There are many problems in the construction of photovoltaic power plants, such as dust accumulation, shading, attenuation, mismatch, and damage. Many investors therefore suffer huge losses and investment risks. Through power station quality services, such as site surveys, power generation assessments, key device adjustments and maintenance, etc., problems can be effectively discovered and solved to ensure the investment income of the power station. Among them, the power generation assessment service can meet the user's demand for the health status of the diagnostic power station.

Figure 1 Problems in the operation of the power station

Power generation assessment method

The so-called power generation assessment is based on the data collected at various stages of the PV power plant to establish a model, and the problems of the PV power plant are diagnosed by comparing and analyzing the differences between the power generation and the actual power generation. To do a good job in power generation assessment, there are mainly two steps: power generation simulation and difference analysis.

Fig. 2 Fit curve of active power and degree of illumination of power station

For power generation simulation, the first is the collection and input of environmental variables. By collecting actual measured environmental variables such as sensors, sinks, and inverters of photovoltaic power plants, the operation of the power plant can be more accurately understood. As shown in the figure, the total measured radiation curve of the power station and the peaks and valleys of the measured power generation on the day have a very precise fit, which provides a basis for fault diagnosis. The second is the model algorithm, which can be used to generate the power generation model of the power plant in combination with components, inverters, transformers, etc., and input the corresponding environmental variables into the corresponding power plant model, so as to obtain the ideal power generation amount under consideration of known environmental factors. Companies with rich data will use their own models modified through big data to reduce errors.

In terms of difference analysis, the ideal and actual measurement of power generation value, PR value, etc., can be compared to understand the actual difference between the actual amount of power generated by the photovoltaic power plant and the theoretical value. Through the corresponding comparison of each link (component, inverter, box change, etc.), the weak links of the power station can be specifically understood. This greatly simplifies the fault diagnosis of the power plant to a certain extent and refines the operation and maintenance management.

Long-term power generation assessment

The well-designed power station has its own monitoring system and complete and accurate historical environment data and power station operation data storage, which facilitates the operation diagnosis of the power station at different times. The high-end monitoring software integrates the power generation diagnosis function. According to the collection of the corresponding environment, components, inverters, combiner box and other parameters, automatic simulation analysis is performed and the loss ratio is displayed. At present, most of the monitoring systems are mainly collections of real-time data collection, simple analysis and alarm functions. This requires corresponding professionals to evaluate the data collected by the power station.

Power plant short-term power generation assessment

Figure 3 mobile monitoring toolbox body

China is currently in the early stage of intelligentization of photovoltaic power plants. Many power plants do not have a monitoring system installed, or they have monitoring systems that are not accurate and data collection is incomplete. The relevant details can be referred to in the seminar (click below to read the original). The result is that, on the one hand, because the power plant is not properly monitored due to improper operation and management, it faces problems such as component power attenuation, cracking, and PID. On the other hand, since the non-monitoring system cannot find the source of the problem, the power plant will be assessed for power generation. Bring great difficulties. At the same time, third-party quality inspection agencies also need their own power plant monitoring equipment to collect power plant parameters. So how to solve these problems?

Fig. 4 Meteorological sensors of mobile monitoring stations

In response to these problems, some companies have developed mobile data acquisition monitoring stations during the long-term operation and maintenance practice, which are more typical examples of mobile monitoring stations. The data monitoring station has the functions of sub-array data acquisition, environmental parameter collection, and power station diagnostics for photovoltaic power plants. Data collection for power stations for up to several weeks or months is achieved through the use of an external standardized high-accuracy sensitive sensor, a high-accuracy data collector, and a remote wireless communication system supported by it. The collected data is stored in the local mobile storage device or uploaded to the cloud through the network. The technicians can use the software or their own algorithms to analyze the data.

According to the needs of different users, this monitoring station can be flexibly configured to achieve different accuracy and functions. Of course, the mobile monitoring station can also be used to calibrate existing weather stations, sensors, and data acquisition systems of the power station to make it more accurate.

Figure 5 Mobile monitoring station setup

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