基于光敏传感器的双轴太阳跟踪器的设计

译文及原稿译文题目 基于光学传感器光伏系统的单电机双轴太阳跟踪器的设计与实现原稿题目 Design and Implementation of a Sun Tracker with a Dual-Axis Single Motor for an Optical Sensor-Based Photovoltaic System原稿出处 Department of Electrical Engineering 基于光学传感器光伏系统的单电机双轴太阳跟踪器的设计与实现摘要 ：能源耗竭和全球气候变暖是地方发展的双重威胁，解决方法的最佳方式是利用可再生的能源资源。太阳能源是一种最有前途的可再生能源。太阳跟踪器可以大幅度提高电力生产。本文提出了一种新颖的利用的双轴太阳跟踪光伏系统的设计反馈控制理论以及四象限光电阻 (LDR) 传感器和简单的电子电路提供稳定的系统性能。 本文提出的系统采用独特的双轴交流电机和一个独立的光伏逆变器完成太阳能跟踪。 控制执行是一种简单而有效的技术创新设计。此外构造了一个按比例缩小的实验室原型来验证该计划的可行性。实验证实了太阳跟踪器的有效性。 最后，本研究结果可以作为未来太阳能应用的参考。关键词 ：双轴太阳跟踪器；太阳能光伏板；反馈控制理论的光依赖电阻器；独立光伏逆变器；能量增益1、介绍随着人口和经济的发展，能源危机的问题的快速增加和全球变暖影响今天是一个令人日益感到关注的话题。可再生能源资源的利用是解决这些问题的关键。太阳能是的主要来源之一清洁、 丰富和取之不尽，用之不竭的能源，这不仅提供了可替代能源资源，但也提高了环境污染。最直接的和技术上有吸引力地利用太阳能是通过光伏转换。 PV 电池 （也称为太阳能电池）的物理是非常类似于经典的 p— n 结型二极管。光伏电池将阳光直接转化为直流电（ DC ） 电力由光伏效应 [1， 2]。光伏面板或组件是光伏电池封装并相连为一体的装置。为了将太阳能电池板的功率最大化，一个需要保持的最佳的输出功率位置就是与一天中的太阳辐射相垂直。因此，配备太阳跟踪装置就变得很有必要。相对于固定的光伏组件，由太阳跟踪器驱动的光伏面板可以提高能量利用效率。太阳能跟踪是可以提高电力生产的光伏系统最合适的技术。要实现较高程度的跟踪精度，几种方法已广泛进行了研究。一般来说，可以列为要么基于太阳能的开环跟踪类型运动数学模型或使用传感器基于反馈的闭环跟踪类型控制器 [3 — 5]。 在开环跟踪方法， 跟踪公式或控制算法。谈到文献 [6-10] ，方位角和俯仰角，太阳角测定太阳运动的轨迹模型或在给定的日期、 时间和地理信息的算法。的控制算法在微处理器控制器 [11， 12] 被截止。 在闭环跟踪各种活动传感器设备， 例如电荷耦合器件 (Ccd) [13-15] 或光的方法依赖电阻器 （异地） [12,16-19] 被用于感受太阳的位置及反馈误差信号然后生成控制系统要不断收到的最大的太阳能辐射在光伏面板。本文提出了在这个问题上的实证研究方法。太阳能跟踪方法可以通过使用单轴式方案 [12,19-21] ，和双轴结构的高精度系统 [16 — 18,22 — 27]。一般来说，与单轴跟踪系统单自由度跟随太阳的运动从东到西白天时双轴跟踪也跟随太阳的仰角。近年来，双轴太阳跟踪系统已得到越来越多的研究关注。然而，在现有的研究中，其中绝大多数用两个步进电机 [22,23] 或 [16,17,24,25] 两个直流电动机来执行双轴太阳能跟踪。有两个跟踪电机的设计，两个电机装在垂直轴上，甚至在某些方向对齐它们。在某些情况下，两台发动机都在同一时间 [5] 不能动作了。此外，这类系统总是涉及使用微处理器芯片作为控制平台的复杂跟踪策略。在这项工作，只有单一的跟踪电动机，采用双轴企图取得了制定和实施一种简单而有效的控制方案。两轴间的阳光跟踪被允许在他们各自的范围内同时移动。利用常规电子线路，无需编程或计算机的接口。此外，提出的系统使用离网的光伏逆变器驱动电机，并提供电力供应。该系统是离网的和自主运行的。实验结果证明跟踪的可行性光伏发电系统并验证了提出的控制实现的优点。文章的其余部分按如下方式组织：第 2 节介绍了开发的闭环太阳跟踪系统，该系统基于传感器的反馈控制器使用的跟踪策略。太阳跟踪器硬件的详细结构在第 3 节中提出。在第 4 节，缩小实验室原型的建立和测试。最后，这项工作的主要结论描述在第 5 节。2、开发闭环太阳能跟踪系统开发的闭环太阳能跟踪系统的框图如图 1 所示描述组成和系统的互连。 闭环跟踪的方法，太阳能跟踪问题是如何使光伏面板位置 （输出），跟随阳光（输入） 尽可能地接近的位置。基于传感器的反馈控制器包含 LDR 传感器、 差分放大器和比较器。在跟踪操作中，低剂量辐射传感器测量阳光作为参考输入信号的强度。低剂量辐射传感器所产生的电压不平衡被放大，然后生成反馈误差电压。误差电压成正比阳光位置与光伏面板位置之间的差异。在这时间的比较将与指定的阈值 （公差） 误差电压进行比较。如果比较器输出变为高电平状态、 电机驱动和继电器被激活，旋转双轴 （方位角和俯仰角）跟踪电机和光伏面板给孙因此，反馈控制器执行的脸重要功能： 光伏面板和阳光不断地进行监测并发送微分控制信号来驱动光伏面板，直到误差电压小于预先指定的阈值。图 1.太阳能跟踪系统框图。系统会跟踪太阳高度自主的方位角和俯仰角角。整个工作图 2 和图 3 所示的流程图中，总结了算法。四个阳光的强度 LDR 基于传感电路测量不同的方向。电压 V E、 Vw、V S 和 V N 是定义为传感电压产生的东、 西、 南、 北的不同。在尝试从光伏面板、方位角和仰角跟踪过程可以得出最大功率同时继续进行直到光伏面板垂直正对在阳光下。该追踪器安装并不局限于地理位置。图 2.跟踪方位控制算法的流程图。 图 3.跟踪高程控制算法的流程图。3、太阳跟踪器的硬件设计图 4 给出了一个用于方位跟踪的太阳跟踪器的硬件电路图。整个系统具有两个方位方向和俯仰方向的双轴交流电机驱动的硬件电路。开发的太阳跟踪器由三个模块，是基 LDR的传感电路、 比较器和电机的驱动器与继电器。图 4.完全控制电路原理图的太阳跟踪器方位跟踪。3.1.基于 LDR 的传感电路若要跟踪阳光，就必须检测到到的位置，和太阳光电所需传感器。该太阳跟踪器使用光电传感器进行标定。 LDR 光敏电阻是可变电阻器的电阻取决于照在它上面的光照强度。电阻阻值随入射光强度增加而减小。 图 4 的第一部分中的 LDR 传感器是电压分压器电路的一部分，给出输出电压。3.1.1.太阳能的传感装置本文创建了一个使用光敏电阻与圆柱阴影太阳敏感器太阳跟踪器。图 5 显示了所设计的太阳能感应装置，包括一四象限 LDR 传感器和气缸安装在一块木板。太阳能感应装置连接到光伏板。东、西、南、北 LDR LDR 分别用于方位角运动和光伏面板的提升运动检测。基于阴影的光传感器的设计。如果光伏板不垂直于阳光，柱体的影子会覆盖一个或两个光敏电阻而产生不同的光照强度是由传感装置接收。 图 5.太阳能与四象限 LDR 传感器的传感装置。3.1.2.创建反馈误差电压在图 4 的第一部分，提出了一种用于创建偏差电压简单的电子电路。可以看出，分压器的输出电压会降低，当相应的 LDR 是阴影。如果一个传感器是亮的，另一种是阴影，差分放大器放大它们之间的电压差。反馈误差电压可以表示为：(1) 它可以重新排列，如下所示：(2) 如果西方 LDR 是阴影，3.2.比较器比较器的主要功能是充当一个开关来打开继电器和旋转电机。 A 比较器是本质上是一个运算放大器 （运放） 操作在开环配置中，将一个时变的模拟信号转换成二进制输出。第二部分中所示图 4，比较器被为了比较具有两个门限值的误差电压。的门槛值被定义为输入电压，输出的变化状态。如中所示图 4 有两个门限值，作为给出：比较器的输出是高饱和的状态 VH 或 VL 低饱和的状态。饱和VH 和 VL 的输出电压可分别接近电源电压 + VCC 和 -VCC 。的然后，如下所示表示产出的比较：比较器理想运算放大器的电压传输特性图 6 所示。 它注意到跟踪系统的灵敏度由是的阈值通过可变电阻 R4 跟踪精度调整。随着 R4 的减小，跟踪精度越高。然而，系统跟踪响应将变得越来越振荡。图 6.开环比较器电压传输特性。3.3.电机驱动与继电器图 4 的最后部分所示，它指出，电机驱动电路与继电器包括两个达林顿三极管对提供更多的电流增益和驱动继电器。 如果西方 LDR 是阴影， 反馈误差电压视图生成。 当 vEW > VTh1 > VTh2 ， 比较器输出 vpe 数据和 vPW 分别走高、 低饱和的电压。 晶体管 Q1 和 Q2 将因此， 行为和第 3 季度和 4 季度处于截止状态。 谈到图 4 晶体管 Q1 和 Q2 在提出主动模式中，操作和输入的电流或基极电流的 Q1 是：其中 VBE 是前偏基极 -发射极电压对双极晶体管。因此，输出当前可以写成：参数 1Β 和 2 β 是共发射极双极晶体管的电流增益。继电器被激活的输出电流，并通常开放接触 a1 关闭。在这种情况下，跟踪电机在方位方向顺时针旋转并因此光伏面板将向东移动到面对太阳。更具体地说，太阳跟踪器尝试调整光伏面板这样所有电压由异地几乎相等，并平衡。其结果是，光伏面板几乎是垂直于阳光下，具有高能源发电。4、结论本文介绍了一些简单功能和简单控件完成实现采用双轴交流电机的太阳跟踪器，跟随太阳和使用独立的光伏逆变器电源来支撑整个系统。提出的一个电机设计是简单和自包含的并不需要编程和计算机接口。已成功地建立和测试实验室原型验证控件实现的有效性。实验结果表明， 此系统增加了的发电量在晴间多云的天气下达到 28.31%。 本文提出的方法是到目前为止最为创新的。它实现了以下有吸引力的功能： （ 1）控制简单和符合成本效益。（ 2）独立的光伏逆变器电源支撑整个系统。（ 3）能够移动同时在其各自的范围之内，这两根轴。 （ 4）能够调整跟踪精度。 (5) 适用于移动平台上的太阳跟踪器。以上的实证研究结果使我们相信，这些研究工作能提供给我们一些好的太阳能产品开发的启示。Design and Implementation of a Sun Tracker with a Dual-Axis Single Motor for an Optical Sensor-Based Photovoltaic System Abstract: The dual threats of energy depletion and global warming place the development of methods for harnessing renewable energy resources at the center of public interest. Solar energy is one of the most promising renewable energy resources. Sun trackers can substantially improve the electricity production of a photovoltaic (PV) system. This paper proposes a novel design of a dual-axis solar tracking PV system which utilizes the feedback control theory along with a four-quadrant light dependent resistor (LDR) sensor and simple electronic circuits to provide robust system performance. The proposed system uses a unique dual-axis AC motor and a stand-alone PV inverter to accomplish solar tracking. The control implementation is a technical innovation that is a simple and effective design. In addition, a scaled-down laboratory prototype is constructed to verify the feasibility of the scheme. The effectiveness of the Sun tracker is confirmed experimentally. To conclude, the results of this study may serve as valuable references for future solar energy applications. Keywords: dual-axis Sun tracker; photovoltaic panel; feedback control theory; light dependent resistor; stand-alone PV inverter; energy gain 1.Introduction With the rapid increase in population and economic development, the problems of the energy crisisand global warming effects are today a cause for increasing concern. The utilization of renewableenergy resources is the key solution to these problems. Solar energy is one of the primary sources ofclean, abundant and inexhaustible energy, that not only provides alternative energy resources, but also improves environmental pollution. The most immediate and technologically attractive use of solar energy is through photo voltaic conversion. The physics of the PV cell (also called solar cell) is very similar to the classical p-n junction diode. The PV cell converts the sunlight directly into direct current (DC) electricity by the photovoltaic effect [1,2]. A PV panel or module is a packaged interconnected assembly of PV cells. In order to maximize the power output from the PV panels, one needs to keep the panels in an optimum position perpendicular to the solar radiation during the day. As such, it is necessary to have it equipped with a Sun tracker. Compared to a fixed panel, a mobile PV panel driven by a Sun tracker may boost consistently the energy gain of the PV panel. Solar tracking is the most appropriate technology to enhance the electricity production of a PV system. To achieve a high degree of tracking accuracy, several approaches have been widely investigated. Generally, they can be classified as either open-loop tracking types based on solar movement mathematical models or closed-loop tracking types using sensor-based feedback controllers [3 – 5]. In the open-loop tracking approach, a tracking formula or control algorithm is used.Referring to the literature [6– 10], the azimuth and the elevation angles of the Sun were determined by solar movement models or algorithms at the given date, time and geographical information. The control algorithms were executed in a microprocessor controller [11,12]. In the closed-loop tracking approach, various active sensor devices, such as charge couple devices (CCDs) [13 – 15] or light dependent resistors (LDRs) [12,16 – 19] were utilized to sense the Sun ’s position and a feedback error signal was then generated to the control system to continuously receive the maximum solar radiation on the PV panel. This paper proposes an empirical research approach on this issue. Solar tracking approaches can be implemented by using single-axis schemes [12,19– 21], and dual-axis structures for higher accuracy systems [16 – 18,22– 27]. In general, the single-axis tracker with one degree of freedom follows the Sun ’ s movement from the east to west during a day while a dual-axis tracker also follows the elevation angle of the Sun. In recent years, there has been a growing volume of research concerned with dual-axis solar tracking systems. However, in the existing research, most of them used two stepper motors [22,23] or two DC motors [16,17,24,25] to perform dual-axis solar tracking. With two tracking motors designs, two motors were mounted on perpendicular axes, and even aligned them in certain directions. In some cases, both motors could not move at the same time [5].Furthermore, such systems always involve complex tracking strategies using microprocessor chips as a control platform. In this work, employing a dual-axis with only single tracking motor, an attempt has been made to develop and implement a simple and efficient control scheme. The two axes of the Sun tracker were allowed to move simultaneously within their respective ranges. Utilizing conventional electronic circuits, no programming or computer interface was needed. Moreover, the proposed system used a stand-alone PV inverter to drive motor and provide power supply. The system was self-contained and autonomous. Experiment results have demonstrated the feasibility of the tracking PV system and verified the advantages of the proposed control implementation. The remainder of the article is organized in the following manner: Section 2 describes the tracking strategies of the developed closed-loop solar tracking system in which a sensor-based feedback controller is used. The detailed architecture of the Sun tracker hardware is proposed in Section 3. In Section 4, a scaled-down laboratory prototype is built and tested. Finally, the main conclusions of this work are drawn in Section 5. 2. Developed Closed-Loop Solar Tracking System The block diagram of the developed closed-loop solar tracking system is illustrated in Figure 1, describing the composition and interconnection of the system. For the closed-loop tracking approach, the solar tracking problem is how to cause the PV panel location (output) to follow the sunlight location (input) as closely as possible. The sensor-based feedback controller consists of the LDR sensor, differential amplifier, and comparator. In the tracking operation, the LDR sensor measures the sunlight intensity as a reference input signal. The unbalance in voltages generated by the LDR sensor is amplified and then generates a feedback error voltage. The error voltage is proportional to the difference between the sunlight location and the PV panel location. At this time the comparator compares the error voltage with a specified threshold (tolerance). If the comparator output goes high state, the motor driver and a relay are activated so as to rotate the dual-axis (azimuth and elevation)tracking motor and bring the PV panel to face the Sun. Accordingly, the feedback controller performs the vital functions: PV panel and sunlight are constantly monitored and send a differential control signal to drive the PV panel until the error voltage is less than a pre-specified threshold value. Figure 1. Block diagram of the solar tracking system. The system tracks the Sun autonomously in azimuth and elevation angles. The whole working algorithms are summed up in the flowcharts shown in Figures 2 and 3. The sunlight intensity from four different directions is measured by the LDR-based sensing circuit. The voltages vE, vW, vS and vN are defined as the sensing voltages produced by the east, west, south, and north LDRs respectively. In an attempt to draw maximum power from the PV panel, the azimuth and elevation tracking processes can simultaneously proceed until the PV panel is aligned orthogonally to the sunlight. The tracker installation is not restricted to the geographical location. Figure 2. Flowchart of tracking algorithm for azimuth control. Figure 3. Flowchart of tracking algorithm for elevation control. 3. Sun Tracker Hardware Design Figure 4 presents one of the hardware circuits of the proposed Sun tracker for azimuth tracking. The entire system has two hardware circuits with both of azimuth direction and elevation direction to drive the dual-axis AC motor. The developed Sun tracker is comprised of three modules, which are the LDR-based sensing circuit, comparator and a motor driver with a relay. Figure 4. Complete control circuit diagram of the Sun tracker for azimuth tracking. 3.1. LDR-Based Sensing Circuit To track the sunlight, it is necessary to sense the position of the Sun and for that an electro-optical sensor is needed. The proposed Sun tracker uses the electro-optical sensor for self-calibration. A LDR or photoresistor is a variable resistor whose electrical resistance depends on the intensity of the light falling on it. The LDR resistance decreases with incident light intensity increasing. As seen in the first part of Figure 4, the LDR sensor is a part of the voltage divider circuit in order to give an output voltage. 3.1.1. Solar Sensing Device The paper creates a Sun tracker using LDRs with a cylindrical shade as a Sun sensor. Figure 5 shows the designed solar sensing device, which comprises a four-quadrant LDR sensor and a cylinder mounted on a wood-block. The solar sensing device is attached to the PV panel. The East/West LDR and the South/North LDR are respectively used in the detection of azimuth motion and elevation motion of the PV panel. The design of the light sensor is based on the use of the shadow. If the PV panel is not perpendicular to the sunlight, the shadow of the cylinder will cover one or two LDRs and this causes different light intensity to be received by the sensing device. Figure 5. Solar sensing device with a four-quadrant LDR sensor. 3.1.2. Creating Feedback Error Voltage The simple electronic circuit for creating error voltage is presented in the first part of Figure 4. It can be seen that the output voltage of the voltage divider will be lower when the corresponding LDR is shadowed. If one sensor is lighted and the other is shadowed, the differential amplifier amplifies the difference voltage between them. The feedback error voltage can be expressed as: which can be rearranged as follows: If the west LDR is shaded,3.2. Comparator The main function of the comparator is to act as a switch to turn on the relay and rotate the motor. A comparator is essentially an operational amplifier (op-amp) operated in an open-loop configuration, which converts a time-varying analog signal into a binary output. As depicted in the second part of Figure 4, the comparator is designed to compare the error voltage with two threshold values. The threshold value is defined as the input voltage at which the output changes states. As shown in Figure 4, there are two threshold values which are given as: The output of the comparator is a high s