Classification of Energy Storage PCS

As the global energy structure transforms and renewable energy rapidly develops, energy storage systems play a more and more significant role in the stable operation of power grids and energy management. As the core component of energy storage systems, the Power Conversion System (PCS) undertakes the important mission of electric energy conversion and control.

Below is the classification and characteristics of energy storage PCS.

The role of the energy storage PCS in the energy storage system is: first, when charging, it can cleverly convert the AC power of the power grid into DC power to charge the energy storage battery and store the electrical energy; second, when discharging, it can accurately invert the DC power output by the battery into AC power and transmit it back to the power grid or directly supply it to electrical equipment for use, ensuring a stable supply of electricity.

Classification by Application Scenarios：

(1) Residential Energy Storage PCS

Household energy storage systems are mainly used in home scenarios. The power of household energy storage PCS is relatively small, generally around 5-10kW. It is characterized by its small size and easy installation, and can perfectly cooperate with distributed energy systems such as household solar panels. It can store solar power during the day and supply it to households at night. It can not only save electricity bills, but also serve as a backup power source when the power grid is out, ensuring the basic electricity needs of the household and creating a stable and reliable microgrid environment for the family.

(2) Industrial and Commercial Energy Storage PCS

Industrial and commercial energy storage systems serve industrial enterprises and commercial places. The power of this type of PCS is usually between 50kW and 500kW. It needs to face more complex power demand and working conditions, and has higher conversion efficiency and stronger stability. It can help enterprises to reduce peak loads and fill valleys, that is, store electricity during low power consumption and release electricity during peak power consumption, thereby reducing the electricity cost of enterprises. At the same time, it can also improve the reliability of enterprise electricity consumption and avoid the impact of power grid fluctuations or power outages on production and operation. It is a powerful assistant for enterprise energy management.

(3) Large-scale Energy Storage Power Station PCS

Large-scale energy storage power stations undertake multiple important functions in the power system, such as frequency regulation, voltage regulation, and standby. Their PCS power is often at the megawatt level or even higher, ranging from several megawatts to hundreds of megawatts. Large-scale energy storage power station PCS has extremely high requirements for the system's response speed and control accuracy. It needs to have strong grid connection capabilities and multi-machine parallel operation capabilities to ensure the safe, stable and efficient operation of the power system during large-scale power conversion. It is an indispensable and important part of the construction of modern smart grids.

Classification by Technical Route

(1) String PCS

The string power conversion system (PCS) supports multi-branch battery access and cluster management and independent control, which significantly improves battery utilization, is easy to operate and maintain, and is easy to expand. Although the cost is high, the long-term benefits are obvious. At the same time, the system effectively solves the problem of parallel circulation of battery clusters. When a single PCS cabinet fails, the impact range is small and it is easy to operate and maintain, ensuring the high reliability and maintainability of the energy storage system.

(2) Centralized PCS

Centralized PCS is widely popular in the energy storage field due to its mature technology, low cost, simple structure and convenient regulation. However, the challenge is that the voltage tolerance of its switching devices limits the expansion of the system, and a step-up transformer is often required for grid connection; the battery pack is difficult to finely balance, which affects system performance; and the entire machine is shut down in the event of a fault, resulting in high operation and maintenance costs, which affects the online rate and utilization rate, and increases the burden of later operation and maintenance.

(3) Distributed PCS

Distributed PCS is a power conversion system that uses a two-level AC/DC+DC/DC topology. It solves the problem of parallel circulation of battery clusters by adding DC/DC isolation before each battery cluster is connected to the DC bus in parallel, thereby improving battery utilization and system efficiency. At the same time, distributed PCS has high flexibility and scalability, and is easy to operate and manage. However, due to the addition of DC/DC isolation, its power conversion loss may increase, and the system structure is relatively complex, with high requirements for safety and stability.

As an important part of new energy, energy storage technology is gradually changing the way we use energy. As the core brain of the energy storage system, the power conversion system (PCS) plays a pivotal role. Different types of PCS systems have different characteristics. The selection of PCS is a complex and meticulous process that requires comprehensive review and careful consideration. Only by closely combining the actual needs and technical conditions of the project can we ensure that the selected solution is the most suitable and appropriate. This will lay a solid foundation for the efficient and stable operation of the energy storage system and promote the continuous development and application of energy storage technology.