PV systems are typically equipped with reactive power compensation devices when connected to the grid, and static synchronous compensator (STATCOM) devices are widely employed due to their flexible control capabilities. The increasing utilization of power electronic devices in the power grid has resulted in a shift from physical synchronization to control synchronization as the dominant mode of system operation. Analyzing static synchronization stability problem is more challenging for these systems compared to conventional power systems, as converter output characteristics are influenced by control strategies. Therefore, it is imperative to urgently address the problem of static synchronization stabilization under control strategy dominance.

First, this paper establishes the static synchronous stability analysis model of the grid-connected converter based on the control loop and circuit structure of each converter in a parallel system under the respective dq reference frame. The dq reference frame of the converter is determined by the phase information provided by the control loop in a multiple converter parallel system, thus enabling a unified coordinate system for static synchronization stability analysis. Subsequently, an equivalent small signal model is developed for analyzing multiple grid-connected converters. In comparison with existing coordinate conversion methods, Kirchhoff's current law is incorporated to enhance accuracy and reduce errors.

Then, the stability criterion for impedance analysis is enhance, and the static grid-synchronization performance indices are created. The small perturbation oscillation characteristics are measured using overshooting and regulation time, while the participation factor is employed to analyze the impact of each pole of the system. Finally, the attenuation coefficient is utilized to assess static synchronization stability performance.

The model is developed in Matlab/Simulink for simulation verification. Subsequently, an analysis is conducted on the impact of parameters such as the control loop parameters and STATCOM capacity on static synchronization stability. The main conclusions are summarized as follows:

(1) Optimizing the reactive power output of the grid-connected converter based on known control parameters can significantly enhance static synchronization stability performance, with the dominant influence of small perturbations after oscillation mode being attributed to poles generated by phase-locked loop control.

(2) The attenuation coefficient of the system exhibits a rapid increase in proximity to the critical stability region. Hence, it is imperative for the system to possess a certain margin of attenuation coefficient during operation. Based on the simulation analysis results presented in this study, static synchronous instability phenomena occur when the attenuation coefficient of the PV system exceeds 300. Conversely, when the attenuation coefficient falls below 250, the system remains in a state of static synchronous stability. These findings establish a criterion for analyzing and assessing static synchronization stability within such systems.

(3) The addition of STATCOM to the PV system primarily impacts the conductance matrix transfer function of the q-coupled channel. The phase-locked-loop coupling oscillations between the grid-connected converters do not affect the dd channel. Within the stable operating region, an increase in bandwidth for the DC voltage control loop, active current control loop, and reactive current control loop results in an amplification of both attenuation coefficient and system oscillation amplitude.

(4) When the phase-locked loop parameters of the STATCOM are the same as the PV system, the stability performance of the system is mainly affected by the grid impedance and the equivalent conductance transfer function of each grid-connected converter. And each grid-connected converter can independently connect to the grid and achieve stable operation to ensure that the system achieves static synchronous stability in this case.

(5) In cases where the active output of the PV system is low, STATCOM typically adjusts its capacitive or inductive reactive power provision to improve static synchronization stability performance. Conversely, when compensating for capacitive reactive power, utilizing STATCOM may yield superior results compared to using the PV grid-connected converter alone. Hence, allocating an optimal capacity for STATCOM can significantly enhance static synchronization stability performance.

As the penetration rate of renewable energy resources continues to increase, the traditional power system based on synchronous generators is evolving into a power system based on diversified power electronic equipment. The small disturbance stability analysis problem of multi-converter grid-connected system has attracted widespread attention. State-space model and impedance-based model are two main small disturbance stability analysis methods. Being as the white-box method, state-space model can be difficult to apply in practice because the differential equations describing the controllers of converters are not generally openly available due to commercial confidentiality. Impedance models have been popular in the field of power electronics for analysis of interactions between grid and converters. However, applying it directly to the stability analysis of multi-converter system will make the analysis process very complicated. Generally, the existing state-space and the impedance method still have room for improvement for the small disturbance stability analysis and sensitivity analysis of the oscillation mode of each converter.

Firstly, this paper proposes a single-input single-output (SISO) dq impedance stability criterion for analyzing the small disturbance stability of the multi-converter grid-connected system. Secondly, based on the formula of the stability criterion proposed, an expression for calculating the closed-loop pole of the system is derived. Because this formula is only a scalar function, the accuracy can be guaranteed for the usage of vector fitting (VF) method. Furthermore, a method for analyzing the sensitivity of oscillation modes to the impedance/admittance of each converter is proposed. This method can effectively evaluate the influence of different converters on the oscillation modes and help identify the dominant converter that causes oscillations. Finally, the accuracy of the proposed method is verified by Matlab/Simulink simulation and hardware-in-the-loop experiment.

The results are as follows: firstly, the proposed multi-converter system model can be used to represent the converter grid-connected system with any network structure and any number of grid-forming and grid-following converters. Based on the proposed method, it can be used to analyze the overall stability of the system as well as the influence of each converter on the system stability. Secondly, the proposed sensitivity analysis method can be used for evaluating which power converters are more sensitive to the close-loop poles and have a significant contribution to the harmonic instability.

The following conclusions can be drawn from the above results: (1) A recursive stability evaluation method for analyzing the stability of the multi-converter grid-connected system based on SISO dq impedance ratio is achieved, and a complete stability evaluation procedure is provided. Compared with the stability analysis method based on generalized Nyquist criterion, the stability analysis problem of a MIMO system is transformed into the stability analysis of a series of SISO systems, and the stability analysis of the whole system can be realized only by the impedance ratio of d-axis and q-axis in the stability analysis process. Because the SISO impedance ratio is used for stability analysis, the solution of the eigenvalues of the high-order return rate matrix required by the traditional method can be avoided, and the complexity of Nyquist plot analysis required for MIMO system can be effectively reduced. (2) In the proposed impedance stability criterion, dq impedance is adopted to model the VCI while dq admittance is used to describe the CCI, so the complicated procedure for obtaining the RHP open loop poles can be avoided. (3) Based on the proposed stability criterion proposed, an expression for calculating the closed-loop pole of the system is derived. Since this paper adopts dq coordinate system for modeling and derivation, compared with the sequential impedance model, the transfer function matrix elements can be guaranteed to be rational fractions, so the closed-loop poles can be obtained by VF method. (4) The sensitivity formula of the system's closed-loop poles on the dq admittance/impedance of the converter in the system is derived in this paper. Combining with the residual of the closed-loop poles obtained by the VF method, it can be used to analyze the influence of each converter on the key modes in the system. Therefore, it is helpful to identify the source that causes oscillatory instability.

Hydrogen, as a clean, efficient, and high-quality energy source, is recognized as a crucial solution for decarbonizing the energy system and mitigating climate change. The electricity and hydrogen energy system, which uses electricity and hydrogen as energy carriers, represents a key pathway for integrating power systems with hydrogen energy. It helps overcome the developmental limitations of renewable energy, fosters the interconnection and complementarity of multiple energy modes, and promotes deep integration across generation, grid, load, and storage. The electro-hydrogen coupling process, central to this system, can lower operating costs through peak shaving and valley filling. However, the efficiency of electrolyzers and fuel cell remain suboptimal, resulting in significant exergy losses alongside economic benefits during the coupling process. Striking a balance between economic viability and energy saving continues to be a challenging task. Moreover, the substantial forecasting errors caused by the uncertainty of renewable energy outputs can negatively impact the supply-demand balance and the operating conditions of electrolyzers. Therefore, the uncertainty risks associated with renewable energy must be thoroughly considered in optimal scheduling. In response to the above problems, a robust optimal scheduling model based on exergoeconomic analysis is proposed, with the uncertainty set defined by the confidence interval to reduce the conservatism of robust optimization.

Firstly, considering the dynamic efficiency characteristics of the electrolyzer, piecewise linearization was applied to handle the non-convex terms introduced by this relationship. The operation model of the electrolyzer including hydrogen production power allocation and operation models of fuel cell and energy storage equipment were constructed. Secondly, the energy quality coefficients were employed to analyze the exergy loss distribution based on the equipment operation model. A cost accounting method for exergy losses, including both internal and external factors, was proposed. Internally, the cost allocation method was used to price unit exergy losses, enabling the calculation of operational loss costs based on the distribution of exergy losses. Externally, the cost of transmission line losses and penalties of wind curtailment were calculated according to current electricity prices and relevant policies. Thirdly, taking into account constraints such as electrolyzer start-stop cycles, ramping power, and energy balance, an optimal scheduling model was developed with the goal of minimizing total exergy loss costs in the electricity and hydrogen energy system. Then, the model was reformulated into a robust optimization problem based on the uncertainty set of the confidence interval，and a dual transformation method for solving the model was proposed.

In the case simulation, four cases are set up for comparative analysis, leading to the following conclusions: (1) By setting the wind curtailment penalty coefficient appropriately, with the goal of minimizing exergy loss costs, a balance can be achieved between the economic benefits and the exergy losses associated with the electricity-hydrogen coupling process, while ensuring the efficient absorption of wind power. (2) The proposed model can further improve the overall hydrogen production efficiency of the electrolyzer array by taking advantage of the flexibility of hydrogen production power allocation. (3) The confidence interval is used as the uncertainty set of robust optimization, which can take into account the probability characteristics of random variables, and reduce the conservative degree of system operation under the premise of ensuring robustness.

Hydrogen energy system, with its inter temporal and spatial transfer characteristics, shows great potential for enhancing the resilience of distribution grids. However, few literatures have considered the inter temporal and spatial flexibility of hydrogen energy system and the inter-regional support capability of mobile emergency resources, and the post-disaster collaborative recovery mechanism of multi-region electric-hydrogen integrated energy system (MR-EH-IES) is still unclear, which makes it difficult to exploit the inter-regional support potential of mobile resilience resources. Aiming at the above problems, this paper proposes a post-disaster recovery strategy for MR-EH-IES with cross-regional resource sharing.

This paper firstly proposes a two-layer MR-EH-IES disaster recovery framework based on the idea of “intra-regional autonomy, resource integration, inter-regional sharing”. In the lower layer, the electric-hydrogen integrated energy system (EH-IES) carries out intra-zone autonomy. The potential of synergistic cooperation between mobile electric energy storage, hydrogen fuel power generation vehicles, maintenance personnel and hydrogen energy system in disaster recovery is fully considered, and the EH-IES disaster recovery model considering the synergistic scheduling of distributed power sources and maintenance personnel is established. At the upper level, the joint disaster resilience center carries out the coordinated allocation of mobile resilience resource (MRR). Starting from the disaster recovery mechanism of different types of MRR, the key factors affecting its allocation are analyzed, the MRR disaster recovery mechanism considering cross-region support is proposed, and the MRR disaster allocation model considering cross-region resource sharing is established. Then, based on the above framework and strategy, the MR-EH-IES two-layer disaster recovery model considering cross-region resource sharing is proposed.

The simulation analysis shows that the total cut-load loss of MR-EH-IES decreases by 22.4% after considering cross-region resource sharing, in which the cut-load loss of region 1 and region 3 increases slightly by ¥1.3×10³ and ¥7.3×10³, respectively, while the cut-load loss of region 2 and region 4 decreases by ¥157.8×10³ and ¥62.5×10³, respectively. Specifically, in the early stage of disaster recovery, when the mobile power supply left from region 1 and region 3 to support region 2 and region 4, the weighted load recovery rate of region 1 and region 3 showed a short drop, with the maximum drop of 0.5% and 1.1%, respectively, but both of them were higher than the weighted proportion of important loads. Meanwhile, the load-weighted recovery rates of region 2 and region 4 increased significantly, with maximum enhancements of 11.0% and 4.2%, respectively. In addition, when region 1 and region 3 were restored, idle mobile power supplies and maintenance personnel were the first to support other regions.

The following conclusions can be drawn from the simulation analysis: (1) The post-disaster recovery strategy proposed in this paper is able to rapidly restore the supply of important loads and reduce the system damage in the early stage of disaster recovery through the reasonable allocation of mobile emergency resources, and improve the utilization rate of mobile emergency resources in the later stage of disaster recovery. (2) The inter temporal and spatial flexibility of the hydrogen system and the long tube trailer can increase the energy transfer channels of MR-EH-IES in time and space scales, giving full play to the ability of hydrogen energy system to support the power grid in disaster recovery.

In recent years, the rapid development of renewable energy has posed a significant challenge to the breaking capacity of DC circuit breakers in power systems. Gas-blowing arc extinguishing technology based on gassing materials can greatly enhance the breaking capacity of DC circuit breakers. However, the macroscopic and microscopic pyrolysis mechanisms of gassing materials are unclear.

Firstly, the micro-pyrolysis mechanism of typical gassing material polyamide 66 (PA66) at different pyrolysis temperatures and rates was analyzed based on the reactive force field (ReaxFF). The decomposition process of PA66 and the types and quantities of small molecule gases produced were discussed. It was found that the initial bond breaking of PA66 occurred in the C—C bond adjacent to the amide group. H₂ and H₂O were the main pyrolysis gases of PA66, and their production process was analyzed. The reaction rate of carbon-free small molecule gas at high temperatures accelerates, and the amount increases. The product amount with carbon atoms below four increases rapidly and decreases slightly after reaching a peak. The main reasons are the Diels-Alder reaction, C3/C4 reaction, and cyclization reaction in the unsaturated hydrocarbons in the product, which leads to the decrease of hydrocarbon molecules. The temperature increase aggravates the disintegration of the PA66 molecular chain and the formation of small molecular gas. The heating rate of the system affects the distribution of heat in the reaction system, thus affecting the formation of the product. The slower the heating rate of the system, the more conducive to the uniform distribution of heat in the reaction system. Additionally, the amount of carbon deposition during pyrolysis at 2 600 K was analyzed. Light tar was dominant, followed by heavy tar, with the least amount of coke.

Subsequently, pyrolysis experiments at four different heating rates were carried out. Based on the Flynn-Wall-Ozawa isoconversional model, the average activation energy of PA66 was 194.85 kJ/mol, which was very close to the activation energy of 195.015 kJ/mol obtained by molecular dynamics simulation. Additionally, the pyrolysis gas distribution of PA66 was analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments, which verified the accuracy and reliability of the pyrolysis kinetics calculation method. PA66 is suitable for the first-order reaction kinetic model, and the simulation data have high accuracy and reliability for the thermal decomposition reaction path and gas type of PA66 at the microscale.

Finally, simulation calculations and arcing experiments of three gas-producing materials, PA6, PA46, and PA66, were carried out. The gas generation rate and quantity changes during pyrolysis were observed, and the transient pressure changes during the arc-breaking experiment were analyzed. The order of transient pressure generated during the arcing process is PA6>PA46>PA66, consistent with the trend of the number of product gas molecules obtained by simulation calculation. The ReaxFF simulation results are confirmed and supplemented with the arc-breaking experiment, further verifying the reliability and accuracy of the research.

This paper offers a theoretical framework for understanding the macroscopic pyrolysis behavior and the microscopic pyrolysis mechanism of gassing materials. It contributes to a deep comprehension of material behavior under high-temperature and arc conditions, laying a methodological foundation for evaluating the performance of gassing materials in DC circuit breakers.

The low-voltage power supply and distribution system is directly connected to the user at the end of the power system. Its wide distribution, diverse applications, and complex structure make overhauling difficult and lack safety maintenance. Due to its negative resistance characteristics, the series arc can decrease line current, exhibiting high concealment of fault characteristics. It is a loophole in traditional relay protection methods. The series arc fault can produce high temperatures in a short time, which can cause a fire very quickly. The temperature characteristics of AC fault arcs have not been thoroughly studied, the development process and influencing factors of fault arc temperature are not apparent, and the mechanism of arc ignition and disaster needs to be clarified. This paper builds a real experimental platform for arc ignition, constructs a numerical simulation model of AC arc fault based on magnetohydrodynamics, verifies the temperature characteristics of arc fault through simulation and experiment, clarifies the ignition mechanism of arc fault, and puts forward suggestions for the improvement of relevant standards.

Firstly, based on the IEC 62606 standard, combined with a temperature acquisition device, an experimental platform for arc fault ignition risk is built to simulate arc faults. The current, voltage, temperature, and thermal imaging images are collected. Secondly, the physical characteristics of AC fault arc and related test standards are analyzed, and a complete set of fault arc simulation schemes is designed. Thirdly, the control equation, calculation domain, and boundary conditions of the arc fault magnetohydrodynamic simulation model are defined, the material parameters are designed, and the division of the simulation grid is refined. Finally, by analyzing the simulation model's calculation results, the fault arc's temperature characteristics are obtained, and experiments verify the simulation results.

The simulation results show that the temperature of the AC fault arc increases periodically, and the maximum temperature of the arc appears near the instantaneous peak value of the current. At this time, the influence range of arc temperature also increases significantly. The arc temperature is a cumulative process but develops rapidly in half an AC cycle. The arc current level and arc gap distance are the main factors influencing the maximum temperature of the arc, and the current level plays a decisive role in directly affecting the severity of the arc fire risk. The maximum temperature of the arc increases linearly with the current level below the 32 A current level, and the maximum temperature growth rate slows down after the 32 A current level.

The existing arc fault product standards can effectively limit the maximum temperature of arc fault and the influence range of arc temperature. However, even in the time specified in the standard, the arc center temperature can still reach more than one thousand degrees. Therefore, the standard can be improved by limiting the influence range of arc temperature to reduce the fire risk. Low current arc ignition ability cannot be ignored. The current level range covered by the relevant standards should be expanded, and the maximum removal time of 1 A and 2 A current level arc faults is recommended to be 3 s and 1.5 s, respectively. The standard action characteristic requirements should be refined to prevent arc fault hazards and reduce electrical fires comprehensively.

The high peak-to-average ratio of low-frequency pulse power loads seriously affects the safe and stable operation of airborne power supply systems. The conventional approach requires stacking numerous energy storage capacitors due to the DC bus voltage ripple limitation, which substantially increases the system’s volume. Although current active pulse power suppression method can reduce the required capacitance by increasing voltage fluctuations, the considerable power ratings and additional power processing stages of active suppression circuits impact system efficiency significantly.

This paper presents a low-frequency pulse power active suppression method based on voltage compensation. The active suppression circuit is inserted between the DC bus and the energy storage capacitor C_d. By compensating for the voltage difference between C_d and DC bus with the output voltage v_s of the active suppression circuit, the voltage range of C_d is not constrained by the DC bus, allowing for a reduction in C_d. Since the active suppression circuit only compensates for capacitor voltage fluctuations, its power rating and losses are much smaller than the average power of pulse loads, which greatly reduces the volume, weight, and losses. The active suppression circuit takes power from the DC bus. Considering that its input and output terminals are non-common ground and have a wide output voltage range, the LLC-DC transformer (DCX) cascaded Buck converter is chosen for the active suppression circuit. The LLC-DCX functions operate in an open loop as a high- frequency DC transformer, and a dual-loop control strategy is implemented for the Buck converter. The outer voltage loop adjusts the voltage fluctuation range of C_d, while the inner current loop suppresses the input current ripple.

The design guidelines for key parameters are also presented, with size and efficiency as the main considerations. The size of the power supply is influenced by C_d, while the power rating of the active suppression circuit affects system efficiency. Therefore, a detailed study of both aspects is conducted. The results reveal that once the load is determined, C_d decreases as the voltage fluctuation Δv_d increases, and the decreasing rate gradually slows. Additionally, the power rating of the active suppression circuit increases linearly with the average voltage V_dav and Δv_d. The lower limit of V_dav is also affected by Δv_d to ensure that the output voltage of the Buck converter remains positive. Therefore, a balance must be achieved between V_dav and Δv_d to optimize capacitance and power rating.

An experimental prototype is constructed. The experimental results are consistent with the theoretical analysis, and the active suppression circuit effectively regulates the voltage fluctuation range of C_d and suppresses the input current. Efficiency tests reveal that the active suppression scheme maintains an efficiency above 98.1% throughout the entire range, with a peak efficiency reaching 99.1%. This scheme is compared with existing active suppression schemes, showing clear advantages. In addition, results from various literature are normalized and compared.

Traditional control parameter design methods of grid-connected converters (GCCs) are usually carried out under rated operation conditions. The stability margin is generally characterized by the magnitude margin (GM) and phase margin (PM). The bandwidth of the phase-locked loop (PLL) needs to be sacrificed for enough system stability margin, which ensures that the system can operate safely under non-rated working conditions. Therefore, traditional parameter design methods make it difficult to achieve a compromise between the stability and rapidity of GCC. Furthermore, the relationship between the stability margin and the output limit of the system is difficult to obtain, which relies on simulations or experiments. To address this issue, this paper proposes a control parameter design method based on the system stable operation domain, which com- prehensively considers the variable working conditions and different stability requirements.

Firstly, the complex vector open-loop transfer function G_s(s) is derived, which can analyze the stability of the system in a wide operating range or under different parameters. Secondly, varying the values of the PLL and current loop control parameters, the feasible domain of control parameters can be obtained by numerical analysis. PLL and current loop are coupled to each other due to the grid impedance. Therefore, the phase-locked loop parameter has a stable parameter boundary. Thirdly, based on the upper limit of the obtained PLL parameter, the three-dimensional diagram between the PLL parameter and the output current of the dq-axis is plotted, which shows the stable operation boundaries of GCC under different PLL parameters. Finally, taking the operation margin as the stability margin, the PLL parameter can be flexibly designed to realize the balance between the stability margin and the dynamic performance. Theoretical analysis results show that the control parameter design method based on the stable domain can ensure the safe and reliable operation of the system. Compared with traditional parameter design methods, determining the value of control parameter based on operation margin can improve the dynamic performance of PLL. At the same time, the corresponding relationship between different stability margin and the output current limit of the system can be obtained. Finally, the simulation and experiment results verify the correctness of the theoretical analysis and the effectiveness of the proposed design method.

The following conclusions can be drawn from the theoretical analyses: (1) The derived open-loop complex transfer function can be used to plot the control parameter feasible domain and the stable operation domain of GCC. The PLL control parameter satisfying the operation margin can be obtained quickly without repeated trial and error in the parameter design. (2) The analysis results show that the grid strength is positively correlated with the parameter feasible domain and the PLL cutoff frequency is negatively correlated with the stable operation domain. The cutoff frequency value of PLL is limited by the current loop parameter. The smaller the operating current in the parameter design, the wider the range of PLL cutoff frequency, and the better the dynamic performance of the PLL. (3) The control parameter design method based on the stable operation domain can directly quantify the influence of stability margin on the limit of the output current, which can be used for obtaining the stable boundaries under different stability margin. At the same time, the control parameters of PLL can be flexibly designed according to the actual needs of rapidity.

LLC converters are widely used in the power stage of battery energy storage converters due to their excellent soft switching performance and low output impedance. Under low voltage and high current conditions, matrix transformers are often used on the secondary side of LLC to reduce current stress. In practical circuits, the volume of matrix transformers accounts for about 25% of the total main power, which seriously restricts the improvement of device power density. This paper proposes an integrated optimization design of LLC four-element-matrix planar transformer considering loss and parasitic parameters. Decoupling the influence of various structural parameters of transformers on parasitic parameters this method achieves efficient operation of transformers and controllable parasitic parameters. Voltage drop and oscillation are effectively suppressed.

Firstly, establish an accurate transformer loss model based on the proposed distributed magnetic core loss calculation method. Select the key parameters of the magnetic core that meet the efficiency and volume requirements: the radius of the magnetic core's central pillar r and the total width of the winding c. Afterward, select the winding layer structure. Establish a leakage inductance model based on transformer leakage magnetic field energy, determine the feasibility of leakage inductance integration through PCB thickness constraints, and design leakage inductance values.

The experiment shows that the secondary-side V_ds voltage oscillation is significantly reduced after integration optimization, reducing the parasitic capacitance value. By matching the resonant inductance to ensure that LLC operates in critical continuous mode at 300 kHz, the magnitude of the transformer's primary leakage inductance before and after integration can be calculated. The resonant inductance before integration is 1.8 μH, indicating the original edge leakage is 0.7 μH. After integrated optimization, the resonant inductance is 2.3 μH, indicating the original edge leakage is 0.2 μH. When operating in reverse, with the same input voltage of 3.2 V, the LLC output voltage rises from 34 V to 35 V. This means that the secondary edge leakage has decreased after integration. After resonance point matching, the secondary leakage inductance can be reduced from 33 nH to 12 nH. The secondary side V_ds oscillation caused by parasitic capacitance is close and small, which verifies the control effect of parasitic parameters.

This method can achieve the following effects. (1) The proposed distributed magnetic core loss calculation method for planar transformers based on P-B curves eliminates the influence of uneven magnetic density distribution on the accuracy of the magnetic core loss model, achieving accurate modeling of integrated transformer losses. (2) This method provides a judgment method for the feasibility of leakage inductance integration. (3) The prototype parasitic parameters can be controlled by accurately modeling the leakage inductance and parasitic inductance. This method provides theoretical support for designing and optimizing energy storage converters in LLC low-voltage and high-current scenarios.

The magnetic properties and loss characteristics of oriented silicon steel sheets exhibit significant deviation under stress. The traditional loss separation model generally overlooks the impact of mechanical stress on the loss characteristics, resulting in calculation errors. In recent years, most studies on the loss characteristics of oriented silicon steel sheets under mechanical stress have focused on qualitative analysis, with only a few studies making quantitative improvements to the loss separation model. This paper develops an improved loss separation model based on the traditional loss separation model by introducing stress terms into the hysteresis loss and excess loss.

Firstly, measurements from a single sheet tester with unidirectional stressing are utilized to analyze the stress dependency of the loss characteristics of the oriented silicon steel sheets. The experimental results demonstrate a significant enhancement in loss under compressive stress while exhibiting a slight decreasing trend under tensile stress. The magnetization mechanism in ferromagnetism explains the variation of the loss characteristics under mechanical stress. Secondly, the hysteresis loss and excess loss under stress are calculated based on the Bertotti traditional loss separation model. Since the stress component is not introduced into the hysteresis loss in the traditional loss separation model, the effect of stress on the hysteresis loss is only reflected by the hysteresis loss coefficient, leading to a significant error in the calculation of the hysteresis loss under stress. Although the excess loss parameter ${{V}_{0}}$, currently expressed by a constant coefficient, embodies the effect of stress, it fails to capture the effect of the applied mechanical stress on the losses of each magnetic induction intensity. Consequently, computational inaccuracies arise when employing the Bertotti traditional loss separation model.

Based on the correlation between parameters ${{V}_{0}}$ in excess loss, hysteresis loss, and stress, the traditional separation formula for losses is improved by introducing stress components into the excess loss parameters ${{V}_{0}}$ and hysteresis loss. An improved loss separation model is established and verified by varying the frequency of excitation and the type of oriented silicon steel sheet. The results indicate that the improved loss separation model can accurately separate and calculate the losses of oriented silicon steel sheets under different stresses while maintaining a remarkable precision level.

Experimental measurement and calculation analysis are performed, and the conclusions are as follows. (1) The excess loss parameter ${{V}_{0}}$ is correlated with stress, and incorporating the stress component into the excess loss parameter can effectively mitigate the calculation error caused by stress in the traditional loss separation model. (2) An improved loss separation model is proposed based on the traditional mode by incorporating the excess loss and hysteresis loss into stress-related functions. (3) The improved loss separation model is confirmed through testing with different frequency excitations and oriented silicon steel sheets, demonstrating its ability to accurately separate losses under different stresses.