The accelerated increase in the number of photovoltaic systems installed in Brazil and around the world has raised attention to the issue of the safety of these systems.
Traditional photovoltaic systems operate at high voltages of several hundred volts. In addition to electric shock, there is a risk of electric arcing in direct current circuits – that is, in the circuits that make the series and parallel connections of the photovoltaic modules.
Once an electric arc originates, it is difficult to extinguish it as it is not possible to turn off the photovoltaic modules, as it is not possible to remove their power source: sunlight.
Electrical arcs can cause fires that are difficult to resolve, with the aggravation of the presence of dangerous voltages, which put rescue teams at risk.
The main causes of electric arcs and fires are poor connections in DC circuits. A faulty connector or a poorly tightened screw can result in a fire in the photovoltaic system.
Solution to the risks of fire and electric shock
The industry has been working to provide technological solutions that allow mitigating the risks existing in photovoltaic systems.
Two main solutions have been proposed. The first is the use of power optimizers associated with rapid shutdown systems.
This technology makes it possible to individualize the photovoltaic modules of the strings and allows them to be turned off, reducing their output voltage to a few volts, in the event of an electric arc, which requires the combined use of an electric arc detection system, known as AFCI. – arc fault circuit interrupter.
The second solution is the use of microinverters in photovoltaic systems. Microinverters receive a small number of photovoltaic modules, usually one or two modules per MPPT input, and thus eliminate the need to connect modules in series and form strings. This naturally reduces the voltage levels present in photovoltaic systems, avoiding the risk of electric shock, arcing and fire.
In addition to the safety-related advantage, the use of microinverters also facilitates the installation of photovoltaic systems, making it closer to something like “plug-and-play”, avoiding the use of direct current cabling, stringboxes and switching devices and protection that are normally used in photovoltaic systems with strings.
The microinverter is quite different from the traditional inverter. Its main difference is that on the DC side only a fixed number of photovoltaic modules can be connected, depending on the number of input connections the equipment has.
In recent years, the industry has introduced many innovations that have increased the power of photovoltaic modules available on the market. It is now possible to find modules with powers above 700 W and short-circuit currents that are already close to 20 A. This has forced the updating and advancement of microinverter technology.
In this article, the TSUN will present in detail its new Titan microinverter and describe the features and advantages of its product for photovoltaic systems.
How to choose a suitable micro inverter?
Domestic systems in Europe (410 W module)
According to installation requirements, the size of photovoltaic modules is limited in Europe.
As a result, the modules used in distributed generation systems are mostly in the 400 to 450 W range.
Take as an example the series VERTEX-S by Trina Solar, which has its parameters presented in the table below.
In the STC condition, the peak power of the largest module in the series is 410 W, the open circuit voltage is 41,6 V, and the short circuit current is 12,4 A.
For this type of PV module, we recommend TSOL-MS3000 microinverter from TSUN's new TITAN series, whose parameters are shown in the following table.
The TSOL-MS3000 has 4 independent MPPT inputs, each prepared to receive two modules in series – in total, the equipment can operate with 8 photovoltaic modules, as shown in the following figure.
The open circuit voltage of each input is 83,2 V, which is a low safety voltage that does not pose a shock or arc flash hazard.
Taking TSM-410 as an example, the total input power of 8 modules is 410W * 8 = 3280W, while the nominal output power of TSOL-MS3000 is 3000W. In this case, the oversizing of PV modules is close to 1,1.
Home system in South America (550 W module)
Sunshine is abundant in South America, and the power of the most common photovoltaic modules on the market is currently in the range of 500 to 550 W.
Take Longi's Hi-Mo 5m series as an example, whose characteristics are shown in the following table.
In the STC condition, the peak power of the highest power module is 550 W, the open circuit voltage is 49,8 V, and the short circuit current is 13,98 A.
For this type of module we recommend the TSOL-MP3000 microinverter from TSUN's new TITAN series, whose parameters are shown in the following table.
The TSOL-MP3000 has 6 independent MPPT inputs, allowing it to operate with up to 6 photovoltaic modules.
Taking Longi's LRS-72HPH-550M module as an example, the total input power of the modules is 550 W * 6 = 3300 W, while the rated output power of the TSOL-MP3000 is 3000 W. In this case, oversizing of photovoltaic modules is 1,1.
Small industrial and commercial projects (modules greater than 600 W)
Considering the safety requirements of some particular customers (such as gas stations and classified areas in general), microinverters can also be used in industrial and commercial projects.
And industrial and commercial projects mainly use high-power photovoltaic modules of around 550 to 700 W.
For example, we can analyze the characteristics of Trina Solar's 670W Vertex series. In the STC condition, the peak power of the PV module is 670 W, the open circuit voltage is 45,7 V, and the short circuit current is 18,5 A.
For this type of module we also recommend the TSOL-MP3000 microinverter from TSUN's new TITAN series, whose parameters have already been shown in the previous table.
The maximum input current supported by the TSUN MP3000 microinverter is compatible with the photovoltaic module with 210 mm cells, as is the case with the module shown.
Considering the use of 6 modules at the input, we have a peak power of 670 W * 6 = 4020 W, while the nominal output power of the TSOL-MP3000 is 3000 W. In this case, the oversizing of the photovoltaic modules is 1,3. XNUMX.
At the same time, TSOL-MP3000 can also support other high-power PV modules, considering oversizing in the range of 1,2-1,4 according to different PV projects.
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