李伟 - 文献翻译

1、 黄河科技学院毕业设计（文献翻译） 第 16 页太阳能阵列模拟器的设计和实现1.1太阳能阵列模拟器普及前景对于电力系统的卫星，地球上的太阳能电池阵列，有太阳能阵列模拟器是必要的，以便测试太阳能的性能和可靠性。基于太阳能电池的数学模型，本文设计了以实际的太阳能电池阵列模拟器，通过其可以生成太阳能电池的电流-电压特性。由于太阳能电池阵列模拟器的实现是以相同结构和权力作为真正的系统，所以它可以模拟出实际操作中大部分程度上真正的太阳能电池阵列。1.2太阳能阵列模拟器背景及目的太阳能是一种可再生能源，在住宅，光伏系统，交通，及航空航天工业中广泛使用。目前的空间力量领域，大多数卫星电源系统使用太阳能电池作

2、为它们的权力核心。卫星电源系统的性能直接影响卫星的性能和工作寿命。所以，为提高卫星电源的性能和可靠性，进行系统实时仿真和测试具有重要意义。太阳能电池阵列在太空工作中条件是非常重要的，因为阳光和温度变化迅速。依据电流-电压特性，可以测出每一个太阳能电池随光照和温度的参数。因此有必要模拟太阳能电池阵列的工作，在空间利用太阳能电池阵列模拟器(太阳能电池阵列模拟器，SAS)。进行此情景应用程序的主要任务是为各种供电子系统的卫星提供保障，同时允许测试卫星对地面的实际的太阳能电池阵列。2.1太阳能电池的数学模型等效电路通常用于光伏太阳能电池图1所示。这个电路由电流源、二极管串联电阻和并联电阻组成。图1太阳

3、能电池的等效电路根据一般二极管模型，二极管电流被描述为：I0是二极管饱和电流，VJ结电压，e是电子的电荷，n是二极管质量因素依赖于重组过程的结，通常在1和2之间的间隔，k是玻耳兹曼常数和T是温度。然后是太阳能电池的电流-电压特性：IPH光生成电流，我是输出电流，V是输出电压、串联电阻RS，RSh平行阻力。2.2太阳能阵列模拟器硬件设计常见问题根据数学模型和等效电路，太阳能电池的输出电流-电压曲线是一个指数曲线。它可以与电流源减去模拟二极管的电流-电压曲线。因此，太阳能电池可以模拟电路如图2所示： 图2一个太阳能字符串模块的示意图在这个电路中有两种反馈循环：电流反馈环和电压反馈循环。在目前的反馈

4、回路，IREF短路电流的参考，相当于照明，可以调整强度从0到100%。电压反馈回路，不洁净的开路电压引用对应的环境温度太阳能电池。当反馈电压小于不洁净的，放大器A1的输出是消极和二极管D1关闭。A2的输出只是确定IREF和输出电流是一个持续的短路电流。当反馈电压增加，A1的输出成为积极和二极管D1。A2的输出是由D1的电流，它增加了输出电压增加。因此，输出电压增加输出电流减少是根据二极管的电流-电压的特点。电压反馈回路中，不洁净的开路电压引用对应的环境温度太阳能电池。当反馈电压小于不洁净的时候，放大器A1的输出是消极和二极管D1关闭。A2的输出只是确定IREF和输出电流是一个持续的短路电流。当

5、反馈电压增加，A1的输出成为积极和二极管D1。A2的输出是由D1的电流，它增加了输出电压增加。因此，输出电压增加输出电流减少根据二极管的电流-电压的特点。图3太阳能电池阵列模拟器的框图每个字符串模块包括两个部分：上部和字符串较低的字符串，它们具有相同的电流-电压特性和串联连接。中心的龙头都是连接到一个分流器监管机构已与SAS相同数量的分支。的并联调节器是用来调节直流总线电压并使它稳定在一个预期的水平。并联调整器检测到总线电压与参考电压相比较； 区别是放大，给所有的分支机构。每一个部门包括PI调节器和一个晶体管，分流术多余的太阳能字符串的当前模块。如下示意图4中给出了并联调节器分支。图4并联调节

6、器分支示意图在这条赛道中，Verror实际直流总线之间的区别电压和基准电压。参考电压Vref每个分支逐渐增加了调节变量电阻VR1。放大器A1和A2由PI调节器，和晶体管Q1的收藏家是连接到中心抽头。当Verror小于Vref，PI调节器驱动Q1 这个监管机构分支机构不工作；当Verror更大然后它开始分路电流。3太阳能阵列模拟器控制系统SAS由30字符串模块，但一个工业标准底盘只能持有4字符串模块。所以4个模块及其相关控制电路安装在一个标准底盘和SAS包含8这样的单位。在SAS单元控制电路中，信号隔离电路和数据采集电路。基于高速单元控制电路ARM7处理器主要用于传输和转换数据。使用的AT91S

7、AM7S是Atmel的低的成员基于32位RISC引线数Flash微控制器处理器。它有一个64 k字节高速闪光灯和一个16 k字节SRAM，大量的外围设备，包括两个普遍的同步异步接收机收发器， 串行外围接口(SPI)等等。使其方便与PC机的串行端口和SPI它很容易驾驶系列广告和DA芯片。随着高速ARM7，单元控制电路接收从串行端口和解码数字控制命令很快，然后将它们转换成模拟信号。这些信号由信号隔离电路隔离，然后每一个字符串模块。字符串输出等模块状态电压、电流和温度也转移到单位控制电路由数据采集电路。结构SAS的单位，情景应用程序，分别由图5，图6所示；图5情景应用程序的结构单元图6情景应用程序框

8、图4仿真和实验结果4.1模拟设计为了验证前面设计的太阳能字符串模块，需要模拟出来，为此PSPICE模型建立了模拟电流-电压曲线。其仿真结果显示在图7和图8上，如下图7所示，短路电流随的强度照明Isc。当保持Voc和Isc不变增加，电流-电压曲线垂直变化。在图8中，开放电路电压随温度Voc。当保持Isc不变和Voc增加，电流-电压曲线变化水平。这些曲线对应的电流-电压特性(2)。图7与不同的照明模拟电流-电压曲线图8模拟电流-电压曲线具有不同的温度4.2 实验测试根据设计和模拟，建立2 kw SAS。来检查每个太阳能字符串的性能和电流-电压特性，许多实验数据被绘制不同的电流-电压曲线。结果是图9

9、和图10所示。在实验中，太阳能具有相同的Voc和Isc字符串模拟和仿真的电流-电压曲线非常接近结果。图9与不同的照明实验电流-电压曲线图10实验电流-电压曲线具有不同的温度4.3 实验比较为了验证情景应用程序的输出的一致性特点与实际的太阳能电池阵列，有必要测试，情景应用程序的单个字符串的电流-电压曲线和比较，太阳能电池的实际数据。显示实验结果如图11所示。图11电流-电压曲线在这个实验中，短路电流设置为1.16 ，开路电压是70 v。理论曲线计算与一个真正的太阳能电池的参数，使用太阳能电池的数学模型。可以看出SAS的电流-电压曲线实际的太阳能阵列的完美匹配。它证明了SAS 执行在模拟实际的太阳

10、能电池阵列。5结论本文依据一个实际的太阳能电池阵列模拟器为基础，提出了太阳能电池的数学模型。通过实验证明电流-电压特性的，并把情景应用程序非常类似于实际的太阳能数组中，所以它可以用来模拟复杂的操作条件下，真正的太空中太阳能电池阵列。由于模拟器具有实际太阳能电池阵列相同的输出力量和阵列结构，因此它可以用来模拟真实的卫星的电力系统。在未来，太阳能阵列模拟器可以作为实验平台，与其他子系统的卫星，从而支持其他子系统的地面测试。来源于： Design and Implementation of A Solar Array SimulatorAbstract-In order to test the pe

11、rformance and reliability of solar power system of satellites, solar array simulator on earth is needed. Based on the solar cells mathematic model, this paper designs a practical solar array simulator which can generate the solar cells I-V character. Since the implemented solar array simulator has t

12、he same structure and power as the real system, it can simulate the actual operating of a real solar array to most extent. Experimental results demonstrate the validity of this design which enables the further research on and diagnosis of solar power system.I. INTRODUCTIONSolar energy is a kind of r

13、enewable energy widely used in residential photovoltaic system, transportation, as well as in aerospace industry. In the present space power domain, most of the satellite power systems use solar cells as their power core. The performance of the satellite power system directly affects the satellites

14、performance and working life. So, in order to improve the performance and reliability of the satellite power system, real time simulation and testing is of great significance. Solar array in space works in very critical conditions, sunlight and temperature change rapidly. The I-V characteristic of e

15、very solar cell varies with illumination and temperature. Therefore it is necessary to simulate the solar arrays working conditions in space by using a solar array simulator (Solar Array Simulator, SAS). SAS's main task is to supply power for various subsystems on the satellite while permitting

16、the testing of the actual solar array of satellite on ground.II. THE MATHEMATICAL MODEL OF SOLAR CELLSThe equivalent circuit generally used for the photovoltaic solar cell is shown in Fig. 1. This circuit consists of a current source, a diode, a series resistance and a parallel resistance.Fig. 1. Th

17、e equivalent circuit of the solar cellAccording to general diode model, the diode current can be described asWhere I0 is the diode saturation current, VJ is the junction voltage, e is the charge of electron, n is diode quality factor dependent on the recombination processes in the junction, usually

18、from the interval between 1 and 2, k is Boltzmanns constant and T is temperature.Then the I-V character of solar cells isWhere IPH is light generated current, I is output current, V is output voltage, RS is series resistance, RSh is parallel resistance.III. HARDWARE DESIGNAccording to the mathematic

19、al model and equivalent circuit, the output I-V curve of the solar cell is an exponent curve. It can be simulated with a current source minus a diodes I-V curve. Therefore, the solar cell can be simulated with the circuit shown in Fig. 2.Fig. 2. The schematic of a solar string moduleIn this circuit

20、there are two feedback loops: a current feedback loop and a voltage feedback loop. In the current feedback loop, IREF is the short circuit current reference, corresponds to the intensity of the illumination and can be adjusted from 0 to 100%. In the voltage feedback loop, TREF is the open circuit vo

21、ltage reference which corresponds to the ambient temperature of the solar cell. When the feedback voltage is less than TREF, the amplifier A1s output is negative and diode D1 turns off. Then A2s output is only determining by the IREF and output current is a constant short circuit current. When the f

22、eedback voltage increases, A1s output becomes positive and diode D1 turns on. A2s output is determined by D1s current, it increases with the output voltage increases. So the output voltage increases with the output current decreases according to the diodes I-V characteristic.In order to simulate the

23、 real satellite power system, a solar array simulator is built up with 30 identical string modules. The block diagram is shown in Fig. 3.Fig. 3. The block diagram of solar array simulatorEvery string module includes two parts: upper string and lower string, they have the same I-V characteristic and

24、are connected in series. All the center taps are connected to a shunt regulator which has the same amount of branches with SAS. The shunt regulator is used to regulate DC bus voltage and make it stable in an expected level. The shunt regulator detects the bus voltage and compares it with the referen

25、ce voltage; the difference is amplified and given to all the branches. Each branch includes a PI regulator and a transistor, which shunts redundant current of a solar string module. The schematic of a shunt regulator branch is given in Fig. 4.Fig. 4. a shunt regulator branch schematicIn this circuit

26、, Verror is the difference between actual DC bus voltage and reference voltage. The reference voltage Vref of each branch is gradually increased by adjusting the variable resistance VR1. Amplifier A1 and A2 consists of a PI regulator, and the collector of transistor Q1 is connected to the center tap

27、. When Verror is smaller than Vref, the PI regulator drives Q1 off and this regulator branch doesnt work; when Verror is bigger then it works and begins to shunt current.IV. CONTROL SYSTEMThe SAS consists of 30 string modules, but an industrial standard chassis can only hold 4 string modules. So 4 m

28、odules and their releted control circuits are mounted in a standard chassis and a SAS contains 8 such units. In a SAS unit there are a unit control circuit, a signal isolation circuit and a data acquisition circuit. The unit control circuit based on a high speed ARM7 processor is mainly used to tran

29、sfer and convert data. The AT91SAM7S used is a member of Atmels low pin-count Flash microcontrollers based on the 32-bit RISC processor. It features a 64k byte high-speed Flash and a 16k byte SRAM, a large set of peripherals, include two universal synchronous asynchronous receiver transceiver (USART

30、), a serial peripheral interface (SPI) and so on. The USART makes it convenient to be connected with PCs serial port and SPI makes it easy to drive serial AD and DA chips.With the high speed ARM7, the unit control circuit receives digital control commands from serial port and decodes it quickly, the

31、n converts them to analog signals by DA. These signals are isolated by the signal isolation circuit and then given to every string module. String module states such as output voltage, current and temperature are also transferred to unit control circuit by data acquisition circuit. Fig. 5 is the stru

32、cture of a SAS unit. The SAS is controlled by an industrial PC. In order to control 8 SAS units by serial ports, a master control board is developed to extend serial port. The master control board also based on an ARM has two serial ports, one port is connected with the computer and the other is con

33、nected with 8 units which forms a master-client structure. It transfers control commands to 8 units and gets unit states by polling mode. The SAS block diagram is hown in Fig. 6.Fig. 5. structure of a SAS unitV. SIMULATION AND EXPERIMENT RESULTSA. SimulationIn order to verify the previously designed

34、 solar string module, a PSPICE model is built up to simulate the I-V curve. The simulation results are shown in Fig. 7 and Fig. 8. As is shown in Fig. 7, the short circuit current varies with the intensity of the illumination Isc. When keeping Voc unchanged and Isc increased, the I-V curve verticall

35、y shifts up. In Fig. 8, the open circuit voltage varies with the temperature Voc. When keeping Isc unchanged and Voc increased, the I-V curve shifts right horizontally. These curves correspond to the I-V characteristic given in (2).Fig. 7. simulated I-V curves with different illuminationFig. 8. simu

36、lated I-V curves with different temperatureB. ExperimentsBased on the design and simulation, a 2kw SAS is built up. To examine every solar strings performance and I-V characteristic, many experimental data has been taken to draw different I-V curves. The results are shown in Fig. 9 and Fig. 10. In t

37、he experiments, the solar string has the same Voc and Isc with the simulation, and the I-V curves are very close to the simulation results.Fig. 9. experimental I-V curves with different illuminationFig. 10. experimental I-V curves with different temperatureC. ComparisonIn order to verify the consistency of the SASs output