"The spring breeze brings hundreds and thousands of flowers". In these days when the warm spring comes and the pandemic is effectively controlled, the streets in Lize Financial Business District between the West Second Ring Road and the Third Ring Road in Beijing are already full of flowers on both sides. As the energy core of the Lize Business District, Dongguantou Substation of Fengtai Power Supply Bureau carried out a major upgrade in the energy Internet "information energy equipment", the digital lossless echelon utilization and energy storage system of decommissioned power batteries developed by the information energy team led by researcher Ci Song of EEA, Tsinghua University was installed, deployed and incorporated into the grid in full power at Dongguantou Substation of Fengtai Power Supply Bureau. The system design capacity is 400kW/800kWh, including subsystems for AC-DC converters, DC charging piles, decommissioned power battery energy storage and distributed photovoltaic power generation.

As the energy core of multi-station integration, the energy storage system of this project adopts the digital lossless echelon energy storage system for decommissioned power batteries proposed by the Department of Electrical Engineering of Applied Electronics of Tsinghua University to complete the seamless connection of battery modules directly from electric vehicles to energy storage stations without rigid disassembling, sorting and reorganizing the decommissioned power batteries at the monomer level, provide a new model and new method for the high-safety, high-efficiency and low-cost reuse of decommissioned power batteries, and created significant economic and social benefits. In this project, the digital energy storage system has realized the mixed use of batteries of different types, batches and capacities and online detection and automatic isolation of faulty batteries through millisecond-level battery topology reconstruction, and the tolerance for inconsistency of battery modules reaches 100%. It has fundamentally solved the industrial pain point of battery short-board effect, and greatly improved the economical efficiency, reliability and safety of battery energy storage systems. Therefore, this technology is adopted by the International Telecommunications Union (ITU) in the 5G sustainable power supply standard and granted a gold award in the 2021 International Exhibition of Inventions of Geneva. Up to now, digital energy storage systems have been applied to power grids, operators, power generation companies, electric vehicles, batteries, and solid waste environmental protection industries, and achieved favourable economic and social benefits. The cumulative capacity of digital energy storage systems in planning and in construction has exceeded 60MW/130MWh.

In recent years, Tsinghua University and the State Grid Corporation of China have deepened their cooperation and established a "New Generation Power System" joint research institute, and this project is a application of the research achievement of "Information energy integrating technology and equipment R&D" of a project established by the joint research institute in 2020. Moreover, the Department of Electrical Engineering and Applied Electronics of Tsinghua University and Beijing Electric Power Company discussed a new cooperation model. In 2019-2020, the two sides realized mutual visits, exchanges and a cooperative research mechanisms, and established a project "Digital energy storage system control architecture and reliable operation assessment supporting energy information integration”. The installation, deployment and successful incorporation into the grid at the Dongguantou Substation of Fengtai Power Supply Bureau is a model achievement of comprehensive cooperation between a university and enterprises.