Case Study of State Grid Corporation Photovoltaic Power Station and Analysis of Module-level Monitoring Data

In photovoltaic (PV) power station maintenance, low power generation efficiency and high energy loss have always been troublesome issues for maintenance personnel. Various factors such as abnormal modules, module shading, module accumulation, and MPPT (Maximum Power Point Tracking) failures can lead to low power generation efficiency. Conventional maintenance methods cannot effectively address these issues.Located in Jiande, Zhejiang Province, the State Power Investment Corporation’s 20MWp agrivoltaic power station adopted Fonrich’s module IoT and safety protection solutions. Over a period of two months, preliminary analysis identified the causes of low photovoltaic power generation. The detailed data analysis is presented below.

1. Power Generation Analysis

Total Power Generation：1762.27kWh

Total Lost Power Generation：174.54kWh

Percentage of Total Power Loss：9.9%

Average daily power generation loss of about 10%, significantly higher than the loss rate of ordinary PV power plants

2. Loss Type Analysis

Data analysis revealed that losses due to dust accumulation were relatively small, but module shading and inverter MPPT failures were significant. This indicates that the power station’s maintenance personnel were diligent in cleaning the station, but issues like module shading and MPPT failures could not be resolved through regular maintenance.

3. Module Abnormal Loss Analysis

Abnormal modules can lead to series losses. If the inverter’s MPPT inputs are paralleled, mismatches between series and parallel connections can cause losses. The heatmap below shows abnormal module losses. The darker the color, the more severe the abnormal loss. If the abnormal loss rate exceeds 10%, it is recommended to replace the modules to improve overall power generation.

Module Abnormal Loss Heat Map

4. Module Shading Loss Analysis

Shading will cause series losses within the string. If the inverter’s MPPT inputs are paralleled, mismatches between series and parallel connections can cause losses. The darker the color, the more severe the shading loss. If the shading loss rate exceeds 10%, it is recommended to address the shading issue to improve overall power generation.

Heat Map of Module Shadow Loss

5. Inverter MPPT Loss Analysis

Losses caused by mismatched series and parallel connections lead to MPPT losses; derated operation of the inverter can cause MPPT losses; aging and sampling distortion of the inverter can lead to MPPT losses. Inverter MPPT losses impact the overall power generation of the power station. If the inverter MPPT loss percentage exceeds 4%, it is recommended to replace the inverter.

Inverter MPPT Loss Ratio

6. Module Contamination Analysis

Dirty modules affect overall power generation. If the contamination rate of the modules exceeds 4%, it is recommended to clean the modules.

Heat Map of Module Contamination Loss

7. Benefits of Module IoT and Safety Protection

Module-level Data Reporting, Quickly Locate Faulty modules, Increase Power Generation, and Improve Maintenance Efficiency.

Fonrich’s photovoltaic safety data report provides detailed analysis of abnormal, shaded, and dirty modules, as well as inverter MPPT power losses, locating module positions, and greatly improving maintenance efficiency. Targeted adjustments can increase power generation.

Low-voltage Module Automatic Shutdown, Protects Modules and Increases String Power Generation.

When a module is abnormal or shaded, the module voltage drops, and the end module will actively shut down its output, eliminating the impact of abnormalities and shading on the string, protecting the modules, and improving string power generation.

Various Shutdown Methods for Station Safety.

Manual Shutdown:

• During rescue operations, manually shutting down the main control can reduce module voltage to 0V within 30 seconds.
• Rapid resolution of power generation faults by master control shutdown of problematic modules at regular intervals.

Automatic Shutdown:

• Display power off
• Disconnection
• Overheating
• Arc fault incident

Various fault detection solutions address power station maintenance challenges.

Arc Detection:

• Parallel arc
• String arc
• Arc fault location

8. System Diagram

System Solution