Several Factors Affecting The Power Generation of PV Plants

Power generation is the benchmark for measuring the operating status of PV plants. For the same capacity PV plants, they might have much different power generation. Then how does the difference in the power generation capacity of the PV plant? And what factors will have a large impact on the power generation of the PV system?

‘Nobody can make bricks without straw’, many people regard power generation as the task of inverters. Actually, the PV panel is the only source of power generation.

The PV panel converts the energy radiated by sunlight into measurable direct current electricity through the Photovoltaic Effect. Without PV panels or the capacity of the panels is not enough, the system can not run normally even if the inverter is good. Therefore, choosing suitable and high-quality PV panels is critical for the PV system, it is also an effective guarantee for long-term stable income.

The design of the string has a great influence on the power generation of the system. With the same number of panels, the performance of the PV plant will be different when choosing different string designs.

Normally, the rated voltage of the three-phase inverter is generally around 600V. If the string voltage is low, the efficiency will be affected. Taking 56 pieces of 445Wp monocrystalline silicon modules with a 20KW inverter as an example, the power generation of string mode 2 is higher than that of string mode 1. Since the 19pcs panels per string will bring higher string voltage to realize the better performance of the system.

For the same PV panels in the same installation site, the orientation, inclination, and whether it is blocked will have an important impact on the power generation. Panel installations in the northern hemisphere are generally south-facing. In actual construction, even if the original roof is not facing south, the brackets will be used to make the panels face south to receive more light radiation during the year.

Theoretically, the installation inclination of the module should be close to or greater than the local latitude value, but it should also be designed according to the actual situation, and climatic factors such as roof load, wind resistance, wind, rain, and snow in a year should be considered. For larger rooftop power stations, it is recommended to use a smaller inclination angle.

In addition, in the plant design stage, all factors that may lead to occlusion must be considered in advance. Shadow occlusion can be treated as the biggest killer affecting power generation. If some panels in a string are blocked, even if only half a piece of them are blocked, there is almost no current. Therefore, during the installation, the obvious or potential blocking must be avoided.

What is "grid fluctuation"? It is a situation where the voltage value or frequency value of the power grid changes too much and too frequently, resulting in an unstable power supply to the load in the station area. Generally, a substation needs to supply power loads in many areas. Some terminal loads are even tens of kilometers away, and there is a loss in the transmission line. Therefore, the voltage near the substation will be adjusted higher. The PV system may be in standby mode because the grid voltage is raised too high. And if the PV plant is installed at the remote end, it may stop working due to Undervoltage. As long as the inverter is in standby or shut down state, the power generation will be reduced.

At the same time, the PV industry has continued to boom in recent years. In some areas where the mains voltage is normal, the voltage in this area might be increased due to the large proportion of the photovoltaic system capacity, and the absorption capacity in the area is limited. Then the photovoltaic systems themselves will also face the problem of grid fluctuations.

The power generation of the system is not only determined by the working state of the Inverter, but other issues such as the wiring state of different devices(inverter, PV panel, combiner box, etc), panel dust, cable aging, etc.

Problems in any part of the system will lead to abnormal operation of the PV plant, resulting in a reduction in power generation and revenue. Therefore, after the installation of the PV plant, during the system operation, it is necessary to grasp the dynamics of all aspects of the plant in real-time through online monitoring and regular site inspection, operation, and maintenance, and timely eliminate unfavorable factors that may affect the system operation to ensure the stable output of the PV plant.