The press-pack IGBTs (PPIs) is a tightly coupled system of thermal, electrical and mechanical fields, of which the heat and borne pressure are transferred through inner layers while conducting current. Therefore, the aging mechanism of PPIs is different from that of power module IGBTs (PMIs). It is necessary to adopt new test methods to carry out accelerated aging test, as to obtain more analysis data for the research of aging mechanism.In this paper, according to existing references, an accelerated aging testing method with multi-excitation sources and multi-parameter monitors is implemented on the PPIs based on the half-bridge MMC sub-module to figure out the failure process. Combined with characteristics of the chip and package, methods with multi-excitation sources including high junction temperature operating test, impulse cycling test, power cycling test and temperature cycling test are studied, with the test topology and parameter setting principle defined, so as to comprehensively stimulate the aging failure process of PPIs. In order to observe the degradation process of PPIs as far as possible, an on-line monitoring method and a periodic discrete monitoring method are proposed to monitor the characteristic parameters of PPIs, such as the collector current, forward saturation voltage drop and the case temperature of the heat sink.

The voltage stability characteristics of the AC/DC receiving-end grid are closely related to the control strategy and operating status of the DC system. This paper proposes a static voltage stability calculation method considering the transition operation mode of the DC system. Through the mechanism analysis of the voltage response characteristics, the switching strategy of the converter control mode is constructed. The introduction of the DC power participation factor into the continuous power flow equation characterizes the participation of the DC system in the transition mode, which effectively solves the static voltage stability analysis in the scenario where DC power participates in the incremental load balance. An example of static voltage stability analysis of a receiving-end regional power grid of CSG verifies the effectiveness of the proposed method, and an in-depth comparison and analysis of the converters’ operation control strategy and HVDC power participation factors are conducted. The research results have reference value for the operation and control of AC/DC receiving-end power grids.

The rapid development in the fields of wireless networks, the Internet of Things, and artificial intelligence obviously promote the progress of intelligent building management system function. Then, the related reasonable application for all sorts of advanced technologies and its coordination control for new DC devices in the intelligent building become urgent problems to be solved. Firstly, in this paper, the development of the intelligent building management system in different stages is summarized, and combined with the development and application of various new technology fields, the development direction of new intelligent building management is studied. Next, Considering the integration of these new DC controllable equipment, the control architecture of the DC building distribution system, and the problems faced by the application of energy management system in the intelligent building are analyzed. Finally, based on the above, this paper puts forward the suitable integration mode of the energy management system and building management system in DC building distribution system to meet the interaction requirements of different operation and management modes, to realize the coordinated control and optimization for energy saving among different equipment.

As the protection equipment of the DC distribution network, the DC circuit breaker is of great significance to the safe and stable operation of the DC distribution network. A topology design scheme for cascaded modular solid-state DC circuit breakers suitable for DC distribution networks is proposed. The topology of the proposed scheme reduces the pressure on the arrester to absorb energy and accelerates the current breaking speed by introducing a grounding diversion diode group; the transfer branch adopts a cascaded modular structure to solve the problem of dynamic voltage equalization of a large number of IGBTs connected in series. The DC circuit breaker model of 10 kV DC distribution network is designed based on the proposed topology, which is verified in PSCAD/EMTDC, and analyzed and compared with other literatures. The results indicate that the maximum breaking current of the solid-state DC circuit breaker based on the proposed scheme is 5 kA, the fastest time to remove the fault current is 2.96 ms, and the time for the arrester to absorb energy is 1.24 ms. The energy absorbed is halved compared with other schemes, which is in consistent with DC circuit breaker design requirements. The feasibility of the scheme is verified by the simulation results in this paper.

Submarine cable plays an important role in marine energy development, island economic development and national territorial security, etc. It is a necessary method to ensure the safe and reliable operation of submarine cable system by carrying out regular detection of its routing, embedding depth, fault and other information. In this paper, five kinds of detection methods are briefly expounded, include the artificial outlook, patrol, ocean "fish" and so on, and their advantages and disadvantages are analyzed. Then from the angle of detection technology, the submarine cable detection technology based on the optical, electrical, acoustic, magnetism, and information fusion principle are introduced in detail, and each detection technology’s advantages and limitations are discussed based on its development and application status at home and abroad. At last, the problems and the development trend of the submarine cable detection technology is pointed out in this paper.

This paper aimes at the automatic target detection of ground penetrating radar in goaf area of the power transmission corridor complex underground environment. A generalized likelihood ratio test (GLRT) of target’s hyperbolic characteristic is proposed. In this method, the spherically invariant random process is used to describe the non-Gaussian clutter background. The hyperbola is tested as a whole to be decided whether it is originated from a target or not. So the target characteristic and the statistical properties are fully utilized to enhance the signal to clutter/noise ratio gain. Furthermore, an approximated GLRT is derived to simplify computation under the premise in detection performance. The approximated GLRT is insensitive to the distribution type of clutter, and in consequences, is of great engineering value. Experiments and the results analysis verify the performance of the proposed methods.

Leakage fault is one of the popular problems of cable terminals hindering the safe operation of cables, and there is no clear detection means at present. This paper proposes a detection method of terminal leakage fault based on infrared thermography. Firstly, the numerical simulation model of oil leakage is built, the formation mechanism of surface temperature difference caused by oil leakage in terms of the basic principles of heat transfer is analyzed. Then, the above mechanism is simulated and verified through finite element method. Simulation results show that the temperature difference of terminal surface corresponding to air layer and silicone oil layer increases gradually with the decrease of liquid level. Finally, by comparing the infrared detection with terminal disassembly, the feasibility of applying infrared thermography to the leakage detection of cable terminal is verified.

At present, the communication between dispatching and substation is mainly protected by the power vertical encryption authentication device. The power vertical encryption authentication device at both ends of the dispatching and substation can protect the confidentiality and integrity of data transmission at both ends. However, the communication protocol IEC 60870-5-104 (IEC104) between dispatching and substation does not have a corresponding security mechanism. The protocol data is easy to be forged, tampered, replayed and stolen before the encryption device of the dispatch and after the encryption device of the substation, which poses certain security risks. Therefore, this paper extends the protocol security domain on the basis of IEC 104 protocol, and solves the problem of communication security between dispatch and substation from the protocol level. The identity-based cryptographic algorithm SM9 provides algorithmic support to achieve this goal. According to the characteristics of the algorithm and the protocol, the security of the protocol can be realized by a little extension of the protocol in this paper. The highlights of this paper are as followes: 1) based on the identity-based cryptographic algorithm the security communication between dispatching and substation is achieved, which is fundamentally different from the digital certificate based security communication in other documents, without certificate management and other complicated matters; 2) the end-to-end security authentication of the communication between the dispatching master station and the substation is achieved; 3) the security hidden dangers of the protocol are solved through the identity-based cryptographic algorithm, and the two-way identity authentication between the dispatching and the substation and the confidentiality, integrity and non-repudiation of the communication data are realized.

The low-voltage distribution automation terminal is an important part of the distribution network, which has the characteristics of multi-faceted and wide-ranging. With the great investment of CSG (China Southern Power Grid Company Limited) in distribution automation, the installation, debugging, operation and maintenance of the massive access of low-voltage distribution automation terminals difficult problems are particularly prominent. Therefore, this paper proposes a plug and play implementation method for station equipment based on IEC 61850. Firstly, a model design method based on the IEC 61850 standard is proposed to realize standardized access and communication point table configuration of end devices. Secondly, based on the model design method, a plug and play system and control of APP loading, unloading, and dynamic tracking of multiple instances are designed. The method realizes the standardization and uniformity of equipment communication, and ensures the safety, integrity and reliability of the replacement and access work of terminal equipment. Finally, the method proposed in this paper is applied to China Southern Power Grid to verify the advancement and feasibility of the method. The application results show that the method has a very positive guiding significance and reference value for practical problems such as complex on-site construction processes and cumbersome personnel operations.

In the open electricity market, the introduction of a price-based demand response can make market competition more efficient and electricity prices more reasonable. However, the time-of-use price can not reflect the actual market supply and demand. The real-time price is highly volatile and difficult to implement. In order to combine the demand-side response with the electricity market, this paper proposes the variable peak price products and analyzes its characteristics and benefits in combination with the development of electricity market of China. On this basis, based on the user’s electricity price response model, the operational optimization model of both purchase and sale considering customer satisfaction is established, and three scenarios are designed for case analysis. The results show that the variable peak price product can increase the total revenue of balance account, increase the profit of the retailer and users, and reduce the load peak-to-valley difference under the premise of ensuring the cost of the user’s electricity unchanged.

With the wide area measurement system (WAMS) being widely used in power system, extensive online measured data can be obtained for power system analysis and calculation. In this paper, online parameter identification method of doubly fed induction generator (DFIG) is studied using WAMS data. Firstly, a simplified DFIG model for identification is established, and it is proved that online parameter identification of power system based on WAMS is a closed-loop identification, and this problem can be solved by using prediction error method (PEM). Then, the paper proposes two PEM implementations: Kalman filter method and data transformation method, and compares the similarities and differences between them. Finally, the effectiveness and feasibility of the two methods are validated by using WAMS data obtained from wind farm data in Ningxia Power Grid.

For digital power grid, this paper discusses the main application scenarios of edge computing and Internet of Things technology, proposes a data processing model of edge computing based on container technology designs and a cloud-edge-collaborative edge data processing architecture, and realizes edge computing embedded database based on container technology and the key technology of cloud-edge data synchronization. A data filtering mechanism is researched, and according to the priority of transaction operation, the transaction is screened and reconstructed. The performance test of embedded database based on container technology and data synchronization experiment of cloud-edge collaboration are completed. The experimental results show that the write, query and export performance of edge computing database technology based on container technology is almost the same as that of embedded database. The efficiency of full-volume data synchronization realized by cloud-edge data synchronization tool is three times than that with the traditional method. The incremental data synchronization method improves the timeliness of synchronization and effectively saves the time cost of full-volume synchronization each time.

Regional multi-energy systems is an effective way to solve the multi-energy complementary energy utilization, which can be used in ways such as multi-energy complementarity and step-by-step energy utilization to maximize energy utilization efficiency and absorption of renewable energy. And with the development of cloud computing, big data, Internet of Things, artificial intelligence and other technologies, the future energy system is not only the interconnection of energy, but also the coupling of energy and information. This paper analyzes the current research status of regional multi-energy systems,the problems of regional multi-energy systems in planning,operation and simulation modeling are summarized. This paper introduces the digital twinning technology into the regional multi-energy systems research, and analyzes the application of digital twinning technology from the aspects of regional multi-energy systems simulation modeling, planning operation and maintenance. It provives the refererenc for the future research on the digital twinning of regional multi-energy systems.

Live operation of 10 kV lines is carried out in distribution network, in which J-type wire clamp are widely applied to live-line connection/disconnetion operation. It is of great significance to study the working status of J-type wire clamp. Using the 3-D multi-physics coupling method, an equal proportion model and a 3-D mechanical-electrical-thermal coupled model are established to analyze the stress distribution, current density distribution and temperature distribution of 10 kV J-type wire clamp. The result shows that the stress distribution, current transmission and temperature distribution are extremely uneven. The maximum stress of contact surface reaches 6.8×10⁹ N/m², and the maximum displacement of the wire clamp is 1.04 mm. The current between the wire clamp and the wire is concentrated in the 1/4 area of the contact surface, where more than 60% of the current flows, resulting in the utilization ratio of the contact surface is low, but the current density distribution between the wire clamp is relatively uniform. The highest temperature occurs in the groove of the wire, with a value of 50 K.

The extreme disasters have brought severe shock to the safe operation of power system, and caused great damage to distribution power network equipment and large-scale outage. In order to accelerate the process of post-disaster recovery, quick repairing to the damaged equipment is required. However, owing to the uncertainty of the fault location and lack of interaction in repairing dispatching scheme, there exists the problems of mispairing and idleness of repairing crew, leading to the low efficiency of fault repairing and post-disaster recovery. This paper focuses on this problem and proposes a dynamic post-disaster repairing strategy based on rolling optimization. Considering complex fault scenarios, the outage nodes near normal-operating upstream nodes will be first repaired. The single-phase optimization model has been formulated to solve dispatching problem between repairing crews and certain fault points, in order to lower the weighted load loss. Furthermore, considering the repairing completion, power recovery and fault point detection, a rolling optimization decision process has been designed and repairing crews can be dispatched dynamically. The cases validate that the strategy proposed in this paper can effectively promote the efficiency of repairing, avoid the phenomena of mispairing and idleness of repairing crews and accelerate the process of post-disaster recovery.

The stray current generated by the subway could cause DC magnetic bias in the transformers of the urban power system, threatening the safe and stable operation of the transformer and the power system. In order to solve this problem, a platform monitoring the stray current invading the substation and the DC magnetic bias characteristic of the transformer is developed. According to the monitoring result, the characteristics of the amplitude, distribution and flow direction of the intrusive stray current are analyzed, and the influence of the time period, the subway operation mode, the substation location and the number of nearby subway lines on the DC bias characteristic of the transformer are studied. The results show that the stray current through the neutral point of the transformer could cause severe DC magnetic bias problem, and there might be a metallic transmission path for the stray current between the subway system and the power system. Thus, it is necessary to carry out targeted research on relevant prevention measures from the source in conjunction with the planning and site selection of the substation.