The energy storage system can be connected to the power grid as an independent system, and can play the role of peak shaving and valley filling, reactive power compensation, etc.;
The energy storage system can also be built in the load center together with new energy power generation systems such as wind power generation and photovoltaic power generation to form a micro-grid system to improve energy utilization efficiency, improve power quality, improve power supply reliability, and reflect green environmental protection.
According to the new energy access mode, the energy storage system in microgrid can be divided into two control modes: common DC bus and common AC bus. The micro-grid power supply is realized through the multi-direction converter system to ensure that the electricity load can run uninterrupted even in the state of grid blackout.
1. Pure energy storage system solutions
When discharging, the electric energy is converted into alternating current that meets the grid through the bidirectional converter, and the electric energy is fed back to the grid. When charging, the AC power of the grid is rectified into DC power through the bidirectional converter to charge the energy storage battery. Both the DC side and the AC side can be connected to and powered by loads of corresponding types and power levels.
The scheme has multiple uses: the energy storage system can shave peaks and fill valleys in the power grid, operate independently with load after the power grid is powered off, and can perform reactive power compensation for the power grid to improve the power quality of the power grid and reduce line losses.
The biggest advantage of this scheme is that the control strategy is simple, the equipment has high versatility, and the application range is wide.
2. Common DC bus microgrid energy storage system solution
New energy power generation equipment and energy storage batteries are connected to the DC bus side of the multidirectional converter. The multidirectional converter system consists of a bidirectional converter and an inverter. The bidirectional converter is a bidirectional converter device for energy exchange between the DC bus and the public grid, and the inverter is a microgrid bus. The load provides a bidirectional DC-AC converter.
The energy generated by new energy can be charged in the form of DC for battery energy storage, or it can be converted back to the city grid by bidirectional converter, and it can also provide AC power for the microgrid load through the inverter.
In the case of mains power failure, the bidirectional converter stops running, and the new energy power generation system, energy storage system and micro-grid side inverter can continue to work, ensuring uninterrupted power supply to the micro-grid load and truly realizing seamless switching.
The biggest advantage of this scheme is that the control logic is simple, the automatic control mode of each subsystem of the battery energy storage is relatively independent, the quality of the AC output power of the microgrid is good, and the overall system reliability is high.
3. Common AC busbar microgrid energy storage system solution
In this wiring scheme, the new energy power generation equipment is connected to the AC side of the microgrid of the multidirectional converter. The multidirectional converter is composed of two bidirectional converters, and is an energy exchange device between the public power grid, the energy storage battery, and the AC microgrid.
The new energy power generation can be directly supplied to the microgrid load in the form of alternating current through the converter equipment, and when the power generation is sufficient, the multi-directional converter can also be used to charge the battery for energy storage or feed back the power to the city grid.
In the case of mains power failure, the grid-side bidirectional converter stops running, and the new energy system power generation, energy storage system and the microgrid side bidirectional converter can continue to work, ensuring uninterrupted power supply to the microgrid load and realizing seamless switching.
At this time, the new energy generation energy is sufficient, in addition to supplying power to the load on the microgrid side, it can also charge the battery energy storage. The biggest advantage of this scheme is that the new energy power generation system is relatively independent, the equipment has high versatility and a wide range of options.