Energy storage systems can be connected to the power grid as independent systems and play roles in peak shaving, valley filling, and reactive power compensation. Energy storage system can also be combined with renewable energy generation to form wind and solar energy storage systems, which can smooth out the power output of the renewable energy generation side when it is connected to the grid.
Energy storage systems can also be installed in the load center with other renewable energy generation systems, such as wind and photovoltaic generation, to form microgrid systems, which can improve energy utilization efficiency, enhance power quality, increase power supply reliability, and promote environmental protection.
According to the mode of renewable energy access, the energy storage microgrid system can be divided into two control modes: common DC bus and common AC bus. The system can provide power supply through a multi-directional inverter system, ensuring uninterrupted operation of the power load even in the event of a main grid power outage.
During discharge, the electric energy is converted into AC power that meets the requirements of the grid through a bidirectional converter and fed back to the grid. During charging, the AC power from the grid is rectified into DC power and stored in the energy storage battery through a bidirectional converter.
Both DC and AC loads of corresponding types and power levels can be connected on both the DC and AC sides and powered accordingly.
This solution can be used for peak-shaving and valley-filling of the grid, independent island operation and stand-alone operation after power failure, and reactive power compensation to improve the quality of the grid and reduce line loss.
The biggest advantage of this solution is its simple control strategy, high device versatility, and wide range of applications.
New energy generation equipment and energy storage batteries are connected to the DC bus side of the multi-directional converter. The multi-directional converter system consists of a bidirectional converter and an inverter, where the bidirectional converter is a bidirectional power exchange device between the DC bus and the public grid, and the inverter provides stable AC power for the microgrid load.
New energy generated can be stored in the battery energy storage as DC power, converted back to the grid through the bidirectional converter, or provided to the microgrid load as AC power through the inverter.
In the event of a power outage, the bidirectional converter stops running, but the new energy generation system, energy storage system, and microgrid-side inverter can still operate to ensure uninterrupted power supply to the microgrid load and achieve seamless switching.
The biggest advantage of this solution is its simple control logic, relatively independent automatic control of battery energy storage subsystems, good quality AC output power of the microgrid, and high overall system reliability.
In this wiring scheme, the renewable energy generation equipment is connected to the AC-side of the multifunctional converter in the microgrid. The converter, consisting of 2 bidirectional inverters, serves as the energy exchange device among the utility grid, energy storage batteries, and AC microgrid.
The renewable energy generation can be directly supplied to the microgrid load in the form of AC through the converter. When the generation is sufficient, the surplus can also be used to charge the battery energy storage or fed back to the grid through the converter.
In case of power outage from the utility grid, the bidirectional inverter on the grid side stops operating, but the renewable energy system and energy storage system along with the other bidirectional inverter on the microgrid side can still operate, ensuring uninterrupted power supply to the microgrid load with seamless switching.
In this scenario, when the renewable energy generation is abundant, it can not only supply power to the microgrid load but also be used to charge the battery energy storage. The major advantage of this solution is the relative independence of the renewable energy generation system, high compatibility of equipment, and broad range of options for selection.