China Electronics Academy's two companies' science and technology projects passed the acceptance

[ China Instrument Network Instrument R&D ] On July 19th, the State Grid Corporation undertook the "Flexible DC Power Distribution Control Strategy and Active Protection Mechanism Research" and "Multi-DC Feeding System Safety Quantitative Evaluation Technology Research" The science and technology project passed the acceptance inspection organized by the Ministry of Science and Technology.

With the wide access of distributed energy and DC loads, the development potential of DC distribution networks is huge, and the main factors restricting its development include the immaturity of control protection strategies. When the converter station fails, the DC protection action speed is very fast, and the main protection action time is usually less than 15ms. Therefore, the AC protection is only used as the backup protection for DC protection when the DC side is seriously faulty (such as phase-to-phase short circuit and DC-to-DC short circuit). The overcurrent protection of the 166kV connecting transformer should be considered as backup protection for the overcurrent protection of the DC protection valve or the differential protection of the starting circuit.

The energy equipment implementation plan of China Manufacturing 2025 has clearly pointed out the need to develop flexible DC distribution network converters, transformers, circuit breakers, and control protection systems for 10kV to 110kV distribution network systems.

The "Flexible DC Power Distribution Control Strategy and Active Protection Mechanism Research" project focuses on a typical application scenario of flexible DC power distribution, and designs a four-terminal ring-shaped, layered symmetric monopole bus structure with multiple elements, such as source, storage and load. The flexible DC distribution grid scheme proposes a three-layer operation control strategy based on the scheduling level-system level-device level and two fast primary protection methods based on single-ended voltage and current information and local high-frequency current components.

On the other hand, the operating characteristics of the AC grid with multiple DC feeds are complex. How to ensure the safety and stability of multi-DC feeding into the large grid will become a new challenge for power system operation and dispatch. The “Multi-DC Feeding System Safety Quantitative Evaluation Technology Research” project has studied the improved calculation method for evaluating the AC and DC and multi-DC mutual influence indicators, and proposed the AC and DC interaction static analysis method considering the external characteristics of various power system components. Considering multi-indicator and multi-feed DC falling point screening method based on node clustering clustering, the safety quantitative evaluation software for multi-DC feeding system for complex large power grid is developed.

The results of the “Flexible DC Power Distribution Control Strategy and Active Protection Mechanism Research” project supported the preparation of the “ITU Technical Requirements for DC Distribution Network and AC Distribution Network” and provided a strong support for the construction of DC distribution network. Technical support and scientific guidance. The results of the “Multi-DC Feeding System Safety Quantitative Evaluation Technology Research” project provide effective technical analysis methods and auxiliary decision-making basis for the quantitative assessment of grid safety after multi-DC feeding in large-scale power grid planning, and provide technology for improving grid planning efficiency. support. The breakthrough of the two achievements is conducive to China's continuous improvement of the development level of smart grid.

(Source: China Electric Power Research Institute, China Electrical Engineering Society, thesis world)