Are you wondering what PID on PV modules is, how it manifests itself, and how damaging it can be? Would you like to find out what methods there are to identify it and how early can it be spotted? 如果PID在你的模块上得到确认，你应该怎么做? Below we try to answer all these questions and help you and help decide how to proceed.
光伏组件上的PID是什么?
电位诱导退化(PID) 对晶体硅来说最致命的问题之一是 薄膜太阳能电池板. That’s because it degrades the modules’ power output and reduces the performance ratio (PR) of solar plants. 虽然它最初并不表现为性能损失, 如果不及时处理，它会对性能产生巨大影响. 最终，它可能导致高达40%的功率损失.
更详细地解释PID到底是什么, 让我们从典型的光伏系统架构开始. 这 consists of strings of modules, connected in series to generate a high voltage. 出于安全考虑，各模块的框架均接地. 这 causes a potential difference between the cells and the outer part of the modules. The potential difference can lead to a leakage current between the modules’ silicon semiconductor and other module materials. 当这种情况发生时, the resulting potential-induced degradation causes the modules’ temperature to rise rapidly. 除非它停止了, 这将导致整个光伏系统的故障, 导致性能和产量损失. The likelihood for PID is exacerbated by the higher voltage strings that are now being used across the industry.
到目前为止，还没有针对PID的预测模型. 但是我们知道什么因素会影响PID是否会发生. 在模块级别, 这些包括封装材料, 电池上的抗反射涂层, 并对各模块进行了结构设计. 在系统级别, 而模块的框架是接地的, 逆变器一般不提供功能接地. As a result, a high potential difference between the modules’ cells and the frames is left floating. 这 initiates the PID-related degradation at mostly the negative end of the string, 虽然它也可能出现在积极的一端.
光伏组件电位诱导退化(PID)的图解.
你能在热成像检测中看到PID吗?
因为PID通常是均匀发展的, there’s often limited differential on the strings that would raise an alarm before yield loss occurs. 因为产量损失可能在多年后才会显现出来, 尽早识别PID是很重要的. 识别PID最有效的方法是 符合IEC 62446-3标准的航空热成像检测. 在温度记录, 传感器探测红外辐射, 温度在零度以上的物体都会发出什么. 因为模块的辐射会随着温度的升高而增加, pid引起的温度升高在热像仪上是可见的. 受感染的细胞比周围的细胞要热得多, 并且通常位于字符串的负端. 这 so-called ‘string-end heating pattern’ (SEHP) can be a sign of PID – but it doesn’t have to be.
Thermal inspection imagery of a 22-module string from an aerial thermographic inspection by 以上 – Modules 1, 3, 4, 5 and 6 exhibit multiple cells which are considerably hotter (more yellow) than other cells/modules and the affected modules are located at the end of a string. 这 so-called ‘string-end heating pattern’ (SEHP) is highly suggestive of PID.
如何判断SEHP是PID?
因为PID是太阳能站点的系统性问题, 当它确实出现时，它会以频率和一致性出现. If that isn’t the case, the identified SEHP may point to other issues that need investigating. It’s important not to classify an anomaly as PID because you cannot be certain with aerial thermography alone. 话虽如此, thermography can identify with very high certainty that there is an anomaly that requires further investigation. 进一步 地面测试 是否有助于验证和确认模块是否受到PID的影响. Established methods for this are Electroluminescence (EL) and current-voltage (I-V) curve measurements. Just to explain, EL refers to the light emitted by a material in response to an electric current. And I-V is a standard test to measure a module’s current-voltage characteristic.
PID是太阳能组件的一个系统性问题，进展缓慢. 这意味着你越早识别它, 你就越能成功地挽回局面.
受pid影响的光伏组件不同检测方法的比较. A，热成像图像(黄色越高表示细胞温度越高). b, 热成像图像(颜色较深表示细胞温度较高)和c, 电致发光图像(颜色较深表示细胞退化/失活).
当检查确认PV组件上有PID时该怎么办?
值得庆幸的是，带有PID的光伏组件可以恢复. 恢复过程的成功取决于，e.g.、模块类型、降解深度以及当地的湿度和温度. There is no one-size-fits-all solution, only individual solutions for each array.
One solution is to fit the array with so-called reversal boxes, also known as charge equalizers. The idea is to reverse the effects of PID over time and prevent it from continuing. 这 is done by putting a DC current through the module at night to reverse the PID. 但是，此澳门皇冠国际官方APP客户端并非100%完美，并且并非所有模块都可以恢复.
或者，可以添加浮动控制器来改变电位. 这些可以回顾性地安装到系统中，以防止进一步的PID发作. Any recovery through these measures will usually be evident within a few months. In this case, the reversal boxes stay on the array to reverse out the PID as it propagates. If the reversal doesn’t work, the next step is to submit a whole batch replacement warranty claim.
如果发生PID，如何开始保修索赔?
话虽如此, solar PV modules typically have a 10-year product warranty which covers product failure. 10年后，你可能会看到一个性能保证. 这, 然而, requires evidence that the module has declined in performance compared with what is expected after 10 years. 不幸的是, most in-field performance testing tools have a tolerance that is outside of what is required for successful warranty claims. Having data to provide evidence of degradation over time makes warranty claims more robust. (这就是标杆和 状态监测 进来. 我们在之前的博客文章中讨论过这个问题.)并且能够将一个序列异常细化到 特定模块批次 可以在你的保修索赔中增加重量吗.
如果您想了解更多有关此主题的信息，请下载我们的白皮书 “利用航空热像仪确定PID”.
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