What is energy storage? It is an important part of the six major links in the power production process, “collection-generating-transmission-distribution-use-storage”. The energy storage system can realize energy transfer and promote the application of new energy. It can establish a microgrid to provide electricity for areas without electricity. It can adjust peak frequency and frequency to improve the operation stability of the power system. The energy storage system has great strategic significance for the construction of smart grid.
The energy storage methods include: PCS energy storage, inductor-type energy storage, capacitor-type energy storage and other types of energy storage.
Ⅰ. What is a battery energy storage system?
Battery energy storage system (BESS) is a system that uses lithium batteries/lead batteries as energy storage carriers to store electrical energy and supply electrical energy for a certain period of time. Moreover, the electric energy provided has functions such as smooth transition, peak shaving and valley filling, frequency modulation and voltage regulation.
Inductor-type energy storage is an energy storage element, and the stored electrical energy is proportional to its own inductance and the square of the current flowing through it: E = L*I*I/2.
Since inductors have resistance at normal temperature, and the resistance consumes energy, many battery energy storage technologies use superconductors. Inductive energy storage is not yet mature, and its application is relatively small.
Capacitor-type energy storage is an energy storage element, and its stored electrical energy is proportional to its own capacitance and the square of the terminal voltage: E = C*U*U/2.
Capacitive energy storage is easy to maintain and does not require superconductors. Supercapacitors are produced by utilizing the characteristics of capacitor-type energy storage to provide instantaneous high power EV charging, and are suitable for applications such as lasers and flash lamps. In addition, there are other battery energy storage methods: such as mechanical energy storage.
Including energy storage, photovoltaics, hydropower, etc., the energy storage system is the core component of the microgrid, and is often used in conjunction with photovoltaics and wind power.
Because the battery energy storage has the advantages of relatively mature technology, large capacity, safety and reliability, low noise, strong environmental adaptability, and easy installation, energy storage systems often use batteries to store electrical energy.
At present, the hybrid energy storage system is mainly composed of energy storage unit and monitoring and dispatching management unit: the energy storage unit includes battery energy storage group (BA), battery management system (BMS), power conversion system(PCS), etc. Monitoring and dispatching management Units include central control system (MGCC), energy management system (EMS), etc.
At present, the more commonly used application modes are: energy-based energy storage systems, power-based energy storage systems, grid-level energy storage systems, commercial energy storage systems, and household energy storage systems.
Ⅱ. The composition technology of the battery energy storage system
The technology of the energy storage system mainly includes the management of the energy storage bidirectional inverter, the energy storage battery, and the reasonable scheduling of the system energy by the monitoring and dispatching management unit.
1. The battery management system
The battery management system (BMS) is installed in the energy storage battery pack and is responsible for the collection of voltage, temperature, current, capacity and other information, real-time status monitoring and fault analysis for the battery energy storage pack.
At the same time, it communicates with PCS, monitoring and dispatching system on-line through CAN bus to realize the optimal charge and discharge management control of the battery. Each cluster of battery packs in the system is equipped with a battery management system, which can achieve the purpose of effectively and efficiently using each cluster of energy storage batteries and the overall rational allocation.
2. The monitoring and scheduling management system
The monitoring and dispatching management system is the energy dispatching and management center of the battery energy storage unit, including the central control system (MGCC) and the energy management system (EMS).
It is responsible for collecting all battery management system data, energy storage converter data and power distribution cabinet data, issuing control commands to each part, controlling the operation of the entire energy storage system, and reasonably arranging the work of the energy storage converter.
The system can either run automatically according to the preset charging and discharging time, power and operating mode, or it can run under the immediate command of the operator.
Among them, the energy management system is the neural control system of the battery energy storage system. In order to realize the reasonable dispatch of energy, according to the peak-to-valley characteristics of the power grid, the economic operation of the micro-grid can be realized. control and other functions.