cycle after cycle.
The hardware of the MPPT system is composed of DC-DC main loop and the computer control module. Buck low voltage converter was used in DC/DC circuit, the load was connected to the storage cell, while the main bus took in the scheme without modulation which means the voltage of storage was that of the main bus. All the components were selected according to the special requirement of military and space standard. Monochip AT89C55 was chosen as the main control chip, which has the characteristic of low power consumption and high performance with a reprogrammable Flash of 20k. The AT89CC55 can be seen as a powerful control chip of high agility and cost-quality ratio, especially for embedded system.
The program was written in C, the parameters were set according to the stability and transient response requirement and the experimental results showed that parameters were chosen satisfyingly.
After the final test and measurement, this system was proven to satisfy the requirement of space power system in function, electricity performance, response rate, system stability and reliability. It is also the first MPPT system that can be transferred into actual space power application. The conclusion and expectation were presented at last; further improvement needed was also discussed.
引文
[1] 马世俊. 卫星电源技术. 北京:宇航出版社. 2001:1-10,12-32,336-373.
[2] 林珊,冯垛生.太阳能发电系统的最大功率跟踪控制.新能源,1999,21(2):25-27.
[3] 黄才勇.卫星电源的现状与发展动态综述(会议论文).总装备部卫星技术专业组.2002.
[4] 陈景贵.化学与物理电源.北京:国防工业出版社.1999:30-50.
[5] 赵福鑫,魏彦章.太阳电池及其应用.北京:国防工业出版社.1985:1-100
[6] 徐福祥.卫星工程.北京:中国宇航出版社.2002:180-194.
[7] 李惠增.空间电源技术与应用文集.上海航天技术研究院.2005:1-80.
[8] Pablo Rueda.SEGREGATED MAXIMUM POWER POINT TRACKING BASED ON STEP-UP REGULATION.ESA SP-589.2005.
[9] 欧阳名三,余世杰,沈玉.采用单片机的太阳能电池最大功率点跟踪控制器.《电子技术》.2002(8):25-28
[10]张占松,蔡宣三. 开关电源的原理与设计. 北京:电子工业出版社.2005:16-24.
[11]孙建平.太阳能电池最大功率点跟踪计算机控制.光电简讯.2001:21-25.
[12]淡军,孙茂相,杨继华.风电系统最大功率捕获的研究.沈阳工业大学学报 2003.
[13]史小平,许天舒.核电站热功率跟踪汽轮机负荷的动态矩阵控制仿真研究.中国电机工程学报.2001.
[14]孙佩石,何庆领.具有最大功率跟踪功能的光伏户用逆变电源.合肥工业大学学报(自然科学版).2001.
[15]王勇.太阳能电池最大功率跟踪及在光伏水泵中的应用.ENERGY ENGINEERING.2002.
[16]余世杰,何慧若,曹仁贤.光伏水泵系统中 CVT 及 MPPT 的控制比较.太阳能学报.1998.
[17]罗祥.高性能的光伏水泵专用型逆变器.太阳能学报.1997.
[18]Nafeh,Abd El-Shafy A.Fahmy, Faten H.Abou El-Zahab,EssamM. Evaluation of a proper controller performance for maxi mum-power point tracking of a stand-alone PV system. Solar Energy Materials & Solar Cells.2003.
[19]Hua, C.; Lin, J.. Renewable Energy An on-line MPPT algorithm for rapidly changing illuminations of solar arrays. An International Journal. 2003.
[20]Muhida, Riza; Park, Minwon; Dakkak, Mohammed; Matsuura, Kenji; Tsuyoshi Akira; Michira, Masakazu. A maximum power point tracking for photovoltaic-SPE system using a maximum current controller. Solar Energy Materials & Solar Cells,.2003.
[21]鄢婉娟.一种实现太阳阵峰值功率跟踪的智能控制方法.中国空间科学技术.1997.
[22]Abraham I.Pressman. Switching Power Supply Design.北京:电子工业出版社.2005:7-16.
[23]周志敏,周纪海.开关电源实用技术设计与应用.北京:人民邮电出版社.2005:105-116.
[24]Paul Horowitz,Winfield Hill.THE ART of ELECTRONICS. 北 京 : 电 子 工 业 出 版社.2005:96-140.
[25]赵修科.开关电源中磁性元器件.南京航空航天大学自动化学院.2004:106-110.
[26]李序保.电力电子器件及其应用.北京.机械工业出版社.1996:50-100.
[27]李华.MCS-51 系列单片机使用接口技术.北京:北京航空航天大学出版社.2000:3-100.
[28]薛钧义,张彦斌,MCS-51 系列单片机及其应用.西安:西安交通大学出版社.2001:10-50.
[29]赖寿宏.微型计算机控制技术.北京:机械工业出版社.2003:78-96.
[30]杨文龙.单片机原理及应用.西安:西安电子科技大学出版社.1999:1-150.
[31]康华光,陈大钦.电子技术基础(模拟部分).北京:高等教育出版社.1998:20-100.
[32]王幸之,王雷.单片机应用系统抗干扰技术.北京:北京航空航天大学出版社.2003:10-100.
[33]王俊普 智能控制 中国科学技术大学出版社 1996
[34]余世杰等.光伏水泵系统的最大功率点跟踪器[J].太阳能学报,1991, 2(3):225.
[35]张兴,张崇巍,孙本新.采用电流寻优的 MPPT 光伏阵列并网逆变器的研究.太阳能学报.2001.
[36]郑诗程,苏建徽,余世杰,沈玉樑.高效高性能光伏水泵专用变频器的研究与设计.电力设备网.
[37]Noguchi, Toshihiko; Togashi, Shigenori; Nakamoto, Ryo. Short-Current Pulse-Based Maximum-Power-Point Tracking Method for Multiple Photovoltaic-and-Converter Module System. IEEE Transactions on Industrial Electronics.2002.
[38]Wu, Tsai-Fu; Chang, Chien-Hsuan.Single-Stage Converters for PV Lighting Systems with MPPT and Energy Backup. IEEE Transactions on Aerospace & Electronic Systems.1999.
[39]Enslin, Johan H.R.; Wolf, Mario S. Integrated photovoltaic maximum power point tracking converter. IEEE Transactions on Industrial Electronics.1997.
[40]Thomson, Murray; Infield, David. Desalination A photovoltaic-powered seawater reverse-osmosis system without batteries. 2003.
[41]Masoum, Mohammad A.S.; Dehbonei, Hooman; Fuchs, Ewald F. Theoretical and Experimental Analyses of Photovoltaic Systems With Voltage- and Current-Based Maximum Power-Point Tracking. IEEE Transactions on Energy Conversion.2002.
[42]Calais, Martina; Hinz, Hartmut. Solar Energy A Ripple-Based Maximum Power Point Tracking Algorithm for a Single-Phase, Grid-Connected.1998.
[43]Hua, Chihchiang; Lin, Jongrong; Chihming Shen Implementation of a DSP-controlled photovoltaic system with peak power tracking. IEEE Transactions on Industrial Electronics.1998.
[44]张卫东.PID控制器自整定技术的发展---2002年世界控制大会总结报告.上海交大自动化系.
[45]Duarte J L, Wijntjens J A A, Rozenboom J. Designing light sources for solar powered system s [A]. P roc 5th Euro Conf Power Electronics and App l [C]. Brigh ton, U K: IEEE Press.1993(8):78-82.
[46]Snyman D B, Enslin J H R. Combined low cost, high efficient inverter, peak power tracker and regulator for PV application [A]. P roc IEEE PESC’89 [C]. Milwaukee, W I, U SA: IEEE Press.1989(1):67-74.
[47]马明建,周长城.数据采集与处理技术.西安:西安交通大学出版社.1998:12-56.
[48]Beukes H J, Enslin J H R. Analysis of a new compound converter as MPPT, battery regulator and bus regulator for satellite power system s [A]. P roc IEEE PESC’93 [C]. Seattle, WA, U SA: IEEE Press.1993:846-852.
[49]陈国呈.PWM 变频调速及软开关电力变换技术.北京:机械工业出版社.2002:5-64.
[50]阮新波,严仰光.直流开关电源的软开关技术.北京:机械工业出版社.2003:50-90.