China has made a breakthrough in the field of energy storage, as it developed the world’s first hundred-megawatt high-voltage cascaded direct-mounted energy storage system. The system was announced by the National Energy Administration as one of the first major technical equipment (and equipment sets) in the energy field.
The system is a joint project of Tsinghua University, China Three Gorges Corporation, China Power International Development Co., Ltd., and Xi’an Xidian Electric Power System Co., Ltd. It is based on the research of a team of academics from the Department of Electrical Engineering of Tsinghua University, the DC Research Center of Tsinghua University Energy Internet Research Institute, and the DC Research Institute of the Tsinghua Sichuan Energy Internet Research Institute.
The system is a remarkable achievement in the field of energy storage, as it overcomes the problems of existing large-capacity energy storage systems that adopt distributed parallel solutions. These solutions are prone to harmonic oscillation, low power conversion efficiency, and high requirements for battery management systems. The system adopts a novel design of high-voltage cascaded direct-mounted energy storage, which integrates the battery, converter, and system levels into a coordinated and balanced control technology system. This design improves the stability, efficiency, and reliability of the system, and reduces the complexity and cost of the system.
Figure: Hundred-megawatt-level high-voltage cascaded direct-mounted energy storage system topology
功率单元: power unit
电池组: battery pack
直流滤波支路: DC filter branch
H桥逆变电路: H-bridge inverter circuit
电池单元: battery cell
换流链: converter chain
交流电网: AC grid
H桥功率单元: H-bridge power unit
电池储能单元: battery energy storage unit
单元1/单元2/单元N: unit 1/unit 2/unit N
b相簇/c相簇: b-phase group/c-phase group
国产IGCT: domestic IGCT
The system has the largest single machine capacity in the world, as it can store and output 100MW of active power and 140MVar of reactive power. It also has a fast response time, as it can respond to grid dispatching instructions within a few milliseconds, and adjust active and reactive power from 0 to 100% within tens of milliseconds. Moreover, it can perform both energy storage and reactive power compensation functions, and provide inertia support for new energy power systems. This means that it can operate in four quadrants, and enhance the stability and flexibility of the grid. Furthermore, it is based on domestic devices, as it uses IGCT-Plus devices independently produced by China. This reduces the dependence on foreign technology, and increases the self-reliance of China’s energy sector.
The system can effectively solve the stability issues behind large-scale new energy power stations, and facilitate complementarity of wind and solar energy storage at multiple time scales. It is an important technical means to improve large-scale new energy consumption and solve the problem of insufficient active support capabilities.
Figure: Power conversion cabin of high-voltage cascade direct-mounted energy storage system
The project team is currently developing a 50MW/100MWh high-voltage cascaded direct-mounted energy storage system and a 100MW/200MWh high-voltage cascaded direct-mounted energy storage system. Upon completion, they will become the largest direct-mounted energy storage systems in the world.
In addition, with the implementation of the carbon peaking and carbon neutrality goals and the continuous advancement of new power system construction, the “hundred-megawatt-level high-voltage cascaded direct-mounted energy storage system” will have vital potential to be applied in scenarios such as large-scale new energy development. The project has formed a “replicable and scalable” large-scale energy storage development plan, which is essential to building a new power system and improving the grid's capability to take in renewable energy.
