Meta-aramid (PMIA) is a unique fiber that possesses exceptional insulation strength and thermodynamic stability. It is widely regarded as an ideal material for the development of the next generation of insulation paper. However, its intrinsic thermal conductivity of 0.21 W/(m·K) is relatively low and may not meet the long-term service requirements in high-temperature environments. To enhance the thermal conductivity and insulation of the PMIA paper, AlN and BN fillers are selected for composite doping modification of PMIA paper. The surfaces of the two fillers are coated with polydopamine (PDA) and modified with a KH550 silane coupling agent to improve the dispersibility of the two fillers. By adjusting the doping ratio, AlN-BN/PMIA composite insulation paper with different concentrations was prepared. The microstructure was characterized and the breakdown strength, conductivity, and thermal conductivity were tested. The effect of two different filler ratios on the insulation and thermal conductivity of the material was studied.

Firstly, the surfaces of the two fillers are coated with polydopamine (PDA) and modified with a KH550 silane coupling agent to enhance their dispersibility. By adjusting the doping ratio, AlN-BN/PMIA composite insulation paper with different concentrations is prepared. Secondly, the microstructure of samples is characterized and the breakdown voltage, conductivity, and thermal conductivity are tested. The influence of the ratio of two fillers on the insulation and thermal conductivity of the material was studied. Thirdly, based on density functional theory, band structure calculation and analysis are conducted, and a design concept of a “stepped charge trap” is proposed. In addition, the composite breakdown model is constructed using the phase field method, explaining the inherent mechanism of performance improvement.

According to the test results, adding BN to the AlN filler can further improve the matrix structure and fix the damage caused by the high concentration aggregation of AlN. The surface of the composite material appears relatively dense when the AlN/BN ratio is 3:7, with only a small amount of PMIA fibers and fillers precipitated. At a mass fraction of 40%, the breakdown strength of the composite gradually increases as the BN doping ratio increases. At a ratio of AlN/BN of 3:7, the composite paper exhibits its maximum breakdown strength of 186 kV/mm, which is 66.07% higher than that of the pure PMIA sample. Additionally, the conductivity of the composite is at its lowest value during this ratio. On the other hand, at an AlN/BN ratio of 7:3, the thermal conductivity of the composite is optimal, increasing by 213.6% compared to pure PMIA samples. The high aspect ratio structure of BN links it with AlN fillers to form an “thermal conductivity network”, which increases the thermal conductivity.

Energy band structure analysis based on density functional theory suggests that the wide bandgap properties of AlN and BN result in the formation of “stepped traps” at the PMIA interface. This leads to an increased energy barrier for charge transitions and limits the migration of charge carriers. In addition, a phase field simulation model indicates that the introduction of BN can further homogenize the electric field distribution, reduce the degree of local polarization, and thus enhance the insulation performance of the composite system.

With a high proportion of power electronic devices connected to the power system, the new power system presents low inertia, low impedance, weak stability and other characteristics, and the risk of operational security increases. In this regard, the grid-forming energy storage converter should be emerged, the grid-forming energy storage converter gives inner loop voltage control the amplitude and phase angle through the power external loop control, presenting the voltage source characteristics. It has active anti-interference, active support characteristics, can effectively solve the problems faced by the new power systems. However, when the system is disturbed and the voltage falls to different degrees, the grid-forming energy storage is limited by the power angle curve of the power outer loop and the fixed active and reactive reference values, which will result in a large power angle instability and a disturbance current of more than 5 times. It threats the security and stability of the system operation. To address this problem, this paper firstly establishes a model of grid-forming energy storage converter. Based on the established model, the droop control power angle curve is plotted, and the transient destabilization mechanism of the grid-forming energy storage converter is analyzed under large disturbances. After analyzing the system, it is known that the stability of the system during large disturbances depends on the existence of an intersection between the system power angle curve and the active power reference value. At the same time, the size of the system disturbance current is affected by the degree of power angle change to a certain extent. Secondly, the disturbance current characteristics and its determining factors are analyzed, and the effect of direct current limiting control on the transient stability of the system is revealed. The analysis results show that the direct current limiting control tends to destabilize the system and cannot be directly used to limit the disturbance current. After theoretical analysis in this paper, it is found that the disturbance current size of the system is positively correlated with the difference between the converter out put voltage and the grid-side voltage, and the converter out put voltage size is correlated with the reference value of the power outer loop reactive power of the structural network type control. Therefore, during the disturbance period, the disturbance current can be limited by adjusting the system reactive power and then controlling the converter out put voltage. Based on the above theoretical analysis, an adaptive low-voltage ride-through (LVRT) control strategy for grid-forming energy storage converter is proposed, which can adjust the active and reactive reference values according to the degree of system perturbation, without switching the control strategy and changing the structure of the grid-forming control strategy. The energy storage converter still exhibits the characteristics of the voltage source during the distribution period, and it has the ability of active support for the system. It realizes effective limitation of the distribution current in the course of maintaining the stability of the system. At the same time, the disturbance current is effectively limited. Finally, the effectiveness of the proposed control strategy is verified by simulation and semi-physical experiment.

Dry-type transformer is to high voltage level, high power density direction, long-term operation in the electro-thermal cooperative multi-stress complex working conditions such as epoxy resin casting insulation is more likely to induce along the surface flashover failure. In order to study the characteristics of epoxy resin along the surface flashover under the stress of electro-thermal cooperative aging, this paper builds a platform for flashover along the surface under AC stress, and it is found that when the aging temperature is 160℃, the flashover field strength of the epoxy resin specimen aged for 80 days is 2.11 kV/mm, which is a decrease of 25.7%. The steepest decrease in the field strength along the surface is found from 0 to 40 days, which is related to the rapid increase in the surface roughness of the specimen from 0 to 40 days.
A plasma model of epoxy resin flashover along the surface is established by combining the continuity equation of charged particles, the average electron energy equation and the interfacial reaction characterization equation, and the dynamic simulation of flashover along the surface at the working frequency is realized. According to the results of the aging experiment, a random function is introduced to change the surface roughness of the medium, and the dielectric constant after aging is combined to simulate the accurate electro-thermal aging behavior of the epoxy resin, and the temporal and spatial evolution laws of the tangential electric field strength, electron density and surface charge density of the epoxy resin in the process of flashover before and after aging are obtained. The simulation results show that the electron density and surface charge density increase during the flashover development of the aging epoxy resin, and the electric field strength at the head of the flow injection reaches 1.183 kV/mm at 12 ns, an increase of nearly 10.87%. With the aging specimen due to the roughness and dielectric constant increase, its surface charge density will occur surge phenomenon, compared with the aging specimen before the increase of 57.66%, so that the electron density quickly reached the threshold value of the electron collapse to flow injection, resulting in the development of the flashover becomes faster.
The mechanism of combined electro-thermal aging on the surface charge of epoxy resin specimens is explained by the trap effect, and the reason for the decrease in the flash field strength of the specimens is clarified. For the specimen aged for 80 days, the deep trap density and energy level increase to 2.56×10¹⁶ eV^-1·m^-3 and 1.06 eV, respectively, resulting in an increase in the probability of charge entry trapping, which leads to a large amount of surface charge accumulation, and the electric field distortion becomes more serious, thus decreasing the flash-coincidence field strength along the surface. The above findings provide theoretical and methodological basis for the fault operation and maintenance and life prediction of dry-type transformers.

Metallic foreign objects in various types of power equipment may cause discharge problems. To achieve accurate multi-spectral monitoring of the discharge phenomenon caused by metallic foreign object, it is necessary to deeply understand its influence on the mechanism of optical radiation during discharge. Currently, research on the impact of metallic foreign objects on high-voltage discharge is mostly focused on the macro level, without delving into the micro-particle level to analyze its effect on the discharge mechanism, and the influence of metallic foreign object on optical radiation during discharge has not been thoroughly explored. To address these issues, this paper analyzes the characteristics of metallic foreign object's impact on the full-band optical radiation of discharge and its influence mechanism on the day-blind ultraviolet band through experiments and simulations.
A high-voltage discharge experimental platform was first constructed. Discharge images were captured using ultraviolet and high-speed cameras, and the emission spectra were measured with a spectrometer to investigate the influence of metallic foreign object on full-band optical radiation during discharge. The effect of metallic foreign objects on the generation of day-blind ultraviolet radiation was further studied. It was verified that the particle transitions responsible for producing day-blind ultraviolet radiation are mainly $\mathrm{N}_{2}\left(\mathrm{~A}^{3} \Sigma_{\mathrm{u}}^{+} \rightarrow \mathrm{X}^{1} \Sigma_{\mathrm{g}}^{+}\right)$ and NO-γ(A²Σ⁺(v′)→X²Π(v″)). Based on this, a two-dimensional plasma simulation model was constructed to investigate the effect of different quantities of large metallic particles and varying masses of metal shavings on the discharge process. The model was used to calculate the number densities of NO(A²Σ⁺) and $\mathrm{N}_{2}\left(\mathrm{~A}^{3} \Sigma_{\mathrm{u}}^{+}\right)$ particles under different conditions, and the simulation results were validated by comparing them with the measured spectra. The experimental and simulation results were then comprehensively analyzed to explore the influence of metallic foreign object on day-blind ultraviolet radiation during discharge.
High-speed camera reveals that metallic foreign object increases the chance of arc formation between the tip of the needle electrode and the metallic foreign object. From the spectrum of the 200-1000 nm band measured in the experiment, it is evident that the increase in metallic foreign object enhances the optical radiation across the entire spectrum generated by the discharge. However, this enhancement is selective to certain bands, with the ultraviolet and visible light bands responding more sensitively. Therefore, ultraviolet and visible light detection is more effective for monitoring discharges caused by metallic foreign objects.
Analysis of UV images, 240~280 nm spectra, and simulations shows that an increase in the metal foreign object causes an increase in the amplitude of the spectral curve of the sun-blind UV band, an increase in the number densities of NO(A²Σ⁺) and $\mathrm{N}_{2}\left(\mathrm{~A}^{3} \Sigma_{\mathrm{u}}^{+}\right)$ particles, and an increase in the rate of the chemical reactions in the discharge region; however, the spectral shape remains basically unchanged, which means that it does not affect the types of chemical reactions and the relative ratios among them. By combining the electric field simulation results, the reason can be analyzed as follows: the metal foreign object increases the strength and inhomogeneity of the electric field, promoting the excitation and ionization of particles. This leads to the production of more NO(A²Σ⁺) and $\mathrm{N}_{2}\left(\mathrm{~A}^{3} \Sigma_{\mathrm{u}}^{+}\right)$ particles, thus promoting the enhancement of the sun-blind ultraviolet radiation.
The results of this paper apply to discharge phenomena in air influenced by metallic foreign objects, and the influence of metal particles on discharge in SF₆ and its alternative gases will be further investigated in the future.

As electric vehicles (EV) grow more popular and vehicle-to-grid (V2G) technology advances, large-scale EV aggregations (EVA) have become integral to the power system. However, effectively capturing the distinct idle energy storage characteristics of EVAs across regions and integrating them seamlessly into power system operations remains a challenge. The shortcomings of existing research can be summarized as the follows: Firstly, current methods for assessing the dispatchable regions (DR) of EVs remain inadequate, lacking systematic frameworks and classification methods. Secondly, current multi-level coordinated control strategy often overlooks the holistic nature of coordinated control, which spans multiple levels, including the power grid, garage, and users. Merely considering factors related to EVs and their users is insufficient, as it fails to provide a comprehensive guidance for all coordinated control participants, such as the power grid and garage.
This paper addresses the aforementioned issues by conducting the following works. Firstly, methods for establishing multi-stage electric vehicle dispatchable region (MEVDR) for both EV and EVA are proposed and further investigated. Secondly, the probability density functions of various EV data in different regions and time periods of clustering centers are captured using Gaussian mixture model (GMM). Thirdly, the MEVDR of EVAs in different regions and time periods are established and comprehensively analyzed. Furthermore, the proposed MEVDR model can be used to construct multi-period constraints. Based on this, a vehicles-garage-grid multi-level coordinated control system (VGGMCCS) based on MEVDR can be constructed, which consists of two levels and can therefore be considered a bi-level model. After a thorough analysis, VGGMCCS incorporates two mixed integer programming (MIP) problems, allowing the use of commercial solvers for rapid and efficient problem solving. Finally, in order to provide further validation of the effectiveness of the VGGMCC system based on MEVDR, a comparison was made between the proposed method and the contrasting strategies.
The case study shows that, when compared to two contrasting strategies, the proposed VGGMCCS has been demonstrated to reduce the grid network loss by 12.17% compared to comparative strategy 1 and by 8.69% compared to comparative strategy 2 during peak electricity demand periods. And to reduce users′ average daily charging costs by 7.88% compared to comparative strategy 1, and to increase operators′ revenues by 17.63% compared to comparative strategy 2. Meanwhile, the load fluctuation amplitude of the transformer at the garage node has been significantly reduced. During peak electricity consumption periods, the power fluctuation of transformers under VGGMCCS decreased by 96.36% compared to comparative strategy 1 and by 82.59% compared to comparative strategy 2. Last but not least, VGGMCCS also has a high solution speed, ensuring decision accuracy while quickly responding to dispatching requests from lower-level garages, effectively reducing both the time and economic losses caused by rescheduling requests after EVs are integrated into the power grid. The results show that VGGMCCS can effectively reduce users′ costs, improve the economic benefits of the garage and enhance the operational efficiency of the power grid, while ensuring the long-term stable operation of the power system, thus achieving a win-win situation for users, garage operators and power grid companies.
In summary, this paper provides a thorough establishment and analysis of EVA′s MEVDR across a diverse range of geographical and temporal contexts. Furthermore, when compared to the contrasting strategies, the proposed VGGMCCS promises to enhance both the economic benefits and operational efficiency of the power system significantly.

In China, the current renewable energy resources mainly use grid-following converters as grid-connected interfaces, which cannot provide inertia and damping support for power systems. In order to enhance the support capacity of renewable energy resources, grid-forming inverters are emerging as a promising solution as they can emulate the dynamic property of synchronous generator and provide support. However, the grid-forming inverter faces significant risks of transient synchronous instability. Current research primarily focuses on single grid-forming inverter systems, which cannot be applied to multi-machine systems due to complex interactions between converters. Quantitative transient analysis and the method of stability region estimation for multiple paralleled grid-forming inverter systems are absent.

To fill this gap, taking transient interaction and power coupling into consideration, the large-signal equivalent model of multiple grid-forming inverters system is established. Based on this model, a set of Lyapunov functions is constructed, which accounts for damping dissipation, reactive power loop dynamics, and transient interactions, enabling intuitively and accurately plotting the stability region for multi-machine system. Then, by comparing the sizes of the stability regions, the impact of control parameters and grid parameters on the stability boundaries of grid-forming multi-machine systems is quantified. Furthermore, the influence of damping dissipation, reactive power loop dynamics, and transient interactions on the transient stability margin is explored. Finally, hardware-in-the-loop experiments validate the accuracy of the estimated maximum stability region.

The following conclusions can be drawn from the analysis in this paper: (1) Due to the complex interaction, the equivalence model and transient characteristics of multi-machine system are more complex than those of single-machine system. (2) The Lyapunov function set, which takes into account voltage dynamics, damping dissipation and transient interaction, can accurately estimate the maximum stability region of multiple grid-forming inverter systems, and predict the transient synchronization stability via the location of the fault clearing point. (3) By comparing the size of the stability region, the increase of reference power, fault depth, and line impedance will reduce the stability region, and the increase of damping coefficient, inertia, and reactive droop coefficient will enlarge the stability region. The voltage dynamics and damping dissipation can increase the stability margin of the system, and the transient interaction between units can reduce the stability margin.

The oil-filled terminal adopts a solid-liquid composite insulation composite structure composed of silicone rubber (SiR) stress cone and silicone oil (SO) inside. Compared to the cable body, when the composite insulation interface is invaded by moisture or contains air gaps or impurities, it can cause electric field distortion. This distortion can trigger creepage and even flashover along the surface of the stress cone, significantly impacting the service life of the oil-filled terminal. Among them, moisture intrusion is recognized as the main factor causing insulation deterioration in cable terminals, and cable termination failure rate caused by it account for about 50%. Therefore, the moisture migration process and equilibrium characteristics between SO and SiR solid-liquid medium in the oil-filling terminal need to be further studied. In this paper, the moisture migration law between SO-SiR composite insulation system in oil-filled terminals is systematically studied, the swelling model and mechanism of SO in the terminals are discussed, and the moisture equilibrium characteristics of SO-SiR composite insulation systems under the effect of temperature and swelling are clarified.
Firstly, this study conducted moisture absorption experiments on SO and SiR under various temperature and humidity conditions. The water content of SO and SiR at different temperature and humidity equilibrium states was measured. Using the indirect equilibrium theory, a moisture equilibrium curve for the SO-SiR composite insulation was plotted. The results show that the water content of SO has a linear relationship with the relative humidity at the same temperature, and the saturated water content of SO changes exponentially with temperature. The water content of SiR has a nonlinear relationship with relative humidity, and the saturated water content of SiR does not change with temperature. As the temperature rises, moisture migrates from the SiR to the SO.
In addition to the moisture migration between the SO and the SiR duplex medium in the oil-filled terminal, the SO will also diffuse into the SiR. This diffusion destroys the physical and chemical cross-linking results of the SiR, and affects the moisture absorption characteristics of the SiR. Therefore, it is necessary to clarify the physical mechanism underlying the swelling of SiR by SO. The results show that the SO swells into the SiR in the form of free state and bound state according to the Langmuir diffusion process. With increasing time, the swelling rate increases as a logarithmic function. With increasing temperature, the equilibrium swelling mass remained unchanged, but the swelling rate increased. Under the SO (solvent)-SiR (solute) system, the elastic free energy of the system increased due to the swelling of SO, which was offset by the Gibbs free energy. Finally, the total free energy is zero, and the swelling reaches equilibrium.
On this basis, the moisture equilibrium curve of SO-SiR composite insulation was further optimized. After the swelling of SO, the free volume of SiR increases, which can dissolve more water. However, SiR with different degrees of swelling still exhibits the same water absorption characteristics as unswollen SiR. Combined with the moisture dissolution characteristics of SO, the moisture equilibrium surface diagram of SO-SiR composite insulation under temperature and swelling was drawn. With increased swelling, water molecules migrate from the SO to the SiR. Through this surface diagram, the water content of SO and SiR under different equilibrium states can be obtained, and the operation and maintenance of oil-filled terminals can be guided.

In recent years, with the in-depth reform of the electricity market and the continuous improvement of the penetration rate of distributed resources in the distribution network, the energy trading between intelligent buildings with dual attributes of production and consumption has brought new opportunities and challenges to the nearby consumption of distributed energy. However, for the microgrid system with multi-intelligent buildings, there are defects such as large amount of communication information, low robustness and user privacy in the process of power trading. At the same time, it will also be affected by various uncertain factors such as the access of new energy and the lack of timeliness of transactions. In order to solve the above problems, this paper proposes a rolling P2P energy trading optimization strategy based on distributed information interaction for multi-intelligent buildings in microgrid.
Firstly, considering the aggregation characteristics of various flexible resources in intelligent buildings, the prediction interval results of distributed photovoltaic power generation and the feasible range of flexible resources are characterized in the form of aggregation power interval by Minkowski summation theory, and the aggregation interval model of P2P transaction is established. Among them, the distributed photovoltaic prediction interval is modeled by transforming the benchmark output at different confidence levels into the prediction quantile for the feasible region. At the same time, an interval rolling P2P energy trading framework is constructed. During the energy management period, each building participates in the rolling P2P energy trading by combining the aggregated power interval with its own electricity purchase and sale strategy. Secondly, the risk cost brought by the uncertainty of photovoltaic output to P2P transactions is quantified by CVaR, and an economic dispatch model with the minimum total operating cost of microgrid multi-intelligent buildings is established. On this basis, the P2P transaction power between buildings is used as a consistency variable, and the P2P transaction power and transaction price are obtained based on the distributed solution of the information interaction between adjacent buildings, and the energy transaction period is continuously pushed backward until it meets the requirements of all intelligent buildings in the microgrid.
In the case analysis, the scheduling results of different buildings in the microgrid and the optimization results of different algorithms are compared respectively, which verifies the effectiveness of the interval rolling P2P energy trading model proposed in this paper. At the same time, the practicability and solution efficiency of the distributed information interaction algorithm in this paper have also been reflected. Through the example analysis, the following conclusions can be drawn: (1) Participating in the energy transaction between buildings in the form of aggregation interval fully taps the scheduling potential of flexible resources in buildings and improves the flexibility of coordinated scheduling of multi-intelligent buildings in microgrid. (2) Compared with the ordinary P2P trading, the rolling P2P energy trading improves the enthusiasm of intelligent buildings to participate in energy trading and the self-consumption level of distributed energy while taking into account the economy of system operation. (3) The distributed information interaction strategy proposed in this paper makes the multi-intelligent buildings in the microgrid only need to interact with the expected transaction volume information, and at the same time solve their own optimization problems in parallel, which has a good fit with the rolling P2P transaction mode. It avoids the problems of high computational pressure and privacy leakage, and improves the convergence speed of distributed information interaction. It has good scalability and can effectively solve the optimization iteration problem of large-scale intelligent buildings.

Ice disasters can cause serious damage to power transmission network, it is crucial to enhance the resilience of power transmission network during ice disasters. Unlike extreme natural disasters such as hurricanes or earthquakes, ice disasters develop slowly and last long time. It is difficult to predict the development trend of ice disaster accurately due to the influence of microclimate and terrain on their geographic coverage. Currently, the spatiotemporal evolution patterns of ice disasters are not clear. The existing research on improving the resilience of power transmission networks considering the impact of ice disasters have not involved the temporal modeling of ice disaster scenarios. Therefore, the paper proposes a method for temporal modeling of ice storm scenarios based on multispectral satellite remote sensing. By combining multispectral remote sensing image fusion methods based on Laplacian pyramid decomposition, efficient extraction and analysis of the spatial distribution and temporal changes of ice-covered areas in Sentinel-2 satellite remote sensing images are achieved. Using partial differential convolution, ice-covered areas are predicted dynamically based on the fused images, and an ice disaster temporal model is constructed. Additionally, a conditional variational autoencoder is used to generate a set of ice disaster scenarios, which accurately reflect the spatiotemporal characteristics of "source-network-load" during ice disasters.
Considering the interaction between the disaster development process and resilience enhancement measures, the power transmission system resilience can be simultaneously enhanced through both pre-disaster prevention and in-disaster repair measures. This paper proposes a comprehensive resilience evaluation index and constructs a two-stage robust resilience enhancement planning model for power transmission networks based on the set of ice disaster scenarios. The first stage focuses on pre-disaster fixed energy storage configuration and pre-planning of maintenance resources to find the optimal investment decision. The second stage focuses on in-disaster power supply through fixed energy storage and emergency maintenance considering limited maintenance resources, ensuring rapid response from fixed energy storage and maintenance teams after the occurrence time of the ice disaster, which aims to ensure rapid load recovery, maximize system resilience, and minimize system economic losses. The model is iteratively solved using a parallelizable column-and-constraint generation algorithm.
Finally, case studies are conducted using ice-covered remote sensing data from a region in Yunnan and a modified IEEE RTS-79 power transmission system as the test system. The results show that the coordination of fixed energy storage power supply and emergency maintenance can effectively ensure power supply and transmission during ice disasters, as the system resilience improved by 90.97% and total system losses decreased by 43.19% during the ice disasters. Compared with other resilience enhancement strategies, the proposed strategy in this paper balances both economic efficiency and resilience. What’s more, different ice disaster center locations are set in the case study considering the inherent uncertainty of ice disasters. The results demonstrate that for ice disasters with multiple origins, the proposed method effectively ensures power restoration in the transmission system, enhances system resilience, reduces load shedding losses and total costs.

After the high proportion of wind power is connected, it brings a series of problems to the stability of the frequency and voltage, and the grid needs wind power to assume the main responsibility for ensuring power supply. Existing studies have shown that the virtual synchronous grid-forming equipment, including grid-forming wind turbines, has good frequency/voltage active temporary and steady-state support capabilities, and has better temporary and steady-state adaptability in weak grid scenarios. Based on these advantages, grid-forming wind turbines are expected to play a greater role in the future grid supported by low inertia and weak voltage. However, the maximum power point tracking (MPPT) operation mode of the wind turbine and its own limited rotational energy lead to the restriction of the transient support capacity of the grid-forming permanent magnet synchronous motor(PMSG), while the grid-forming PMSG based wind-storage generator has an additional energy source due to its access to energy storage, and its transient support performance has been greatly improved, which is an effective solution. At present, the access mode of energy storage is mostly parallel energy storage on the DC side or AC side, in which the energy storage driven by grid-following control adopts the passive mode of responding to the frequency acquisition signal to support the grid frequency, and most of the energy storage driven by virtual synchronous grid-forming control is connected to the AC side of the wind turbine, and the energy storage cannot be incorporated into the virtual synchronous control system. Therefore, this study is dedicated to proposing a transient support capacity improvement strategy for grid-forming PMSG based on wind-storage integration.

Firstly, the power energy storage represented by the supercapacitor was selected to form a grid-forming PMSG based Wind-storage generator with grid-forming PMSG, and the dynamic model of the grid-forming PMSG and grid-forming PMSG based wind-storage generator were established, and the constraints of the wind turbine dynamics on the frequency support capacity and transient stability of the grid-forming PMSG were summarized by analyzing the transient response of the grid-forming PMSG under frequency and voltage drops.

Then, combined with the energy flow characteristics of the grid-forming PMSG based wind-storage generator in the transient support process, the transient response power of the Grid-forming control is decomposed into inertia response power signal and damping response power signal to drive energy storage, and a transient support capacity improvement strategy for grid-forming PMSG based on wind-storage integration is formed, which realizes the flexible allocation and invocation of rotor kinetic energy and energy storage, and incorporates the rotor kinetic energy and energy storage into the active support system of virtual synchronous control to improve the frequency support capacity and transient stability of the grid-forming PMSG based wind-storage generator.

Finally, after simulation verification under various conditions, the strategy can improve the transient support capacity of the grid-forming PMSG based wind-storage generator, including: (1) The frequency support capacity has been improved, which reduces the constraints of MPPT on the frequency support capacity of the wind turbine. (2) The fault ride-through capability is improved, the transient fluctuation of rotor speed and DC bus voltage is effectively suppressed, the redundant energy generated by fault ride-through is effectively absorbed. (3) Combined with the fault ride-through power angle stability control strategy, the redundant energy during the fault period is converted into energy storage energy, so as to avoid the reduction of wind turbine power generation efficiency and reduce energy waste.