Several large-capacity VSC-HVDCs feeding into the same receiving-end load center will add the local power flow and raise short-circuit current level, and will have a great impact on the AC system when the VSC-HVDC system is down because of fault. In order to scatter the VSC-HVDC dropping points and reduce the difficulty of the DC power consumption in the AC system of the receiving end, this paper comes up with two split-pole feeding ways of VSC-HVDC, in which two poles are connected to two different voltage-level AC grids and two poles are connected to two inverter stations. Firstly, this article theoretically analyzes the impact of split-pole feeding methods on the VSC-HVDC control and protection system. Secondly, pole-to-pole interaction factor is introduced for the first time to prove that the VSC-HVDC split-pole feeding methods can reduce the mutual influence between the positive and negative poles. Finally, the fact that the DC split-pole feeding method can indeed improve the safe and stable operation level of the system is verified by simulation in PSCAD.

The distribution area equivalent load dynamic model is an important foundation for accurate sensing and precise control in distribution network. Based on feeder voltage regulating equipment and distribution phasor measurement unit, the load dynamic model of distribution area can be identified online. This paper discusses this identification work deeply, and reveals its closed-loop identification essence from the mechanism. The transfer function of direct closed-loop identification is derived and the main factors affecting identification precision are introduced accordingly. Aiming at the poor accuracy of direct closed-loop identification, a two-stage closed-loop identification combined with augmented least square method is used. In this method, the closed-loop identification is transformed into two open-loop identifications and the noise model is identified synchronously to reduce the identification error. Based on simulation, the influence of the capacity, electrical distance and load structure on the identification error are analyzed. The simulation also verifies the effectiveness of two-stage closed-loop identification to reduce the identification error.

The multi-energy system is a kind of energy organization form which can realize the energy consumption terminal supply efficiently, cleanly and economically. It integrates many kinds of energy conversion and transmission, so the traditional power flow analysis and calculation method is no longer suitable for coupling equipment and thermal flow simulation. This paper presents a hybrid power flow calculation method suitable for terminal multi-energy supply. Firstly, the Sukhov cooling operator in the heat supply network is simplified, and then the mathematical description of power, heat and hydraulic flow is developed. On this basis, the mathematical model of Newton Raphson fast iterative solution algorithm is established by using the improved cooling operator, and the value of Jacobian matrix elements affected by the electric-thermal coupling is derived. Finally, an example of a regional electric-heat supply system is given to verify the effectiveness of this method.

The characteristics of the transaction price of large-scale cross-regional power market are quite different from that of provincial market. Based on the optimal distribution of diversified energy resources across regions in a large range, this paper proposes a market price mechanism design for coordinated distribution of multi-energy resources across regions. This paper focuses on the optimal distribution model of diversified energy resources. Firstly, all power sources and power generation resources are combined and unified, and a two-layer optimization model including multi-energy coordination and optimal distribution among regions is proposed. Secondly, a two-layer optimal matching model of electric energy and other power generation resources is established, and a particle swarm optimization algorithm for node matching coordination is proposed for multi-energy optimal allocation. Thirdly, particle swarm optimization and linear programming are used to optimize the distribution of other power generation resources in the transportation network. Finally, an example is given to verify the feasibility and effectiveness of the proposed model.

In the large-scale cross-regional power market, the transmission price of “one price for one line” is difficult to promote the optimization of resource allocation. Meanwhile, energy transmission and loss are closely related to energy sources and routes. This paper proposes a nodal price mechanism based on transmission fee apportionment and energy volume decomposition. Firstly, a transmission pricing method based on megawatt hour kilometer apportionment is proposed to make transmission pricing only related to distance and transmission volume, thus enhancing the fairness of transmission price for every participant. Secondly, a method of down-stream decomposition of energy quantity based on path tracing is proposed. By tracing the energy distribution results, the decomposition sequence and downstream decomposition are determined to clarify the source and path of energy quantity, so as to calculate the energy loss price and form the final node price. Finally, an example is given to verify the effectiveness of the proposed mechanism.

In view of the safe and reliable transmission, processing and storage of smart meters and the cloud platform of metering master station in power Internet of things, a smart meter billing management model based on cloud security and homomorphism password in Internet of things environment is proposed. Firstly, network security detection based on cloud security is helpful to strengthen the security protection of smart meters in Internet of things environment. Secondly, homomorphic asymmetric key encryption technology is uesd to encrypt and upload customer data to the cloud, and allow the cloud to obtain the total energy consumption of users in a given period of time without decryption operation, so as to strengthen the protection of user privacy and data confidentiality. After that, combining Amdahl’s law and user-defined acceleration measurement, a parallel accounting algorithm is formed, which can fully improve the processing capacity of multi-core processor in cloud servers. Experimental results show that compared with the existing methods, the proposed model can significantly reduce the time required for smart meter billing and enhance the security protection and information processing capacity of smart grid on the premise of ensuring user privacy and data security.

Lightning is the main cause of transmission line failures. In the past, passive lightning protection and real-time monitoring of lightning through the lightning location system are mainly used in transmission lines. However, early warning of lightning risks in line corridors is not possible. This paper proposes an active early warning method for lightning risks of line corridors based on combined radar reflectivity in consideration of meteorological factors and grid factors. Firstly, the combined reflectivity product covering the entire Guangdong region with a spatial resolution of 1 km×1 km is obtained through network puzzles and matchs with ground flash sample data in the “Easy Flash Corridor”; secondly, based on Gaussian mixture model, the sample data Perform fitting and classify the lightning risk level; Thirdly, the Pearson correlation coefficient between the extrapolated fusion product and the actual situation is analyzed and passed the significance test; Finally, the effectiveness of the proposed method are verified by analyzing actual cases.

In this paper, based on the high speed schlieren technology, the test observation platform of long gap discharge process and channel insulation recovery process is set up. The synchronization strategy is put forward too. Voltage, discharge current and schlieren pictures observation in the discharge process and channel insulation recovery process are conducted synchronously. Spherical shock wave at the discharge channel and electrode contact point and cylindrical shock wave along the discharge channel are discovered after the long air gap breakdown. Through statistics, the curve of cylindrical shock wave propagation speed and radius of the shock wave, and the influence law of the applying different voltage type to shock wave velocity are obtained.

In the converter valve assembly, the inner surfaces of the different aluminum radiators in cooling water system have different potential, which have an important impact on their corrosion. It is of great significance to study the corrosion mechanism of the deionized water on the inner surface of a aluminum radiator, so as to prevent electrode corrosion in the cooling water system of the converter valve. In order to study the corrosion current formation mechanism of aluminum electrode, the reverse thinking is used to simulate the surface of the aluminum radiator and the deionized water system surrounded by the aluminum electrode in the converter valve. Based on the quasi-static current field, an iterative analysis model of the current density on the surface of the aluminum electrode with and without the electrode dynamic characteristics is established. The anode and the cathode surfaces of aluminum are analyzed iteratively, and the current density distribution on the surface is also analyzed. The equivalent circuit of the suspended aluminum deionized water electrode system is proposed and established. The results show that the area of the suspended aluminum anode accounts for 73% of the total surface of the aluminum electrode, which is much larger than that of the cathode surface; the simulation current density without considering the dynamic characteristics of the electrode is larger than that of considering the dynamic characteristics of electrode. This study provides an important research basis for the study of the aluminum radiator corrosion in the deionized water of the converter valve.

This paper studies protection principles for a series multi-terminal DC system. The difference between conventional HVDC systems and series multi-terminal HVDC (MTDC) is analyzed from protection aspect. The problem of conventional protection principle applied in serial MTDC has been investigated. In order to supply main and back up protection with high reliability, high sensitivity and fast operation speed, a travelling wave protection solution based on the rate of changes in the local measured signals together with modified DC filter configuration is proposed in this paper which can be used as the main protection of the transmission line in series MTDC grid. Simulation on PSCAD model verifies the validity of the proposed solutions.

The precise fault range measurement of the four-circuit line of the mixed tower is difficult because of the coupling between the lines. In this paper, the asymmetric impedance model closer to the actual engineering is introduced, and two impedance decoupling matrices M₁ and M₂ with different physical meanings are introduced. The reverse zero-order g₀ sequence network in the two decoupling modes has the same network topology. The external sequence impedance and the sequence voltage are both 0. The sequence current flows only inside the four loops and is not affected by external devices. Therefore, the g₀ sequence network is uniformly used, and the one-step distance measurement equation is established from the two busbars to the fault point, and the fault ranging of the four-circuit line of the mixed-pressure tower is transformed into a single-sequence network, which greatly simplifies the complexity of the fault location of the four-circuit line of the same tower. A large number of PSCAD/EMTDC experimental simulation data show that both algorithms can achieve accurate ranging, and are not affected by system operation parameters such as fault distance, transition resistance and power angle difference.

In this paper, a parameter setting method of grounding distance protection for transmission line based on positive sequence impedance is proposed. By analyzing the ratio of the inductive impedance and positive sequence impedance in extreme cases, the setting value can be obtained directly from the positive sequence impedance to realize the decoupling between the setting value and the line mutual inductance, simplify the setting principle of distance protection, and realize the transformation of setting calculation from complicated short-circuit current calculation to simple parameter setting. This paper analyzes the location of each section of distance protection, and puts forward different setting strategies for the same tower line and the non same tower line from the perspective of engineering application. Finally, an operation line example is given to show that the method is simple and feasible, and has strong adaptability and engineering practicability. Based on this method, a prototype of line protection device has been developed and applied to Guangdong Power Grid.