01 Cost comparison: DC coupling includes controllers, bidirectional inverters, and switching switches; AC coupling includes grid connected inverters, bidirectional inverters, and distribution cabinets. From a cost perspective, controllers are cheaper than grid connected inverters, and switching switches are also cheaper than distribution cabinets. The DC coupling scheme can also be made into a control inverter integrated machine, which can save equipment and installation costs, so the cost of the DC coupling scheme is lower than that of the AC coupling scheme.

02 Applicability compared to DC coupling systems, where the controller, battery, and inverter are serial and tightly connected, but have poor flexibility. The AC coupling system, grid connected inverters, batteries, and bidirectional converters are parallel, not tightly connected, and have good flexibility. If an installed photovoltaic system requires the installation of an energy storage system, AC coupling is relatively good. As long as a battery and bidirectional converter are installed, it will not affect the original photovoltaic system, and the design principle of the energy storage system is not directly related to the photovoltaic system, which can be determined according to the needs. If it is a newly installed off grid system, the photovoltaic, battery, and inverter should be designed based on the user's load power and electricity consumption, and a DC coupling system is more suitable. However, the power of DC coupling systems is relatively low, usually below 500kW, and larger systems are easier to control with AC coupling.

03 Efficiency Comparison

From the perspective of photovoltaic utilization efficiency, both schemes have their own characteristics. If the user has a high load during the day and a low load at night, AC coupling is better. The photovoltaic module directly supplies power to the load through a grid connected inverter, and the efficiency can reach over 96%. If the user has less load during the day and more at night, photovoltaic power generation needs to be stored during the day and reused at night. DC coupling is better. The photovoltaic module stores electricity to the battery through a controller, and the efficiency can reach over 95%. If it is AC coupling, photovoltaic power needs to be converted into AC power through an inverter first, and then into DC power through a bidirectional converter, and the efficiency will decrease to about 90%