Common Faults and Solutions of Distributed PV Power Plants
**Chapter 1: Factors Affecting the Power Generation of Photovoltaic Plants**
The calculation method for power generation in photovoltaic (PV) plants is based on the formula: **theoretical annual power generation = annual average total solar radiation × total battery area × photoelectric conversion efficiency**. However, in reality, actual power output is always lower due to various factors that affect system performance. The actual annual power generation can be calculated as: **theoretical annual power generation × actual power generation efficiency**.
Understanding these influencing factors is essential for designing and maintaining an efficient PV system. Below are some key elements that impact the performance of a photovoltaic plant:
**1.1 Solar Radiation**
Solar modules convert sunlight into electricity, so the intensity of solar radiation directly affects power output. Accurate data on solar radiation can be obtained from sources like NASA’s meteorological databases or through PV design tools such as PV-SYS and RETScreen. These tools help estimate the potential energy yield of a system before installation.
**1.2 Tilt Angle of Solar Modules**
The tilt angle of the solar panels significantly influences the amount of solar radiation they receive. Most systems use a tilt angle close to the latitude of the location, but this can vary depending on the region. For example:
- Latitude 0° to 25°: Tilt angle equals the latitude.
- Latitude 26° to 40°: Tilt angle equals latitude + 5° to 10°.
- Latitude 41° to 55°: Tilt angle equals latitude + 10° to 15°.
Proper tilt ensures maximum exposure to sunlight throughout the year.
**1.3 Conversion Efficiency of Solar Modules**
The efficiency of solar modules determines how much of the incoming sunlight is converted into usable electricity. Higher efficiency modules can generate more power in the same space, making them ideal for installations with limited area.
**1.4 System Losses**
Over the 25-year lifespan of a PV system, components naturally degrade, leading to reduced efficiency. Additionally, several other factors contribute to system losses:
- **1.4.1 Mismatch Loss**: Differences in current or voltage between modules in series or parallel connections can cause significant power loss. To minimize this, it's important to use modules with similar electrical characteristics and ensure consistent degradation rates.
- **1.4.2 Dust Accumulation**: Dust can block sunlight and reduce the efficiency of the panels. It can also cause long-term damage if acidic or alkaline particles are present. Regular cleaning using sprinklers, manual methods, or robotic systems is recommended.
- **1.4.3 Temperature Effects**: As temperature increases, the efficiency of crystalline silicon modules decreases. A 1°C rise typically reduces power output by about 0.04%. Proper ventilation and cooling can help mitigate this issue.
- **1.4.4 Line and Transformer Losses**: Energy is lost during transmission through DC and AC circuits. These losses should be kept below 5% by using high-quality cables and ensuring tight connections.
- **1.4.5 Inverter Efficiency**: Inverters convert DC power to AC, and their efficiency plays a crucial role in overall system performance. String inverters usually operate at 97–98%, while centralized inverters can reach up to 98%.
- **1.4.6 Shading and Snow Cover**: Shadows from nearby structures or snow accumulation on panels can drastically reduce power output. Designing the system to avoid shading and clearing snow regularly is essential.
**Chapter 2: Common Faults of Distributed Photovoltaic Plants**
Distributed PV systems may encounter various issues that affect performance or even cause shutdowns. Here are some common problems and solutions:
**2.1 Inverter Screen Not Displayed**
If the inverter screen is not showing any information, check the DC input. Possible causes include low component voltage, reversed polarity, or open DC switches. Use a multimeter to measure the DC voltage and verify all connections.
**2.2 Inverter Not Connected to Grid**
This occurs when the inverter cannot connect to the power grid. Check the AC switch, output terminals, and wiring. If the AC voltage is not present, the problem could be with the grid connection or internal inverter fault.
**2.3 PV Overvoltage**
Excessive DC voltage can trigger alarms and stop the system. This often happens when too many modules are connected in series. Ensure the string voltage stays within the inverter’s acceptable range to prevent overvoltage.
**2.4 Isolation Failure**
Low insulation resistance between the PV system and ground can lead to safety hazards. Inspect all components, including junction boxes, cables, and connectors, for damage or water ingress.
**2.5 Leakage Current Fault**
High leakage current can indicate a fault in the system. Disconnect the PV array and check the AC grid. If the issue persists, contact technical support.
**2.6 Grid Error**
Abnormal grid voltage or frequency can cause the inverter to shut down. Use a multimeter to check the grid conditions. If the grid is unstable, wait for it to return to normal. Otherwise, reset the inverter after a period of disconnection.
**2.7 Inverter Hardware Failure**
Hardware faults can be recoverable or non-recoverable. In case of a hardware failure, disconnect all inputs and allow the inverter to power off for at least 30 minutes. If the issue remains, seek professional assistance.
**2.8 Low System Output Power**
Several factors can reduce system output, such as poor installation, shading, dust, or incorrect configuration. Ensure all components are properly aligned, clean, and wired correctly. Monitor the system regularly for optimal performance.
**Appendix: Selection Table for Grid-Connected Inverter AC Cables and Breakers**
For example, in systems where the AC cable length exceeds 50 meters, a thicker cable (e.g., 6 mm²) is recommended to reduce voltage drop. Shorter cables (2.5 mm²) can be used for distances under 50 meters. Always follow manufacturer guidelines to ensure safe and efficient operation.
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