Energy Storage Converter
Energy storage converters (PCS), also known as "bi-directional energy storage inverters", are the core components of the two-way flow of electricity between the energy storage system and the grid, and are used to control the charging and discharging processes of the battery, and to perform the conversion of AC and DC currents. In the absence of grid, it can directly supply power to AC loads.
According to the application scenarios and capacity size of the energy storage converter, the energy storage converter can be divided into photovoltaic energy storage hybrid converter, small power energy storage converter, medium power energy storage converter, centralised energy storage converter and so on.
▶ Photovoltaic energy storage hybrid, low-power energy storage converters are used in household and industrial and commercial scenarios, where photovoltaic power generation can first be used by local loads, and the excess energy is stored in the batteries, which can be optionally connected to the grid if there is still a surplus of electrical energy.
▶ Medium-power, centralised storage converters can achieve higher output power and are used in industrial and commercial, power station and large-scale grid scenarios to achieve peak shaving, peak/frequency regulation and other functions.

Grid-connected inverters
Grid-tie inverters, dedicated to the field of solar photovoltaic power generation, play the biggest role in converting the DC power generated by solar cells into AC power that can be directly connected to the grid and loads through power electronic conversion technology.
Grid-connected inverter as the interface device between PV cells and the grid, converts the electrical energy of PV modules into AC electrical energy and transmits it to the grid, which plays a crucial role in the PV grid-connected power generation system. With the promotion of BIPV, in order to maximise the use of solar energy conversion efficiency, while taking into account the aesthetic appearance of the building, gradually diversified requirements for the inverter form. At present, the common solar inverter methods are: centralised inverter, string inverter, multi-string inverter and module inverter (micro inverter).

The "best partner":
Grid-connected inverters can only generate power during the day, and the power generated is affected by the weather, with unpredictability and other problems.
Energy storage converters can perfectly resolve these dilemmas. When the load is low, the output power is stored in batteries, and the stored power is released when the load peaks, reducing the pressure on the grid;
When the grid fails, the storage converter switches to off-grid mode to continue power supply.
The biggest difference: the demand for inverters in energy storage scenarios is more complex than in grid-connected PV scenarios. In addition to DC to AC conversion, it also needs to have the functions of converting from AC to DC, and fast switching between grid-connected and off-grid, etc. At the same time, the energy storage PCS is also a bi-directional converter, with energy control in both charging and discharging directions.
In other words, energy storage inverter has higher technical barriers.
Other differences are reflected in the following 3 points:
▶ Conventional PV inverters have a self-consumption rate of only 20%, while energy storage converters have a self-consumption rate of up to 80%;
▶ In the event of a utility power failure, the grid-connected inverter is paralysed, while the storage converter can still work efficiently;
▶ Against the background of decreasing subsidies for grid-connected power generation, storage converters are more profitable than PV inverters.


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