In an off-grid system with utility power complementation, there are two types of energy output sides, photovoltaic power generation and utility power. The load is energy consumption, and the battery can not only absorb electricity, but also release electricity for the load. Therefore, in the off-grid system, there are three sources of electricity for the load: mains, battery priority, and photovoltaic; there are also three battery charging modes: Electric charging, photovoltaic charging, mains and photovoltaic charging. The application scenarios and requirements of photovoltaic off-grid users are very different, so different modes should be selected according to the actual needs of users to maximize photovoltaics and meet customer requirements as much as possible.
PV priority mode
Working principle
PV gives power to the load first. When the PV power is less than the load power, the energy storage battery and PV together supply power to the load. When there is no PV or the battery is insufficient, if it detects that there is utility power, the inverter will automatically switch to Mains power supply.
Applicable scenarios
It is used in areas without electricity or lack of electricity, where the price of mains electricity is not very high, and in places where there are frequent power outages, it should be noted that if there is no photovoltaic, but the battery power is still sufficient, the inverter will also switch to the mains The disadvantage is that it will cause a certain amount of waste of electricity. The advantage is that if the mains power fails, the battery still has electricity and can continue to carry the load. Users with high power requirements can choose this mode.
Grid priority power consumption mode
Working principle
No matter whether there is photovoltaic or not, whether the battery has electricity or not, as long as the utility power is detected, the utility power will supply power to the load. Only after detecting the utility power failure, will it switch to photovoltaic and battery to supply power to the load.
Applicable scenarios
It is used in places where the mains voltage is stable and the price is cheap, but the power supply time is short. The photovoltaic energy storage is equivalent to a backup UPS power supply. The advantage of this mode is that the photovoltaic modules can be configured relatively less, the initial investment is low, and the disadvantages Photovoltaic energy waste is relatively large, a lot of time may not be used.
Battery priority mode
Working principle
PV gives power to the load first. When the PV power is less than the load power, the energy storage battery and PV together supply power to the load. When there is no PV, the battery power supplies power to the load alone. , the inverter automatically switches to the mains power supply.
Applicable scenarios
It is used in areas without electricity or lack of electricity, where the price of mains electricity is high, and there are frequent power outages. It should be noted that when the battery power is used to a low value, the inverter will switch to the mains with load. Advantages The photovoltaic utilization rate is very high, but the disadvantage is that the user's electricity consumption cannot be fully guaranteed. When the battery's electricity is used up, but the mains power just happens to be cut off, there will be no electricity to use. This mode can be selected for users who do not have particularly high power requirements.
The above three working modes can be selected when both photovoltaic and commercial power are available. The first mode and the third mode need to detect and use the battery voltage to switch. This voltage is related to the type of battery and the number of installations. , this voltage low point can also be set in the inverter. If there is no mains complement, the inverter has only one working mode, which is the battery priority mode.
There are also four ways to charge the battery. If you choose to charge the battery with the mains, you should notice that the efficiency will be reduced, because the mains will charge the battery and then discharge it, there will be a certain amount of power loss, usually off-grid inverter charging. The efficiency of discharge is about 90%, so there will be about 10% power loss.
Photovoltaic priority: Photovoltaic gives priority to charging the battery. Only when there is no photovoltaic, the mains will charge the battery. This mode is suitable for users whose mains electricity price is relatively expensive and the power supply requirements are not particularly high.
Mains priority: the mains will give priority to charging the battery, and the photovoltaic will charge the battery only when there is no mains. This mode is suitable for scenarios where the electricity price of mains is relatively cheap but frequent power outages occur.
Simultaneous charging of mains and photovoltaics: This mode is suitable for users with low mains electricity prices and high requirements for power supply.
Photovoltaic independent charging: no matter whether there is mains power, only photovoltaic charging is used. This mode is suitable for users with particularly high electricity prices and low power supply requirements.
The above four working modes can be selected when both photovoltaic and commercial power are available. If there is no commercial power complementation, the inverter has only one working mode, which is the photovoltaic independent charging mode.
Inverter.com offers two versions of off-grid solar inverters to complete your PV project. One version is a multi-function inverter / charger from 700 watt to 6000 watt, 12V/ 24V/ 48V DC input to 120V/ 220V/ 230V AC output, combining functions of inverter, and battery charger to offer uninterruptible power support with portable size. Another version is three phase pure sine wave inverter with high power from 8kW to 200kW, no battery storage design, smart LCD display setting, powerful protection functions.
