When choosing a household photovoltaic energy storage inverter system, there are some functions that are not explicitly introduced in the inverter parameters or manuals, but they are very meaningful for practical applications. CDS solar mainly introduces the following functions:
01 Unbalanced output function
In the application scenarios of three-phase household electricity in Germany, Austria, and other industrial and commercial applications such as shopping centers, parking lots, and stations, three-phase photovoltaic energy storage systems are usually the best choice. However, to supply power to single-phase loads in the system, different sizes of electrical energy need to be transmitted on each phase. We call it the ‘unbalanced output function’.
In the scenario of anti backflow, if the upstream power control is phase by phase (single-phase level control), then the unbalanced output function will be crucial, as the upstream power on each phase will be limited separately. This requires the inverter to be able to output different power based on the load consumption of each phase.
100% unbalanced function
100% unbalanced output refers to the range of output power per phase from 0W to 1/3 of the inverter’s nominal power, and the maximum difference in output power per two phases can also reach 1/3 of the inverter’s nominal power.
In order to achieve unbalanced output, smart meter with CT function is usually used to monitor the load consumption of each phase in real-time operation, so that the inverter can adjust the output power of each phase accordingly.
02 Seamless switching during power outage
The off-grid output capacity or backup power supply capacity is an important function of photovoltaic energy storage systems. Especially in situations where the public power grid is unstable or important household loads require uninterrupted power supply. In this case, the energy storage inverter should also have off-grid output capability and seamless switching capability from grid connected state to power outage state.
The seamless switching capability is usually achieved through integrated bypass circuits rather than external switches or relays, as it is difficult to synchronize the operation between the optical storage system and external devices.
Level switching
UPS level off grid switching means that the switching time from grid connected mode to off grid mode of the backup power supply is less than 10ms, which is the time that most ordinary household loads can traverse without cutting off the power supply.
For important loads such as emergency lights, fans, or life-saving equipment, the UPS level switching time is very important.
03 Remote control
Photovoltaic systems typically require long-term and continuous operation and maintenance services. Nowadays, a 10-year warranty is very popular worldwide, so convenient operation and maintenance solutions are very important in energy storage inverter systems. The remote control function can greatly reduce the time cost of on-site after-sales service and the cost of the service itself.
Remote control functions typically include:
Obtain system operation logs for necessary analysis
Remote upgrade of energy storage inverter firmware version
Configure system settings such as working mode, power limit, etc
Remote upgrade of battery BMS through inverter
At present, lithium-ion batteries in the market also tend to achieve remote upgrade functions, some of which are completed through the battery’s own network connection. Some can also be achieved through communication with the inverter, but this requires synchronization support between the inverter and the battery.
04 Protocol matching
Generally speaking, a photovoltaic energy storage system is a combination system that integrates all the equipment in the entire photovoltaic storage system, including batteries, photovoltaic modules, inverters, brackets, meters, control systems, etc. Inverter manufacturers are clearly unable to provide all the equipment required for the entire energy storage system. In a complete optical storage system, it may also need other components to achieve intelligent energy management, including EMS controller, multi-function smart meter, thermal controller, pump controller, etc., to ultimately maximize the PV self use rate or specific load control.
With the development of the energy storage industry, energy storage systems may need to be upgraded. This means that the energy storage inverter should be compatible with general protocols such as Modbus TCP, Modbus RTU, SUNSPEC, etc. In addition, it is best for inverters to have scalability in order to be compatible with other protocols in the future.
Photovoltaic energy storage systems are not just about charging and discharging batteries. Within five to ten years after the completion of the energy storage system, new functional requirements will emerge for the energy storage system, and the energy storage inverter product itself will continue to adapt to these changes.
