Power cycle test is a kind of life analysis experiment based on accelerated aging and also a kind of reliability study method. It plays a key role in the reliability study of large-capacity power electronics. In this paper a power cycle simulation study of a press-pack IGBT module based on semi-direct electrothermal coupling is presented, and electrothermal coupling steady state and transient state models are established, and the equivalent conductivity based on the power loss of the chip is derived. And the load setting is carried out by the method of equivalent conductivity, and the internal temperature distribution of the press-pack IGBT module during power cycling and the change with time are obtained. This method can effectively reduce the huge computational load caused by transient direct coupling and avoid the problem of iterative non-convergence, and it has a certaintheoretical guidance for power module reliability research and life prediction.

Recently multi-terminal HVDC system (MTDC) has become a competitive alternative for inter-area large power transmission. The Kunbei-Liuzhou-Longmen (KLL) MTDC project promotes MTDC practice to ultra-high voltage level. It is composed of one LCC (Kunbei) and two VSC (Liuzhou, Longmen) converter stations in parallel, the operation mode of the system is flexible. And in the process of fault clearing and recovery, control coordination among three converter stations is needed. Thus, the conventional control and protection system for bi-terminal HVDC and the associated special protection scheme (SPS) cannot be directly adopted in KLL multi-terminal HVDC. This paper first introduces the MTDC line fault recovery (DCFR) and converter station online disconnection (CSOD) of KLL MTDC that used in system analysis, and the frequency response characteristic of the sending end AC system when it suffers a significant power imbalance. Then, the impacts of DCFR and CSOD and the corresponding SPS are studied and verified by transient stability simulation using real operational planning data. The study provides a reference for the SPS design of KLL MTDC and other MTDCs.

Integrated design technology of external cooling system of voltage source converter (VSC) valve and water-cooled transformer is suitable for the design of key equipment external cooling systems such as converter valve and water-cooled transformer. This paper proposes a optimal design scheme for VSC valve and transformer external cooling system, which shares one water spray pool and one spray water treatment system, and also gives spray water yield analysis and calculation based on one stage and two stage of first level reverse osmosis system. This scheme can save water and reduce pollution, and is convenient for the converter station maintenance and management. It can be widely used in the equipment cooling system design of HVDC converter station on land and offshore wind power HVDC station.

With the increase of power load in power grid, the problem of voltage stability in DC receiving-end becomes more and more serious because of the lack of reactive power. In the past literature, this problem has been solved mainly on the system structure design level, more inclined to the pre-prevention aspect, and little attention has been paid to the post control, especially the implementation of measures. Stability control device is the final outlet of control measures, and the rationality of setting value determines the effectiveness of control command. At present, the related research is not systematic enough, and the theoretical basis of actual setting is relatively weak. This paper studies the control strategy and the optimization of setting value for stability control device, puts forward the corresponding setting direction and target for different scenarios, and then gives the overall process of setting value optimization, which can provide theoretical support for the setting work. Finally, the effectiveness and practicability of the proposed method are verified by a China Southern Power Grid practical example.

DC circuit breaker is the key equipment to construct DC power grid, transmission line and converter station can be connnected to DC power grid by closing DC circuit breaker, and the temporary fault of the transmission line can also be recovered by the reclosing operation of DC circuit breaker. In this paper, the hybrid DC circuit breaker is taken as the research object. Firstly, the closing/reclosing principles of hybrid DC circuit breakers are introduced. Then, soft-closing strategy of hybrid DC circuit breakers based on transfer branch group-by-group conduction is proposed, and two kinds of basic transient process of soft-closing strategy are analyzed. Through the analysis on the transient processes of different closing/reclosing applications, it is concluded that the proposed soft-closing strategy can reduce the overvoltage during closing/reclosing operation and realize the converter station starting from the DC side without any pre-change circuit. In addition, a soft-closing overcurrent protection method and energy balance method of energy dissipation branch are proposed to improve the soft-closing strategy, which can effectively reduce the breaking current when closing to fault and the energy imbalance of the energy dissipation branch. Finally, the validity and feasibility of the presented soft-closing strategy, and the soft-closing overcurrent protection scheme and energy balance metho are verified through PSCAD/EMTDC simulation analysis.

In order to ensure the safety of construction stringing and obtain the continuous change data of the parameters such as the load of the pulley and the sag of the observation sections during the tension stringing process, a calculation method for the continuous process of tension stringing based on catenary method is proposed. According to the tension stringing system model, the tension stringing system equations are established, including the height difference and span equation between nodes, the balance equation of the traction board, the tension balance equation before and after the pulley, and the construction control equation. The continuous iterative method is proposed to realize the continuous motion analysis of the whole process of the traction board from the tensioner to the tractor, which can accurately calculate the tension of tensioner and tractor, sag between the various sections, load of the pulley and envelope angle of the conductor passes through the pulley. A tension stringing engineering test is carried out in transmission line, data such as the load of the pulley and the sag of the observation sections during the construction process is measured, and the calculation results are compared and analyzed to verify the accuracy of the calculation method. The calculation method of continuous process of tension stringing proposed is simple in form, easy to be realized by program, and has high calculation accuracy. It can provide more accurate calculation basis for the selection of construction equipment and process control of tension stringing, and guide the tension stringing construction.

In order to improve the arc-quenching capability of jet stream arc-quenching lightning protection gap, it is very important to understand the arc-quenching principle and the influence of the controlled length of airflow channel on the arc-quenching process. This paper analyzes the feasibility of the jet stream to extinguish the arc from the perspective of energy balance, and deduces that the velocity of the airflow is positively correlated with the controlled length of airflow channel, and that increasing the controlled length of airflow channel can promote the airflow development, enhance convective heat dissipation power, accelerate arc cooling, and thus improve the arc-quenching efficiency. A two-dimensional geometric model of the arc-quenching channel is built through COMSOL Multiphysics simulation platform, and simulation of the arc discharge heat transfer process under the coupling of airflow is carried out, the effectiveness of the arc-quenching device is verified. Then the variable of the controlled length of airflow channel is altered to obtain the corresponding simulation results for comparative analysis. Finally, the arc-quenching experiment is setup for verification. The results show that extending the controlled length of airflow channel can extinguish the arc and inhibit arc reignition more quickly and effectively, further optimize the arc-quenching performance of the jet stream arc-quenching lightning protection gap.

Material industry is one of the sources of energy consumption and pollution emission. The study of environment-friendly materials and the real realization of sustainable development of materials play a vital role in reducing the waste of resources and energy, controlling pollution emission and protecting the environment. This article introduces the degradation mechanism and design of thermosetting insulating materials from the perspective of resource recycling, and discusses the research and application of thermoplastic polyolefin materials. And from the perspective of reducing pollution emissions, the research progress of halogen-free flame-retardant polymers is described.

The overhead transmission line has the characteristics of large span, soft quality and low damping, it is very sensitive to the action of wind load. The buffeting tensions at the junction of the conductor and its end under the action of the fluctuating wind are the most difficult points in the structural design of the transmission line. Based on the theory of random vibration of structure and the mechanics of cable structure, the dynamic response in static equilibrium state is divided into background response and resonant response. The background component determined by using the effect string function is discussed emphatically. The frequency domain analytical solution of the background response power spectrum function and the root mean square of the along-wind dynamic tension (perpendicular to the plane direction of the conductor) are given. The wind tunnel test of full aeroelastic model of two-span 4-bundle conductor is designed and completed. Considering the three connection modes of tensile insulator, I insulator and V insulator. The action law of dynamic tension in wind-induced space is investigated by using high frequency force balance device. The study shows that the influence of different types of insulators on the along-wind tension response is obvious. The nonnegligible aerodynamic damping effect makes the background response account for most of the total dynamic response. At the same time, the relative accuracy of the theoretical model is verified by wind tunnel test.

Because of tight reactive power balance, receiving-end power grid is confronted with serious short-term voltage stability problems. One of the most effective solutions is installing static synchronous compensator (STATCOM). This paper minimizes the investment of STATCOM installation with considerations of network dynamics, power flow constraints, security constraints, and upper and lower limits. The planning of location and capacity for STATCOMs is incorporated into a mixed-integer programming. A convex relaxation method is proposed to deal with the model. In this method, linear superposition method is used to make the model convex with respect to binary variables. Then, a tight relaxation is conducted to the substitution variables to prevent solving mixed-integer programming directly. The example test shows that the investment of the planning in this paper is smaller than that of the conventional method. Additionally, the convex relaxation method has a higher efficiency compared with commercial solvers.

Frequency oscillation belongs to the small disturbance stabilization problem of the active power-frequency (P-F) control process of the power system. The load with voltage regulation effect makes the reactive power-voltage (Q-V) control and P-F control coupled, so the dynamic Q-V control devices can also affect the frequency oscillation. The mechanism and process of dynamic Q-V control devices producing positive damping torque for frequency oscillation through supplementary control are analyzed. Strategy of supplementary damping control is proposed. For fast Q-V control devices with power electronic interface, a proportional link that takes the system frequency deviation as an input is added to the original Q-V control link to provide positive damping for frequency oscillation. A method for evaluating the effect of Q-V control devices at different positions on frequency oscillation is proposed. Selecting Q-V control devices with large effect for supplementary damping control can more effectively increase the frequency oscillation damping. The proposed method is verified with simulations in the New England 10-machine 39-bus system and an actual power system.

A large number of out-of-step separation devices are installed in the tie lines and power plants near the AC transmission section of Guangxi and Guangdong (Guangxi-Guangdong section), and their reliabilities are very important for the security and stability of the main grid of China Southern Power Grid. Based on the actual primary system, this paper constructs an equivalent system model which can accurately locate the oscillation center and calculate the minimum voltage at the measuring point. Dynamic real-time simulation is carried out for various types and different principles of out-of-step separation devices. Typical problems such as unreliable out-of-step locking criterion in fault process and device refusing to move when the oscillation center is located at the device installation point are found and solved at the same time, based on the power grid panoramic simulation test technology and the actual configuration of out-of-step separation devices, the problems existing in the coordination of out-of-step devices near the Guangxi-Guangdong section are comprehensively studied, and the suggestions of putting the wide area out-of-step separation system into operation as soon as possible are put forward. The improvement and optimization measures proposed in this paper have been applied to the actual system.

To respond to the Belt and Road initiative, China Southern Power Grid implements grid interconnection with neighboring countries actively, including international synchronous interconnection by AC transmission lines. The safe and stable operation of international interconnected power grid is related to national image and political livelihood. Moreover, the power systen operation information of the connected countries may not be shared fully, which increases difficulty of the international interconnected power grid operation. In this paper, based on the transient angle stability mechanism of multi-machine power system, the effect of completeness of interactive information on transient angle stability is showed. Considering the special case of incomplete interactive information, transient angle instability criterion based on key dynamic characteristic information is studied, then a adaptive switching control strategy for transient angle stability based on completeness of interactive information is proposed. This work provides technical support for the safe and stable operation of international interconnected power grid.

With the rapid development of distributed power supply in distribution network, the coupling between provincial and local power grids has been greatly enhanced. An asynchronous power flow calculation method for provincial-local coordinated operation is proposed. Considering the communication delays between provincial and local dispatching centers, this paper introduces the concept of “partial synchronization” to replace the traditional synchronous provincial-local power flow calculation. Furthermore, a historical-data-based equivalent method for distribution networks is proposed. When non-instantaneous interruptions occur between provincial and one local dispatching center, the provincial dispatching center can establish an approximate model of this distribution network based on the historical data received from the local dispatching center. Polynomial fitting is used to establish a surrogate function between boundary nodal power injections and nodal voltages, and the provincial dispatching center can independently accomplish transmission power flow calculation with the surrogate function under communication interruptions. Numerical experiments show that the proposed asynchronous method can achieve the same accuracy compared to the traditional method and significantly improve efficiency. Also, the proposed surrogate model can satisfy the accuracy requirements.

With the development of Internet of Things, the network security problem of smart substation has been widely concerned. In the face of information physical equipment failure, virus intrusion and other threats to network security, this paper proposes an anomaly detection method for smart substation network based on deep reinforcement learning. Firstly, combined with the characteristics of smart substation, the automation network architecture of smart substation is constructed, and the application scope of manufacturing message specification (MMS), general object-oriented substation event (GOOSE) protocol, sample value (SV) message, message queue telemetry transmission (MQTT) protocol and limited application protocol (CoAP) are defined. Then, the communication packets in the smart substation network are preprocessed to obtain the traffic characteristics which can reflect the abnormal network. Finally, deep reinforcement learning is used to judge whether the real-time data packets are abnormal. The detection results of each MMS/GOOSE/SV/MQTT/CoAP packet are saved as log records, and the records are added to the learning model to improve its detection performance. The experimental results based on the typical 110 kV smart substation automation system show that the proposed method can accurately detect the abnormal network traffic, and compared with other methods, its false alarm rate is the smallest and the delay is the shortest, so it has a good application prospect.

The correlation between the distributed energy power market and the power grid makes it impossible to ignore the matching problem between transaction and dispatch. The policy of “charging the load side with the wheeling cost” affects the balance of the interests of market participants. Under the traditional centralized energy trading mode, there are trust problems among the transaction subjects and between the subject and the centralized trading platform. For this reason, this paper constructs a distributed energy and electric power transaction matching model considering the real-time market supply and demand, transaction and scheduling matching, and the approval of wheeling cost. The intelligent contract of energy trading mechanism for allotment is designed. This paper proposes a distributed energy power market trading method based on blockchain. The simulation of Ethereum’s Private Blockchain example shows that the proposed method reflects the idea of nearby trading encouraged by the policy, protects the interests of the inferior party under different market supply and demand conditions, and maximizes the preferential rate and transaction rate of the superior party participating in the market.