Energy storage is an important component and key technology for smart grid, renewable energy system and energy internet. With the explosion of large-scale energy storage market applications, 1MW energy storage system must be a standard application unit, and its research significance for grid-connected and off-grid applications of multi-microgrid is important.
Microgrid is a concept relative to the traditional large grid, which refers to a network composed of multiple distributed power sources and their associated loads according to a certain topology, and is an effective way to realize an active distribution grid and make the transition from a traditional grid to a smart grid.
Microgrid involves six major areas of power system: power generation, energy storage, distribution, electricity consumption, dispatching and communication, and it can work in both grid-connected and isolated modes with high reliability and stability.
2、Applications of Microgrid
The application market of microgrid is mainly divided into the following four areas:
1. Home microgrid: this market application is still relatively limited in China, and the microgrid with integrated light storage and charging is mostly used.
2. Industrial park microgrid: this application is more widely used.
3. Island microgrid: developing photovoltaic and wind power generation on the island to solve the stability and safety of electricity consumption on the island.
4. Remote/no electricity area microgrid: building micro multi-energy complementary The micro-grid can solve the problem of no electricity supply in remote areas.
The microgrid can be operated in parallel or in isolation, and the whole system is designed to be plug-and-play to improve the flexibility and reliability of power supply; the energy storage microgrid can also be used as a backup power source, using its black-start function; in addition, it can participate in the regulation of the main network through the local energy management system.
3、the type of micro network
1 Communication micro network
AC microgrid is mainly distributed energy through the coupling technology of AC bus, wind power, diesel power, photovoltaic and energy storage are connected to the system, and finally the whole system is connected to the big grid through the intelligent distribution cabinet, forming a simple AC microgrid.
This AC micro-grid application is very typical in current micro-grid energy storage applications or projects, and the technical aspects are relatively mature the application is very flexible. In all energy storage microgrid technology, it is relatively easy for equipment suppliers or system integrators to achieve system integration.
This type of AC microgrid is more suitable for island microgrid.
Because in the wider area of the island, energy can be supplemented by PV, together with the energy storage system, when the load is not consumed, the surplus power can be stored first and then powered to the load at night. When the whole system can’t generate electricity even in rainy days by PV, you can consider adding a diesel generator to use it as a backup power source.
Features of AC microgrid:
1. The system design of AC microgrid can support grid-connected operation and can also be operated off the grid.
2. The whole system has a large access power range and a more flexible design, which can access photovoltaic energy, wind power, super capacitor and other types of energy storage battery systems.
3. Support the application of ladder batteries, battery access to multiple branches, and reduce the parallel connection of battery groups.
4. The whole AC system microgrid can be made the container design scheme of PV, energy storage and battery integration. In smaller capacity occasions, energy storage batteries occupy a larger area, if the system device placed in a particular area without space, you can add a container in the outdoors, the overall package.
Key technologies of AC microgrid:
1. Microgrid energy management strategy, by managing the operating status of the load within the microgrid, is the economic and reliable operation of the microgrid. To form a micro-grid, it is necessary to do energy management scheduling and strategy control in the background.
2. seamless switching technology for parallel and off-grid to ensure the reliability of power supply for important loads within the micro-grid, which plays an important role in the safe and reliable operation of the large grid.
3. VSG function to increase system inertia and maintain the stability of the system voltage and frequency.
2 DC Microgrid
DC microgrid is mainly used in electric vehicle charging stations, industrial and commercial parks and some emergency power supply occasions. The system composition mainly considers two points:
1. Play the maximum role of PV. Because the PV and energy storage panels are indispensable in the microgrid, and energy storage is the core component of the whole microgrid equipment.
Photovoltaic power generation is generally DC power, the DC power generated by photovoltaic through the intermediate device into the DC bus, the battery through the intermediate DC converter into the system, so that photovoltaic power generation does not need to be inverted and then rectified back to the battery charging, the conversion efficiency of the whole system will be very high.
2.the current charging technology of electric vehicles mainly use AC charging pile or DC charging pile, the energy of this type of charging pile The energy of these charging piles is derived from AC power, and a DC micro-grid is built to convert the energy flow through DC charging DC to directly charge the electric vehicle, maximizing the conversion efficiency and utilization efficiency of the system.
The whole system is connected to the grid through the energy storage converter to play a complementary role, so that when the PV energy is insufficient or the load power supply, DC source and other similar loads need power supply, the power can be taken through the grid; when the electricity generated by the PV is not consumed, the surplus power can be put online.
DC microgrid features:
1. DC microgrid uses DC bus coupling technology to reduce AC-DC conversion losses.
2. make full use of photovoltaic power generation to achieve the power balance of the microgrid system.
3. maximize the reduction of grid-side distribution capacity, because many loads to be powered when taking power from the grid, the grid-side transformer configuration capacity will be very large, and if there are many DC loads, you can use DC microgrid this solution to solve.
4. as a simple emergency power supply, this emergency power supply can not do like the conventional UPS kind of seamless power supply switching, but the switching delay can be controlled within 15 milliseconds.
The key technologies of DC microgrid include
1. energy management system, which is a set of software for strategic control and scheduling of system energy.
2. impedance matching technology of DC converter, which can reduce the influence of filter circuit and output load change on the resonant frequency of the resonant circuit of the converter.
so that the resonant frequency of the resonant circuit of the converter only varies in a small frequency band, thus ensuring the high conversion efficiency of the converter and simplifying the control circuit of the converter.
3. The distributed cooperative control technology of segmented bus ensures the stability and adaptability of the cooperative system.
3 AC-DC hybrid microgrid
The AC-DC hybrid microgrid combines all the features of the previous two microgrid types and is very powerful, and the combination of the whole system has very high requirements on equipment and technology. In energy storage, PCS, etc.
1Mwh container energy storage technology solution and application
1、Solutions for Energy Storage Containers
1 Microgrid Energy Storage Solutions
Integrated battery, BMS, converter, intelligent switching cabinet, EMS and other core components are all placed inside a container, a 40-foot container can be done. This all-in-one solution can be used in the peak and frequency regulation of energy storage power plants, or the utilization of ladder batteries, emergency power supply and some commercial applications of peak shaving and valley filling.
2、Power Station Energy Storage Solutions
The scale of the whole system of energy storage power station is relatively large, I personally suggest separating the PCS and battery part and place them inside a container separately, which will be more reasonable in terms of maintenance and ventilation and heat dissipation of the battery.
3、Cabinet Energy Storage Solutions
This integrated energy storage solution is suitable for small commercial energy storage applications, and by placing the PCS and battery modules all inside one cabinet, the entire system takes up less space.https://anygap-energy.com/