A. Background: In a residential rooftop project in China , the output power is low after the original 50 kW is expanded to 60 kW. The inverter of a certain brand is replaced with the Huawei SUN2000-60KTL-M0 inverter.
B. Log analysis: Analyze the inverter inspection logs provided by the customer.
1. The following 11 diagrams are the I-V curves obtained from inspection logs. The 12th diagram is the standard I-V curves of other projects for comparison.
2. According to the open-circuit voltage, PV modules 1–6 are one less than PV modules 7–11.
3. The curve of component 6 is the best, and the curves of components 5 and 8 are the worst. Curve 5 has obvious shadow effect. The Imp currents of all PV strings except PV string 6 decrease greatly.
4. When the temperature is fixed, the Imp current of the PV module changes with the irradiance, but the open-circuit voltage changes slightly. The higher the irradiance, the higher the output power of the module.
For example, when clouds suddenly pass through the sky, the output power of the component decreases because the cloud reduces the irradiance and the Imp decreases. As a result, the output power decreases.
C. Onsite check
1. PV modules are used as the roof onsite. The PV module angle is only 5° and there is a lot of dust on the PV modules.
2. There are poles in the south and block them at noon. It is verified that PV strings 5 and 8 in the log have shadow effects.
3. The SUN2000 outputs 380 V AC power and connects to the grid. A large number of grid overvoltage alarms and grid power failure alarms are generated in the SUN2000 alarm log.
D. Solutions
1. To reduce the inverter protection problem caused by high power grid voltage, perform the following steps to modify the parameters onsite:
Modify the protection parameters: SUN2000app --Special User --Password 00000a -- Set -- Protection Parameters-- Level-1 Overvoltage Protection Threshold --264 V
2. Clean PV modules periodically to increase the energy yield.
