With the rapid advancement of the transformation of China's energy structure, energy storage, as a high-quality flexible adjustment resource and active support means, has become a strong support for the new power system to address the challenges of grid security.
The EMS system should adopt an open, layered, distributed system structure. When any part of the system fails, the overall system and other parts within the system can continue to operate normally. The system should be highly reliable and redundant, with the station control layer host using a dual-host redundancy structure, the station control layer network employing a redundant network, and the interval layer measurement and control devices and protection devices utilizing dual networks, dual CPUs, dual power supplies, and dual mainframe hot backup redundancy configurations to ensure that local faults in the system do not affect the normal operation of on-site equipment.
On December 1, 2023, the national standard "Technical Specification for Monitoring Systems of Electrochemical Energy Storage Power Stations" (GB/T42726-2023) was officially implemented. The national standard specifies the requirements for data collection, storage processing, control and adjustment, alarm, event sequence recording and incident recall, communication, etc., for monitoring systems of electrochemical energy storage power stations. Combined with industry development trends, the main functions of the EMS are as follows.
First, the data information volume of electrochemical energy storage power stations is enormous, with data volumes exceeding 600,000 for hundred-megawatt-level electrochemical energy storage power stations, especially as the signals for voltage, temperature, current, etc., in the energy storage system are exceptionally large. This data information needs to be sent to the EMS, which achieves remote monitoring through the collection of massive data from devices such as BMS and PCS after data processing. At the same time, the EMS data storage device must store massive amounts of data for later statistical analysis, with the national standard stipulating that the data storage capacity must be no less than 3 months.
Second, with the construction of the electricity market, medium and large electrochemical energy storage power stations can participate in ancillary service markets or electricity spot markets, providing multiple services such as peak shaving, frequency regulation, emergency power support, and smoothing power output to the grid. The EMS needs to have the capability to receive dispatch AGC, AVC, and other dispatch control functions, as well as the ability to coordinate and interact with new energy sources such as wind and solar power.
Finally, the EMS must have fast and reliable communication capabilities with on-site devices such as PCS and BMS. Generally, medium and large energy storage power stations adopt dual-host dual-network redundancy configurations, and communication protocols typically use protocols such as 104 and 61850. The national standard stipulates that the response time for the EMS to issue control commands to on-site devices should not exceed 1 second.
For large-scale energy storage power stations, the entire station is usually composed of several energy storage substations, each containing a certain number of battery packs, corresponding BMS, and PCS, etc. Different networking methods for energy storage systems are not entirely the same, but they typically have the following characteristics:
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To enhance the reliability and stability of the system, redundant networking (i.e., AB network) is usually adopted. For critical devices/servers, a master-backup configuration is also required. When the system network is functioning normally, data and signaling are transmitted through the A network; if the A network fails, it switches to the B network for transmission. If the main device/server fails, the backup device/server will take over the main device.
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The master station is equipped with a time synchronization device, data server, application server, and operator and engineer workstations, etc. For large-scale energy storage power stations, front-end servers, coordinating controllers, and other devices are also configured.
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Substations are usually equipped with protection measurement and control devices and other equipment for monitoring and protecting substation equipment and working environments.
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The energy storage master station is equipped with a remote control device for communication with the grid dispatch. On one hand, it uploads key equipment and status information of the energy storage station to the dispatch center; on the other hand, it receives instructions from the grid dispatch and participates in ancillary services for the grid.