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Can The Inverter Be Able To Reduce Fire Hazard?
- May 15, 2018 -


What is the most feared of the PV power station? It's a fire, of course! Some time ago, the video of a photovoltaic plant fire was crazy on the Internet. Once again, the safety problem of the power station was mentioned above. Today we will talk about how to reduce or even eliminate potential fire hazards from the perspective of inverter.


As we all know, the DC side of photovoltaic power station is a serious disaster area for power plants. In the traditional photovoltaic system, there is a DC high voltage in the DC side of the photovoltaic power station, and the voltage is usually up to 600 - 1000V. The DC tension is easily caused by the loose contact points of the PV module, the bad contact, the damp of the wires and the breakdown of the insulation. DC arc will lead to a sharp rise in the temperature of the contact section. The continuous arc will produce a high temperature of 3000-7000 degrees centigrade, accompanied by high temperature carbonization around the device, the light fusing insurance, cable, and the heavy destruction of components and equipment caused fire. According to the well-known photovoltaic site statistics, in the fire of the photovoltaic power station, more than 80% of the fire in the power station is due to the fault of the DC side. The arc sparks caused by the DC high pressure are the "culprit" of the photovoltaic fire.


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Visible, in traditional photovoltaic system, DC high voltage brings great security risks. Especially in rooftop projects, DC arcing fires will affect buildings themselves and threaten the safety of personnel and property in buildings. Therefore, in the roof project, the safety of the photovoltaic power station is the primary concern. It needs to be considered from the angle of photovoltaic inverter equipment and the design angle of the photovoltaic power plant system (this article is temporarily not analyzed).


As shown in Figure 1, the micro inverse system provides a direct AC output inverter for each photovoltaic module. On the one hand, the photovoltaic components are completely decoupled to achieve accurate control of all components. On the other hand, the high voltage risk caused by the series of photovoltaic components is avoided. Compared with traditional photovoltaic systems, the micro inverse system has the following advantages in fire prevention for rooftop photovoltaic projects:



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Figure 1 micro inverse system diagram


As mentioned earlier, in the traditional photovoltaic system, the DC side photovoltaic cells are connected in series to form a 200V to 600V or even higher HVDC bus and then connect to the inverter. In the process of installation, it can easily cause the damage to the electrical shock of the engineers. In the long run, the insulation damage or the bad contact caused by the bad contact of the connecting parts is more important. Arc risk, arc temperature can reach thousands of degrees, causing fire, causing fire or personal injury.


At the same time, the traditional photovoltaic system also faces the following problems: the DC protection device is more expensive, lower than the reliability of the AC protection device, the high voltage DC arc is difficult to break off, the PV module is current source characteristics, the current will not significantly increase after over current, so the protection becomes more difficult; when the light is light, it is difficult to generate electricity, it is difficult to produce. Cut off, failure, especially after fire, pose a threat to rescuers and firefighters.


Can the inverters be selected to reduce the fire hazard in the end?

 

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Figure 2 system voltage contrast diagram


In the micro inverse system, because each photovoltaic module is connected to the inverter independently, the highest DC voltage of the system is the open circuit voltage of the photovoltaic cell, about 40V. It is very safe in the process of installation and use, without the risk of electric shock and arc firing, which fundamentally solves the problem of high DC voltage in the traditional system.


In summary, from the standpoint of inverter, the miniature inverter with low voltage and no DC arc risk can be said to be right without inverter.