After finishing the installation and inspection of a photovoltaic system, the system will be ready to be connected into the grid to transfer energy. A process called system commissioning and PV commissioning is a process that requires a lot of attention to detail.So why do the inverters need commissioning?
Different countries have different regulations for inverter installations and the grid voltages of different countries are also quite complex. Inverters have a function to convert the electricity generated by solar energy into AC electricity with the same waveform and the frequency of grid, then supply the household load and feed the excess electricity into the grid.
We cannot distinguish between the electricity converted by the inverter and the electricity of the grid, because they are consistent. We need to adjust the inverter before it is connected to the grid, as it can match many grids. We need to find the one that meets Australian grid.
Here we must mention the power grid situation in Australia –
The Australian standard AS 60038 stipulates that the grid voltage is 230V +10% -6%, that is, 216V ~ 253V. Australia’s inverter standard states that if the voltage exceeds 255V for 10 minutes or once it exceeds 260V, it must disconnect itself from the grid. When these voltage standards are touched, the inverter will show tripping and “overvoltage” errors and will stop working.
We all know that the photovoltaic grid-connected system is the process of converting DC into AC through an inverter and transmitting it to the power grid. If the power grid is compared to the sea, the inverter can be regarded as a thin stream, and the grid connection is like a river trickling into the sea, the AC cable used for grid connection is the riverbed of the confluence.
In this regard, let’s make an analogy:
In some remote areas or weak grid areas, it is often necessary to raise the inverter output AC voltage (increases the river level, forming a high water potential to flow to the sea) due to the influence of line impedance (narrow riverbed, more blockages), in order to ensure that the AC power flows efficiently to the power grid (the river flows into the sea).
However, this will virtually cause two types of problems: First, the output voltage is higher than the inverter’s own protection voltage value, so the inverter reports errors and performs a protective shutdown; Second, the transformer capacity of the grid-connected point is small (that is, “insufficient water storage in the sea”, which is the reason why many places limit the grid-connected capacity), it is very likely to result in grid overload and raise the grid voltage (the reservoir water storage capacity is insufficient and overflowing).
In Australia, 60-70% of the area is rural, for the above reasons usually the grid voltage in the rural area will be higher than the rated voltage in the urban area, this may reach 260V. The inverter generally needs commissioning after installation to work normally.
Now there are two ways to adjust the inverter voltage, one is the screen adjustment and the other is to connect the inverter to the monitoring platform through Wi-Fi and adjust through the monitoring platform.
However, here is the reality that we have experienced –
The installation of the inverter needs to be cautious as it is a semiconductor-based electronic product, sensitive to external factors such as temperature, humidity and air pollution. The installation is more complex and professional, and in Australia it is necessary to have a licensed electrician to install the inverter. Labor cost is particularly expensive in Australia, and usually electricians’ hourly wages is as high as $43.64, or even higher. So, in Australia, electricians are very expensive in labor costs. Certified electricians often take several years of hard work to pass the examination of professionals. That means that the longer your inverter installation takes, the higher the labor costs, which requires the inverter to have the characteristics of rapid installation and adjustment, in order to be more effective in saving costs.
What the popular inverter brands have?
Sungrow, Huawei, and Aiswei only have a screen without keys, and Growatt has a screen without buttons, Goodwe has a screen with one button only. In this case, we cannot adjust inverters through the screen of the inverter
Let’s take a look at two companies that are good at that respect.
Both Solis and Each Energy have LCD screens and four-button adjustments, making it easy to do the commissioning after installation and no need of long press and short press, or tedious light flashing rules. In addition, the appearance of both machines is modern and sleek, especially for Each, which is small and delicate also, like a work of art.
The above brands all have the functions of monitoring through the Wi-Fi connection and adjusting on the platform, here we will not expand on the Wi-Fi connection for the time being. We will explain the Wi-Fi connection and monitoring interface in detail in the next episode.
In summary, products that can have both LCD screens and buttons, adjusting the parameters through this monitoring platform are more popular. During the actual installation we found that Solis with superior performance, needs to adjust the voltage and safety location with button adjustment, which will take some time. Each Energy has finished the safety setup according to the destination before the shipment, and the total adjustment time only needs one-fifth of Solis.