Under the background of the new power system, parameter identification and correction based on measurement data are key requirements for the digitalization and intelligence of distribution networks. A parameter identification method is proposed that integrates the mathematical model of the distribution network with measurement data collected from the low-voltage side of distribution transformers, aiming to address the online identification and correction of line and transformer parameters. Firstly, the topology is obtained by parsing CIM files, and the initial parameters of components are set according to asset data. Then, a quasi-Newton-Raphson method is employed to construct the Jacobian matrix based on multiple sets of measurement data, enabling iterative parameters updated by solving underdetermined or overdetermined equations. Finally, the identified parameters are used to recalculate the low-voltage side voltages, which are then compared with the measured values for validation. Experimental results based on data from a practical distribution network in South China demonstrate that, with increasing data sets and iteration times, the average relative errors converge to a stable level. This verifies that the proposed method achieves high accuracy and practicality, and can provide effective support for power flow calculation, state estimation, and digital twin construction in distribution networks.

The cryptographic device generates a large amount of physical information such as electromagnetic，energy consumption，heat，etc. during encryption and decryption. The attackers use these physical information to perform a side channel attack on the cryptographic device and steal the key of the cryptographic device. In the case of a traditional simple power analysis attack of elliptic curve cryptography algorithm，the attacker recovers the key by manually identifying similar modules in the power consumption data of the double point calculation. But this way results in low attack efficiency and low attack accuracy. This paper proposes the SPAMD algorithm based on the time series of motif discovery. The algorithm realizes the automatic recognition of similar modules in the power consumption data of the double point calculation，and completes the conversion of the attack mode from manual recognition to automatic recognition. Experiment results show that SPAMD attacks have a significant improvement in efficiency and accuracy.

Along with the growing integration of renewable energy resources, the new power systems, which are dominated by inverter-based resources （IBRs）, are facing critical challenges in both planning and operation stages. The conventionally used system strength metric, short-circuit ratio （SCR）, exhibits limitations in assessing connections of new IBRs due to their unique dynamic behaviour and control interactions. In this paper, the definition of system strength is reviewed. The underlying principles of conventional SCR and its variants are then discussed, with their constraints explained. To describe the system strength in a more comprehensive way, this paper further classifies system strength into three categories: quasi-static, small-signal, and large-signal. For each category, relevant metrics are introduced and their relative merits are discussed. Electromagnetic transient simulations are presented to illustrate key insights.

When interior point method is used to solve the problem of reactive power optimization in large scale power system, the feasible solution may not be obtained because of the unreasonable part of the constraint conditions. In this paper, a practical relaxed reactive optimal power flow method (Relax ROPF) is proposed to restore the solvability of reactive optimization by interior point method. In the iterative process, the ill-condition constraint which causes failure of OPF can be automatically identified, the problem is restored by introducing minimum relaxation into those ill-condition constraints. Test results on IEEE 39-bus system and an actual power grid show that the proposed method can identify unfeasible constraints very well, and can effectively restore the optimal power flow.

Aggregating clean energy and energy storage access to the grid can effectively reduce the impact on the safe operation of power grids caused by decentralized access. However, the focus of future research on clean energy participating in market competition lies in improving the revenue of aggregated clean energy and energy storage. This paper aggregates clean energy and energy storage as an aggregated regulation generation unit （AGU）, and studies its bidding strategy on day-ahead power market. Firstly, a power market clearance model using queuing clearing method is established, and then the optimization model of bidding strategy based on evolutionary game theory is constructed. Secondly, the cost-benefit model of AGU is constructed to determine final bidding strategy. Finally, the arithmetic examples are analyzed using relevant data from the electricity market in Zhejiang Province and then a comparison is made with traditional bidding strategies, which verifies that the proposed strategy can improve the revenue of AGU.

Driven by the "dual carbon" goals and energy transition, distributed photovoltaic systems with their characteristics of "numerous points and extensive coverage" are connected to distribution networks, making power interactions between distribution network levels more complex. Traditional supply-side regulation methods struggle to meet the operational demands of multi-source collaboration and multi-objective coordination. To address this, a multi-level multi-objective collaborative optimization method for distribution networks-substation areas-users is proposed, considering dynamic comfort zones. Firstly, a multi-level structure and hierarchical scheduling framework for distribution networks, transformer areas, and users is established. The distribution network is divided into the distribution network layer, transformer area layer, and user layer. Within each layer, source-grid-load-storage resources achieve collaborative interaction, while bidirectional power transfer and information exchange occur between layers, promoting rational resource allocation and utilization. Secondly, a flexible resource model incorporating dynamic comfort zones is developed to quantify residential users′ resource regulation potential under varying electricity prices, enabling real-time adjustment of regulation boundaries. Then, a multi-level multi-objective collaborative optimization model for distribution networks-substation areas-users is formulated, comprehensively considering optimization objectives across different levels to establish a bottom-up coordination mechanism. Finally, the proposed strategy is validated through case simulations. The results demonstrate that the method effectively maximizes and utilizes source-grid-load-storage resources across all levels, significantly improving photovoltaic integration, optimizing load curves, reducing user electricity costs, and ensuring safe and economical distribution network operation

The development and test of China’s first ±525 kV cross-linked polyethylene （XLPE） DC cable are introduced. A type of heteromorphic copper conductor with a section of 3 000 mm² was designed， and a water-blocking tape was chosen as filler material. After calculation， the filling factor of the conductor reached 95.5%. Longitudinally permeability tests on the insulated conductor have proceeded under the condition of 2 MPa hydraulic pressure for 10 d and 1 m water column with thermal cycling for 10 times， the length of permeability was 7.2 m and 0.9 m respectively. Copper wires were twisted as a metallic shield of the ±525 kV XLPE DC cable， among the copper wires， two optical fibers were implanted in to achieve the requirements of communication and thermometry online. A composite waterproof sheath was compounded with aluminum-plastic tape and PE， hence， the outer diameter of cable has been minished 10% compared to corrugated aluminum-sheathed cable in the same voltage and section. To verify its electrical properties， voltage test and partial discharge test under AC 525 kV were carried out， then a whole performance type test was taken in National Center of Testing and inspection for Electric Cable and Wire （TICW） referred to CIGRE TB496—2012 and GB/T 31489.1—2015， including load cycle test， DC withstand voltage test， superimposed impulse test and so on， and the conductor passed all the tests. During the load cycle test， the maximum temperature of the conductor was over 70 ℃， and the temperature gradient in insulation exceeded 30 ℃.

Traditional communication technology between substations of security and stability control (SSC) system has some inherent shortcomings, it does not conform to the trend of current technological development and restricts the expansion and application of SSC. Using intelligent substation process layer GOOSE communication technology, a new communication technology between substations based on IEC 61850 in SSC is proposed in this paper. The key technology of communication network architecture, communication capacity control, data flow control and visualization of decoupling configuration are deeply researched, and the typical project of Brazil Belo Monte SSC application is introduced. This technology has several advantages, such as stable and reliable communication, data transmission capacity, reusability and interoperability. It can meet the demand of information exchange between substations, and it represents the development direction of the communication technology of SSC.

Ultra-high-penetration distributed photovoltaics （PV） in distribution networks pose significant challenges, including severe reverse power flow overloads and voltage violations. Addressing the strong coupling characteristics between active-reactive power （P/Q） and voltage under complex network impedances of distribution networks, a active-reactive power coordinated voltage support optimization method is proposed. This method achieves multi-objective collaborative optimization operation of distributed renewable energy and energy storage, balancing low operational costs with high power quality. Firstly, a rolling optimization method for three-phase power flow voltage model predictive control （MPC） based on active-reactive power coupling is proposed. Via a multi-period voltage MPC framework, the number of decision variables and constraints is effectively reduced, which improves solution efficiency while ensuring solution accuracy and achieves fast solution of the online voltage control problem. Furthermore, a pre-iterative method based on fixed-point iteration is proposed for the strongly coupled three-phase power flow model. By distributing multi-step iterations across the rolling optimization horizon, the solution accuracy is significantly improved without increasing the number of per-step iteration. Finally, the effectiveness of the proposed control system in suppressing voltage exceeding limits is verified by integrating an IEEE 13-node system with ultra-high-penetration PV.

With the continuous expansion of electric taxi fleets in various cities, their large-scale and unregulated charging behaviors will not only aggravate the fluctuation of the power grid load curve, threaten the stability and security of the power grid, but also reduce the equipment utilization rates of remote charging stations. Therefore, an electric taxi orderly charging guidance system is established based on the information cooperation of “vehicle-station-network”, which proposes a spatiotemporal bi-level charging optimization of electric taxi considering the feasibility of user participation in scheduling. In the temporal level model, a multi-objective optimization model is established based on minimizing the peak-valley difference, standard deviation and the charging cost of users. This model optimizes the charging time load of electric taxis in advance and reserves charging time windows for each user. In the spatial level model, real-time scheduling of the spatial load of electric taxi charging is carried out with the objectives of balancing the average utilization rate of each charging station and minimizing users′ charging time cost, in order to allocate the optimal charging station for each user. Finally, the effectiveness of the proposed optimization strategy is verified through a case simulation, demonstrating its ability to balance the interests of power distribution network, charging station operators and electric taxi users.

Aiming at the practice of intelligent robot inspection of transmission lines, four key control technologies of the robot’s automatic inspection operations are developed including automatically passing over obstacles, automatically positioning, automatic fault diagnosis and restoration, automatic inspection The principle and implementation method of the control technology are introduced in detail. Three typical failure modes of the robot, i.e., the self recovery fault, the replacement fault and the fault need to repair, and their diagnosis and repair strategies are established. The robot inspection test on real outdoor line is carried out. Robot inspection demonstration application of 500 kV live line in China Southern Power Grid is completed for the first time. The robot inspection control technology, fault diagnosis and repair strategy, as well as the independent inspection process are verifid and assessed. The robot has a single time inspection mileage of over 10 km, and the inspection application has achieved good results.

Driven by the "dual carbon" goals, the user side of the new power system faces multidimensional security risks due to the large-scale integration of new grid-connected entities such as distributed photovoltaic systems, electric vehicle charging stations, and energy storage equipment.Firstly, the challenges to equipment safety, grid security, and societal safety posed by the massive integration of these new entities are systematically analyzed, core bottlenecks at the technical and managerial levels, such as uneven equipment quality, difficulties in cross-modal data fusion, and insufficient safety protections, are highlighted. To address the heterogeneity, semantic differences, and correlation characteristics of multimodal data, a multimodal large model construction technology is proposed, incorporating data augmentation generation, cross-modal semantic alignment, and parameter-efficient fine-tuning methods to enhance risk perception accuracy. Furthermore, integrated security prevention and control strategies are introduced from three perspectives: grid optimization, intelligent operation and maintenance, and resilience enhancement. These measures provide theoretical support and practical pathways for the security governance of the new power system, facilitating the coordinated development of energy transition and security under the "dual carbon" objectives.

The wide area response based transient stability detection and control technology has become a hot research area in power system stability studies. Currently several different technologies have been proposed, but lots of problems still need to be solved before they can be applied to practice. In order to effectively analyze and compare the validity and practicability of these transient stability detection technologies, a wide area measurement system (WAMS) based prototype system is developed for power system real-time transient stability detection and control. Based on real-time measured data from PMU, the system simultaneously implements various response based transient stability detection and control technologies and provides visual presentation of results. The design of framework structure, implementation of function modules and engineering applications of the system are presented. Meanwhile, suggestions on future orientation of wide area response based transient stability control are given in the following aspects including time delay, data acquisition and control schemes generation. Engineering application demonstrates that the prototype system has a good perspective and is an effective tool for analysis and comparison of the wide area response based transient stability detection methods.

In power market environment, the competition mechanism has been extended to the distribution side. Distribution company regulation methods for market competition have become important research the topics of power market reform. In this paper, the methods of distribution regulation the power market environment, involving the traditional rate-of-return regulation method, the revenue-cap regulation method, the price-cap regulation method, the yardstick competition regulation method and the quality regulation method, together with their advantages and disadvantages are summarized. Finally, the experiences of distribution company regulation in the world are discussed, which provides a good reference for the adjustment of regulatory approach and the establishment of a modern electricity regulatory system in our country.

With the proposal of dual-carbon target, energy storage is an important way to promote distributed PV local balanced consumption and reduce carbon emissions from the distribution network, but the traditional energy storage configuration scheme usually only considers the electric power balance, and how to comprehensively consider the electric-carbon characteristics puts forward higher requirements for the optimal configuration of energy storage. Firstly, a cluster division method based on electrical distance and net load carbon flow rate is proposed by introducing the node net load carbon flow rate index for cluster division of distribution networks, which improves the efficiency of distribution network management and the accuracy of carbon emission management. On the basis of the cluster classification, an energy storage allocation method that takes into account the carbon emission cost of the distribution network is further proposed, which takes into account the carbon emission cost and network loss cost, as well as the economic cost and benefit of energy storage allocation, establishes a carbon balance mechanism for energy storage, quantifies the impact of the change of the carbon content within the energy storage on the distribution network, and avoids carbon dioxide emissions into or out of the energy storage equipment. Finally, the results of an arithmetic simulation in a distribution network in Anhui province show that the proposed method reduces the total carbon emissions of the distribution network by 11.12 % compared to the unconfigured energy storage system.

With the increasing complexity of "high-proportion renewable and high-electrification" power systems, traditional model-driven stability analysis methods face growing limitations. Artificial intelligence （AI） techniques, offering advantages in both speed and accuracy, have emerged as a key research focus. This paper focuses on the development path of power system stability analysis technology from model driven to data-driven, and further to hybrid intelligence integrating domain knowledge and data. Firstly, the technical requirements of typical stability analysis tasks are outlined, and traditional model driven methods are reviewed.Subsequently, the application results of artificial intelligence methods in different scenarios are summarized, and their advantages and disadvantages are analyzed. Further the information driven methods and research progress of integrating power system knowledge and mechanisms are explored. Finally, based on the power system characteristics under the background of "double high", the current challenges faced are analyzed, and future research directions are discussed.

With the large-scale application of new power electronic devices in power grid， the risk of harmonic resonance is higher and higher. However， the design of trip criterion of security and stability control （SSC） device in the past seldom considers the new harmonic condition. Combined with the actual harmonic resonance happened in CSG， this paper carries out the study of harmonic impact on SSC device. According to defects found in studies that SSC device can’t effectively filter out specific frequency of high order harmonic， sampling algorithm of the device is analyzed theoretically， and harmonic impact of no-fault line trip criterion is also analyzed under existing conditions. Combined with the actual SSC devices in CSG， a temporary measure to deal with the risk of refusing action of SSC device is put forward. Also an ultimate optimization method of SSC software and hardware is proposed and tested on the SSC test platform. Test results verify the effectiveness of the proposed method， and meanwhile the method has important significance to the design and improvement of other SSC devices.

The sub-synchronous oscillation （SSO） incidents caused by the dynamic interactions between wind farms and the rest of power system threaten the safe and reliable operation of practical power grids. Firstly， this paper introduces several incidents occurred in practical power systems caused by wind farms， and several key factors of wind turbine types， mechanism， and the consequences are described. Secondly， the paper illustrates the commonly used analysis methods which are frequency-domain method （complex torque coefficient analysis and impedance-based method） and model analysis method for analyzing SSO caused by grid-connected wind farms in terms of principles， applicability， and characteristics. Thirdly， the paper summarizes the researches which have been carried out in the area of SSO caused by grid-connected wind farms on the basis of the analysis methods and the object system types adopted in the literature. In addition， the current research status of mechanism investigation on the issue of SSO caused by grid-connected wind farms has been demonstrated. Finally， the analysis methods and issues to be addressed urgently for mechanism study of SSO caused by grid-connected wind farms are discussed.

In order to improve the efficiency of electric vehicles (EV) participating in logistics distribution and to avoid the impact of massive disordered charge on safe operation of the distribution system, this paper presents a charging service fee model based on real-time traffic information sensing by crowd sensing technology to achieve the messages about real time traffic status and charging station information, and proposes a waiting time estimation model in the charging station based on queue theory. Considering the constraints of route selection, time, battery capacity, cargo capacity and operating voltage in distribution system, this paper constructs a model of EV path optimization and charging navigation which minimizes the sum of logistics travel time cost, waiting time cost, battery depreciation cost and fast charging cost. A comprehensive numerical simulation is conducted on the 33-node logistics distribution system in a city center within 50×50 km zone. The results show that considering the real-time information sensing can reduce the logistics distribution cost effectively and alleviate the harmful effect on distribution system operation stability.

The mechanism of the effects of external short circuit current on oil flow inside the transformer is analyzed, and a SFPZ11-120 MVA/220 kV transformer transient electromagnetic-force-flow field coupled model is built in ANSYS Workbench. The vibration of windings caused by short circuit current is studied, and the effect of external fault on transformer oil surge is simulated accurately by finite-element method, from which the distribution of oil flow under external faults can be achieved. The simulation results show that the transformer oil surge caused by external short circuit current has great effect to gas protection, which may cause gas protection maloperation.The simulation models and methods can be generalized to oil transformers of other voltage level and can provide reference to analysis of transformer oil surge.

With the growing integration of renewable energy, load frequency control （LFC） in power systems faces security risks from false data injection attack （FDIA）. Existing detection methods struggle to differentiate control input attacks from measurement attacks, compromising system stability and security. This paper develops a state-space model for LFC incorporating renewable energy and energy storage systems and analyzes the impact of FDIA on system dynamics. A state-space decomposition method is employed to decouple attack signals into control input and measurement attacks, improving detection accuracy. A sliding mode observer-based attack estimation method is proposed for real-time detection. Additionally, an attack-resilient control （ARC） strategy is designed using H_{\mathrm{\infty }} control theory to enhance system robustness. Simulations show that the proposed method reduces the attack estimation mean squared error by nearly 30% and significantly improves frequency response stability compared to traditional methods. These results demonstrate the method′s effectiveness in detecting FDIA and enhancing power system security.

As a new type of operation and maintenance mode for transmission lines, helicopter patrol inspection has the advantages of high efficiency, good effect, etc. However, its large-scale application should be based on the premise of safety operation. In this paper, a safety risk assessment model of helicopter inspection is established by using risk matrix, in which the safety risk factors of the whole operation process are analyzed from the aspects of personnel, equipment and environment. The risk value is determined by the risk probability and the consequence severity, and then the risk level of each risk factor can be assessed according to the position of the risk value in the risk matrix. Differentiated risk control measures are proposed to avoid high-risk operations and provide a favorable support to ensure the safety of power grid, operating personnels and equipment.

Based on Volterra online parameter identification method, by means of digital simulation, dominant parameters identification, model substitution, as well as external response characteristic comparison, the equivalency and adaptability of using ZM model to represent ZIP model or ZIPM model are investigated. Simulation results show that, when the proportion of constant impedance load of ZIP portion in ZIPM model is greater than 70%, the external response characteristics of equivalent ZM model are similar to the ZIPM model, and can satisfy the requirements of electromechanical transient simulation.

Featured with long distance, large capacity, extra high voltage and AC-DC interconnected operation, China Southern Power Grid is interconnected with surrounding areas and countries through multiple AC lines, and has complex operation characteristics. In combination with the operation practice of Southern China regional power system during recent years, the operation characteristics of complex AC-DC interconnected power grid is discussed in depth. This paper reveals the main security risks in the operation of Southern China regional power system, including: the prominent risk of single-cause common mode fault, the prominent stability problem caused by the primary and secondary equipment failure in the AC-DC close coupling scenario; and the security of main power grid caused by the stability problems of frequency and rotor angle seriously. On the basis of summarizing the stability control methods, this paper proposes to build the power system security and stability defense lines based on wide-area information, which will make the China Southern Power Grid more secure and stable in the future.

The rapid fluctuations in renewable energy output cause frequent voltage oscillations in power grids, severely threatening the safe and economical operation of power grids. To address this issue, a real-time reactive power optimization method based on graph convolutional networks （GCN） is proposed. Firstly, a multi-objective reactive power optimization model considering the importance of nodes is constructed. Based on this, the graph representation of the reactive power optimization model is established, and the adjacency matrix is restructured in conjunction with the optimization problem. Then, the optimal solution set is mapped using the GCN algorithm, and the improved CRITIC-AHP-TOPSIS combined weighting algorithm is employed to select the optimal solution, forming a real-time optimization strategy. Finally, using the modified IEEE 39-node system and an actual power grid as examples, the proposed method is verified. The results show that the method not only has the advantages of fast solving speed and avoiding local optima but also achieves more favorable voltage deviation and active power loss, ensuring the safety and economy of new power system operation.

The construction of a high proportion of new energy power systems is accompanied by a reduction in inertia/primary frequency regulation(PFR) resources with conventional synchronous machines. In order to address this, it is necessary to consider the construction of ancillary service market with multiple type resources to provide inertia and primary frequency regulation. In this paper, a two-stage joint clearing mechanism considering multiple type resources electrical energy and inertia/PFR ancillary service is proposed, and a joint clearing optimization model including energy storage, wind power, photovoltaic and frequency-supported loads is established. The capacity of all kinds of ancillary service resources required by the system and the start and stop of each resource are solved in the security constrained unit commitment(SCUC) pre-clearing model considering the frequency security constraints. In the formal clearing model, the simple inertia and the demand constraint of PFR ancillary service capacity are considered, and the market pricing is simpler and more transparent taking into account frequency security. The simulation results of the improved IEEE 39-node system demonstrate the effectiveness of the proposed two-stage market clearing mechanism.

DC voltage divider is an important measurement equipment in converter station, the insulation failure of DC voltage divider will directly affect the operation of HVDC system. Two typical insulation faults of ±800 kV DC voltage divider are described, the disassembly status and insulation structure are discussed, and the potential and electric field distribution under different operating conditions of the voltage divider are calculated and analyzed, then the cause of faults is proposed as follows: under wicked external insulation operating environment, the insulation resistance of polymeric housed epoxy cylinder of the voltage divider nonlinearly declined, which makes the axial resistance of epoxy cylinder and resistance capacity units unsuitable, and further results in axial potential difference and causes partial discharge, creeping discharge of the epoxy cylinder, and radiate partial discharge and SF₆ gas-gap breakdown of the voltage divider. Based on the above analysis, the countermeasures are proposed such as improving the external insulation potential distribution, enhancing the threshold of partial discharge and breakdown, and carrying out the specific operation and maintenance. The research achievements will be of great significance to the selection and operation maintenance of DC voltage divider, and the improvement of operation reliability of ±800 kV DC voltage divider.

Based on typical structure of voltage source converter based HVDC (VSC-HVDC) station and its parameters, the impact of startup process of VSC-HVDC station on AC grid is analyzed in this paper. According to the characteristic of voltage and current during station startup, it is concluded that AC grid voltage might drop abruptly because of transformer excitation inrush current or incomplete charge of DC capacitors at the time of closing AC circuit breaker or bypassing charging resistor. A control method to avoid the voltage drop of AC grid is proposed which decreases over current through phase selection switchs and delayed charging resistor bypassing. The method is verified through simulations based on real VSC-HVDC station.

With the maturity of power cable technology and updating of new technology of cable accessories, the failure characteristics of high voltage cable systems and fault causes have changed significantly. In this paper, detailed statistics are carried out for the characteristics and fault cause proportions of 132 failures for 110 kV and above power cable in China Southern Power Grid(CSG)during 2006 and 2016, and 99 failures in the literatures, and the fault characteristics and main reasons of the high voltage cable system in recent years are analyzed. The statistical results show that the present operation reliability of high-voltage cable system in CSG has been improved significantly, while the failure rate has decreased by an order of magnitude compared to 2001. Cable accessories have now already become the weakest part of high-voltage cable systems, the failures of which account for as high as 85.5% without taking external damage into account. For cable, more than 70% of the cable failures are due to external damage, while more than 84% cable accessories failures are due to product quality and improper installation. The statistical result of power cable system can provide a basis for the development of differentiated operation and maintenance strategy.

This paper investigates the dynamic characteristics of active power and reactive power during HVDC commutation failure period. The quantitative index for assessing voltage supporting capability of AC system for HVDC system is introduced. The influence of simultaneous commutation failures of Guangdong multiple HVDC on the secure operation of the power grid is analyzed from three aspects: AC area where AC fault may cause multiple HVDC simultaneous commutation failure; multi-infeed effective short circuit ratios and the number of power grid instability under severe AC system failure conditions. Technical countermeasures including HVDC control strategy optimizing, dynamic reactive power compensation installation, AC power grid topology reconfiguration and VSC HVDC utilization are proposed for dealing with voltage instability risk of Guangdong power grid.

Capacitor voltage transformer (CVT) is widely applied to electric power system. It is beneficial to acquire the accurate transfer function of CVT for the protection and the monitoring of power system. At present, the reaserches about CVT are based on its typical equivalent circuit, however, due to the different internal parameters of CVT under different operating conditions, the transfer functions are different, which leads to inaccurate research results before. A square-wave pulse is applied to CVT when the internal structure parameters are not clear, then, the recursion method and the least square method are applied to caculate the impulse response of CVT based on convolution theorem, and Laplace transform is used to obtain the frequency transfer characteristics. The correctness of the theory and the reliability of the algorithm are verified by building the simulation circuit in PSCAD. Furthermore, the noise is added in the output signal, the anti-noise ability and noise impact factor of these two algorithms are analyzed in their algorithm structure. It is found that when noise is added, the anti-noise ability of the recursive method and the least square method are influenced by the length of convolution, both methods can get accurate results when the signal to noise ratio is larger than 40 dB.

For solving the common existence of feeder overload problem, a load balance technology based on multi-source data fusion is proposed. Firstly, a feeder overload quantitative model is proposed according to the dynamic characteristics of distribution load. Then, distribution load sets are constructed for the three typical application scenerios based on multi-source data of dispatching, operation and maintenance distribution and marketing. Finally, the optimal feeder load balance adjustment strategy is determined through trail calculation and comparison of the overload indexs of multiple distribution reconstruct schemes. Example shows the effectiveness of this technology. Follow this technology, a distribution load management and optimization assistant decision-making system is developed, which has been practically applied to Jiangsu distribution dispatching, operation and maintenance.

With the rapid development of power grid business and the improvment of management requirement, the current power grid operation smart system zone Ⅲ Web with scattered maintenance/management cannot meet the development requirements of power grid and the requirements of secondary system integration construction of China Southern Power Grid. An integrated power gird operation smart system zone Ⅲ Web scheme based on Citrix is put forward. The feasibility and system architecture of the integrated power grid operation smart system zone Ⅲ Web based on Citrix are given, the key technologies of integrating the current zone Ⅲ Web relating to function reconstruction, server virtualization, function publishing, and system regulation and optimization are elaborated. Practical operation and tests show that the proposed scheme can satisfy the practical requirements, and improve the performance of the zone Ⅲ Web and the effectiveness of operation, maintenance and management.

Frequency stability will become the main security risk of Yunnan Power Grid as multi-DC sending end with small load and large sending-power after the asynchronous interconnection with CSG. The influences of load model and governor parameters on frequency characteristics are investgated. The principle of coordination and optimization of over-requency generator tripping are proposed. Based on the simulation and analysis of 4 alternative schemes, the over-frequency generator tripping scheme is proposed for Yunnan Power Grid to meet the requirements of asynchronous interconnection.

The lightning strike is an important influencing factor to the operation of China Southern Power Grid (CSG), the lightning location system is one of the effective means to research lightning pattern and guide the lightning protection of power transmission and transforming equipment.CSG Lightning Location System Interconnection System is introduced with the necessity of interconnection, structure, site optimization, application systems, and with the applications in lightning fault point searching, transmission and transforming equipment fault analysis and lightning pattern research.The lightning detection data of the five southern provinces are interconnected. A lightning information WEB application system and a lightning parametric statistical analysis expert system are developed to serve the whole CSG. The entire network probing station locations are optimized on the basis of the whole network probing station distribution and the lightning detection precision requirements. Thus the coverage of lighting location deviation less than 1 km in Guangdong, Guangxi and Yunnan province is improved by 14.9%,1.6%, and 10.3% respectively.The system has been accumulated massive lightning activity data within CSG region since it was put into operation, and can provide guidance to the transmission and transforming equipment lightning fault analysis, the lightning activity pattern research, and the transmission line differentiation lightning protection.

A total of 87 test items has been completed in the system commissioning of Nan'ao VSC-MTDC Demonstration Project.The power step tests show that the system is sensitive to the reactive or active power step.The active power inversion test, wind power grid test and operation mode changeover test show that Nan'ao project can operate steady in all kinds of system conditions.The wind power LVRT test shows that the project has strong fault ride-through capability on AC grid failure.The DC system fault test shows that DC protections at each station have tripped correctly, their control and protection functions are proper.It is verified by the commissioning that the related primary equipment and secondary equipment can completely meet the design requirment, and the engineering functions and performance of the equipment are in agreement with the design specification.

The quality of the power system state estimation and the practical level of advanced power application softwares would be reduced by the wrong parameter.It is very important to ensure the effectiveness of results of the state estimation when multi bad remote sensing data and parameter errors exist.A diagnosis method for the doubtful parameters of the power grid is proposed.The parameter errors and measurement errors are uniformly modeled in the information space.The measured percentage residuals are calculated according to the weighted least square method, and the suspicious measuring point set is obtained by comparison with the threshold.The relevant indexes of all suspicious measuring points and branches are calculated, then Newton Downhill Method is introduced to determine the optimal estimation of each suspicious parameter according to all suspicious branches, and the corrected parameters are regarded as the returned values.Simulation results show that the network parameter errors and measurement data errors can comprehensively be considered through the proposed method, which can also be applied to the situation where there exist multi error parameters simultaneously, and the accuracy of the parameter identification and diagnosis is effectively improved, and the quality of basic operating data and the practical level of advanced applications of the power grid are improved.

According to the demand of ice-melting and dynamic reactive power compensation of power grid, a new design scheme for ice-melting device of MMC based on hybrid sub-module is proposed in this paper, in which half-bridge and full-bridge sub-modules arecoordinated. Then, the method of calculating the number of half-bridge and full-bridge sub-modules is introduced for continuously adjusting the DC voltage of ice-melting device, and it can save up to 1/6 power switches compared with full-bridge MMC, and a capacitor voltage balancing strategy for hybrid sub-modules is also proposed. Finally, the simulation model is validated by PSCAD/EMTDC software, the simulation results verify the correctness and validity of the proposed topology and control method.

With the increase of peak-valley load difference and the integration of large-scale intermittent energy, dispatching merely on power supply may not meet the requirement of system peak regulation, and source-load coordinated dispatch is a feasible solution. This article sets up a source-load coordinated dispatch model based on conventional dispatch models including wind, hydro, thermal and gas power. The model considers the upper and lower constraints and the power consumption constraints of schedulable load, and can be solved by the interior point method. The cases show that the proposed method can improve the accomodation capability of new energy sources.

On April 28th, 2025 Power systems in Spain and Portugal suffered stability destruction and massive blackout. The total power outage duration exceeded 18 hours, affecting the power supply for over 50 million people. The power system overview for Spain and Portugal, including the generation, power network and load profiles, are firstly introduced in this paper. Then, the entire development process of failure and blackout are presented based on the blackout investigation reports provided by the Spanish government and the Spanish power system operator, covering the system operation status before the fault, the failure progression, and the system restoration phases, and the causes of the blackout are summarized. Finally, based on the actual situation of power systems of China, suggestions are proposed for preventing large-scale power outages in the context of high penetration of renewable energy.