Electric aircraft has become a major development trend in the future aviation industry due to its advantages of low carbon and environmental protection. The air insulation of electric aircraft needs to withstand high-frequency voltage in high altitude. Therefore, this paper qualitatively studies the air discharge characteristics and microscopic mechanisms between needle-plate electrodes under different pulse voltage parameters and different humidity in the low temperature sub-atmospheric pressure environment of high altitude through simulation and experimentation.
Firstly, the pulse power supply was built by a 4-stage half-bridge Marx circuit. Then, the two-dimensional axisymmetric streamer discharge model of low-temperature sub atmospheric air was built, and three sets of Helmholtz equations were coupled to calculate the photoionization. Finally, the images of air streamer discharge under different conditions were captured by intensified charge coupled device (ICCD).
The following conclusions are drawn through simulation and experiment under the condition of low temperature and sub-atmospheric pressure: (1) The simulation outcomes reveal that when the reduced electric field strength remains the same, as the altitude increases, the breakdown voltage drops, the electron density gradually reduces, the electric field strength of the streamer head decreases, and the development speed of the streamer slows down. As the rising edge of the pulse grows, the electron density decreases simultaneously. When the discharge can be accomplished within one pulse, an increase in the pulse width has minimal effect on the discharge. Under the circumstances of low temperature and sub-atmospheric pressure, with the rise in humidity, the electron density increases concurrently, the peak value of the electric field intensity also rises, and the development speed of the streamer becomes faster. (2) The experimental results indicate that when the reduced electric field strength is consistent, with the increase of altitude, the penetration time of the streamer becomes longer, the channel brightness decreases, and the channel radius increases. When the pulse width of the pulse voltage is greater than the discharge time, the increase in the pulse width has no influence on the discharge process; when the frequency of the pulse voltage rises, the brightness of the streamer channel gradually intensifies; under the condition of low temperature and sub-atmospheric pressure, with the increase in humidity, the penetration time of the streamer becomes shorter and the brightness of the streamer channel increases. (3) Under the same conditions, the simulation and experimental results have a consistent conclusion regarding the development speed of the streamer. The influence of the pulse width on the discharge depends on whether the discharge can be completed within one pulse. The brightness of the streamer channel is positively correlated with the electric field intensity of the streamer head.

In fuel cell hybrid systems, the degradation processes of fuel cells and power batteries are highly inconsistent. The excessive consumption and premature end of life of one power source can disrupt the balance of the power system, deplete the performance of the other power source, accelerate the aging of the entire power system, and negatively affect vehicle economy and system durability. Consequently, it becomes challenging to achieve optimal fuel economy and system durability simultaneously. To address this issue, an optimization strategy based on condition prediction and coordinated power source life degradation is proposed.
Firstly, to improve prediction accuracy, operating conditions are categorized into three typical states: low-speed, medium-speed, and high-speed. An upper-level Markov Chain Monte Carlo (MCMC) prediction model is established based on historical conditions to predict the tram's operating conditions. This prediction provides more information for the lower-level energy management strategy to optimize system energy distribution. Secondly, in the lower-level energy management strategy, the hydrogen consumption of the fuel cell and the equivalent hydrogen consumption of the auxiliary power source are analyzed. A continuous degradation model for the fuel cell and power battery is established, introducing optimization objectives and adaptively adjusting the weights of each objective online to optimize the multi-objective function. Finally, the proposed strategy is compared with the traditional equivalent consumption minimization strategy (ECMS) and the external energy maximization strategy (EEMS).
Results show that at the end of the entire operating condition, the proposed strategy's hydrogen consumption is 99.61 g, the degradation rate difference between the dual power sources is 0.000 66%, the system efficiency is 81.66%, the power fluctuation range is -800 W to 800 W, and the stress on the power battery and supercapacitor is 117.5 and 176.4 respectively. Compared to the ECMS strategy, with a hydrogen consumption of 115.1 g and system efficiency of 77.64%, the proposed strategy improves fuel economy and system efficiency by 15.6% and 5.2% respectively. Compared to the EEMS strategy, with a dual power source degradation rate difference of 0.014 4% and system efficiency of 79.77%, the proposed strategy reduces the degradation rate difference by 21.82 times and improves system efficiency by 2.4%. Additionally, the power fluctuation range under the proposed strategy is significantly reduced compared to the -1 000 W to 1 000 W range under both the ECMS and EEMS strategies, resulting in a smoother power source power curve. Under the ECMS strategy, the stress on the power battery and supercapacitor is 156.6 and 215 respectively, while under the EEMS strategy, the stress is 156.8 and 226.6 respectively. The proposed strategy reduces the stress on the auxiliary power source compared to the ECMS and EEMS strategies, decreasing excessive consumption and resulting in a more reasonable power distribution.
Comprehensive simulation analysis reveals the core advantages of the proposed strategy: (1) Establishing an MCMC prediction model for condition prediction improves the adaptability of the energy management strategy to operating conditions, achieving more reasonable, precise, and efficient energy control and reducing damage to the hybrid power system. (2) Overcoming the poor fuel economy of traditional ECMS and the high inconsistency in power source degradation of EEMS. (3) Achieving superior fuel economy and system durability, thereby extending the lifecycle of fuel cell hybrid systems.

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.

The arc plasma torch can be used for pre experiments on ground erosion performance testing of spacecraft flight materials，which can save costs. The three-phase AC arc plasma torch has the advantages of simple power supply and reliable operation. The hollow electrode structure with dual inlet channels can not only improve the electrode life, but also achieve a wider range of power control. However, the design of plasma torches with this type of electrode structure is more complex and there is limited research and application in China. A three-phase AC plasma torch with magnetic motion, tangential inlet, and supersonic jet was developed and numerically modeled and experimentally studied.
Firstly, a three-dimensional turbulent MHD multiphysics coupling simulation model of a hollow electrode three-phase AC arc plasma torch with a dual end inlet structure was established, and the flow state and electric thermal characteristics of the arc plasma inside the torch were obtained. Secondly, the influence laws of air intake, working current, air intake distribution ratio, and working frequency on the electric field, magnetic field, temperature field, flow field distribution, and arc characteristics inside the plasma torch were studied and revealed. Finally, the correctness of the numerical model was verified by comparing the arc voltage, nozzle outlet temperature, and arc root position under various operating conditions in simulation and experiment.
The conclusion drawn from the study is as follows: (1) In a three-phase AC plasma torch, aerodynamic and electromagnetic forces dominate the flow characteristics of the arc root. During the process of increasing the intake volume from 30 g/s to 60 g/s, the cooling effect of the gas flowing along the wall is greater than the heat generated by the arc column, resulting in a downward trend in temperature; And the larger the intake volume, the more obvious the compression effect of the cold air layer on the arc, and the higher the arc pressure; The higher the working current, the higher the plasma temperature and jet velocity. (2) In a hollow electrode AC plasma torch with dual inlet ducts, changing the air intake distribution ratio can alter the position of the arc root along the electrode axis and the magnitude of the output power. Increasing the air intake distribution ratio can make the arc more significantly stretched in the axial direction, the arc longer, and the arc root closer to the arc back cover. (3) When the operating frequency is 1 kHz, the arc has a more stable motion trend, and the rotation speed of the arc root is five times that of the power frequency. The contact area with the electrode is reduced, which reduces the degree of electrode erosion and can improve the electrode life.

With the increase of power and frequency of wireless power transmission systems, requirements for the control performance of power transmission and real-time high-frequency data interaction between the power transmitter and receiver continue to increase. This paper proposes an implementation method for low-cost and highly robust wireless power and signal transfer (SWPDT). Based on the traditional magnetically coupled wireless power transfer (WPT) system structure, the two metal-shielded pole plates on the outside of the magnetically coupled coil provide an independent capacitive channel for data transmission, and the magnetically coupled mutual inductance coil provides an independent inductive channel for power transmission, which achieves decouples energy transmission and signal transmission. The six-plate capacitive coupling is constructed under the coil parasitic capacitance. The mathematical and physical models of six-plate capacitive coupling are constructed, and the fourth-order resonant network is built to achieve full-duplex communication through four blocking networks and compensation structures. The overall cost and size of the WPT system are significantly reduced. The crosstalk of power transmission on signal transmission is reduced without changing the power transmission capability, and the power transmission frequency no longer restricts the transmission frequency. Finally, a 50 W power transmission prototype is constructed. The power transmission efficiency reaches 80% under the 17 cm coil distance condition. The full-duplex parallel transmission of power and signals is achieved within a serial communication bit rate range from 240 to 800 kbit/s. The BERs can be maintained at a low level, and the effects of the pole plate offset on the signal and power transmission are verified. The transverse drift ratio reaches 87.5.0%. In the case of the pole plate offset with an 87.72% lateral drift ratio, the signal transmission efficiency of the system is only 22.66%. Under the magnetic shielding function of the metal pole plate, the signal transmission is robust under extreme working conditions, improving the reliability of the power transmission process. The shielding pole plate reduces the power transmission efficiency but has a significant shielding effect on electromagnetic leakage. Compared with the existing wireless energy and data synchronous transmission technology in transmission efficiency, transmission distance, signal rate, and BER, the correctness and feasibility of the proposed method are verified.

To achieve continuous and real-time stress optimization control of the dual active bridge converter under power transmission or voltage fluctuations, it is crucial to study the patterns between modes and among optimization control variables in modes. However, current research needs depth, and functional expressions of stress optimization control variables are complex.

This paper employs genetic algorithms for stress optimization. The intrinsic laws among the optimization variables in each mode are elucidated through the optimization results. An innovative trigonometric function polar coordinate method is adopted to derive the corresponding optimization control variable function expressions.

Firstly, based on waveform equivalence simplification and the principle of waveform and energy transmission, the four locally optimal modes are identified from the twelve working modes, which exhibit low stress or effective values in different power ranges. It reduces the number of modes that require optimization, which reduces the optimization burden.

Secondly, the stress of the four modes is optimized, and the optimization results are compared to determine the laws governing the optimization variables in different power ranges with different k values. Through systematic analysis, the laws of four local optimal operating modes in the low/high power section can be obtained.

Thirdly, the expressions with optimization variables are obtained by substituting these laws into the corresponding power transfer expression. The optimized variables are converted into trigonometric polar coordinate forms through the trigonometric function polar coordinate method. The expressions for the minimum current stress function and its optimization control variables are obtained by substituting optimized variables into the stress expression to obtain the minimum stress value.

Compared with the current stress in the full power range for four local operating modes, the optimal mode and optimal control variables for each power segment across the entire power range are selected, thereby achieving global optimization control. The innovations in this study are presented.

(1) Analyze and contrast the current stress optimization results for different voltage adjustment rates k to discern the laws among the optimized variables across the four local optimal modes in various power ranges.

(2) The power constraint and trigonometric polar coordinate methods are utilized to derive a precise expression for the optimal stress control variables. The globally optimal control variables are selected by comparing the current stress of four local optimal modes.

The following conclusions can be drawn. (1) Under the buck operation conditions of stress optimization for both forward and reverse power transfer across the entire power range, mode 1.1 is globally optimal during low forward transmission power when 0<P<k²(1-k); mode 1.4 becomes globally optimal during high forward transmission power in the range k²(1-k)<P<k/2. Similarly, for low reverse transmission power, mode 2.1 is globally optimal in the range k²(k-1)<P<0, and mode 2.3 becomes globally optimal during high reverse transmission power when -k/2<P<k²(k-1). (2) The stress optimization control under TPS modulation improves the efficiency of the DAB converter compared to other modulation strategies. Notably, it exhibits a significant enhancement under the low-power segment and high-voltage mismatch scenarios.

The multi-phase open-winding induction motor and its adaptive H-bridge multi-phase inverter system have received extensive attention due to their advantages of small torque ripple, strong fault tolerance, and easy power capacity expansion. This paper analyzes the modeling of the multi-phase open-winding motor system and speed sensorless control technology to achieve high degrees of freedom control and low switching frequency characteristics in a twelve-phase, large-capacity, open-winding motor system. The simulation and experimental verification are conducted to enhance the operating performance of the low-switching-frequency multi-phase open-winding motor system.

The twelve-phase open-winding induction motor system and its equivalent three-phase simplified model are established. The equivalent three-phase full-order observer model and its speed estimation method are presented. The full-order observer used in speed sensorless control has the advantages of low control bandwidth requirements and a wide range of observation speeds. However, the switching frequency of the H-bridge large-capacity inverter supporting the ship’s multi-phase open-winding induction motor is low, which inevitably increases the digital discretization error of the full-order observer. This paper derives the full-order flux observer models based on the forward Euler method, the simplified second-order discretization method, and the proposed Adams fourth-order discretization method. Then, the steady-state error and observer stability are compared using the F-norm and pole diagram. Theoretical analysis reveals that the full-order observer, based on Adams' fourth-order discretization method, achieves the best discrete accuracy and stability of the observation system while minimizing the computational complexity of the digital control system.

A simulation model and a test platform for a twelve-phase, 25 kW open-winding induction motor with speed sensorless control have been developed. The results show that, compared with the forward Euler method and the simplified second-order discretization method, the observation results for speed, current, and flux based on the Adams fourth-order discretization method are almost consistent with the actual values. Through the speed sensorless closed-loop speed regulation test and load mutation test, it is further verified that the full-order observer based on Adams' fourth-order discretization method exhibits good speed regulation and load-carrying capacity, which can achieve better dynamic and steady-state performance under both extremely low and high-speed conditions. The full-order observer discretization method can provide technical support for applying speed sensorless control technology to low switching frequency multi-phase open-winding motor systems.

Accurate load torque identification helps to improve the load disturbance resistance of complex nonlinear loaded permanent magnet drive systems. The sliding mode observer (SMO) has become a commonly used algorithm for load torque identification due to its advantages of high robustness to noise, fast response speed, and simple structure. However, the shortcomings of this algorithm, such as high-frequency chattering and slow response speed, limit its application in electric drive systems. This paper proposes a new adaptive sliding-mode load torque observer to solve the problem of the inherent contradiction between the convergence speed and high-frequency chattering of conventional sliding-mode observers.

Firstly, from the perspective of quasi-sliding mode, the conventional sign function is replaced by the saturation function to suppress the high-frequency chattering of the load torque estimate. The sign function can effectively suppress the chattering phenomenon of SMO, but it still fails to balance the convergence speed and observation accuracy. Second, an adaptive convergence rate is designed to introduce an exponential convergence term based on the conventional isochronous convergence rate. The adaptive gain of the isochronous convergence term is designed to make the sliding-mode observer adaptively adjust the convergence speed along with the change of the system state. Thus, the observer has a short convergence time and strong robustness, and the high-frequency chattering phenomenon of the sliding-mode observer in the steady state is suppressed. Finally, this paper introduces the average estimated value of the load torque in the conventional slip mode identification algorithm and adds it to the feedback loop of the speed observer. The improved load torque observation algorithm can suppress the chattering of the estimated torque by adjusting the feedback gain g. Since the load torque indication signal U can characterize the load torque change without additional delay, it can be directly involved in the speed estimation. Therefore, the proposed algorithm has a fast response speed during transient processes while considering the chattering suppression of the system. Based on the principle of sliding mode variable structure control, the adaptive rate of feedback gain coefficient g is designed.

Simulation and experimental results show that under varying speed and load disturbances, the proposed adaptive SMO has less chattering than traditional SMO and super-twisting SMO. Additionally, the adaptive SMO converges faster than traditional SMO and performs comparably to super-twisting SMO. In load disturbance experiments at a reference speed of 600 r/min, the speed fluctuations for no torque feedforward, traditional SMO with torque feedforward, and adaptive SMO with torque feedforward are 72.5 r/min, 56 r/min, and 35.5 r/min, respectively, with system recovery times of 0.7 s, 0.65 s, and 0.5 s. To further verify the impact of inertia parameter mismatch on the adaptive SMO, inertia was set to 2, 5, 0.5, and 0.2 times the rated value, with the maximum deviation in load torque observation being 6.7 N·m. The results indicate that the impact of parameter mismatch is not significant.

The following conclusions can be drawn. (1) The designed adaptive SMO has a simple structure and high stability, is easy to implement, observes the load torque quickly and accurately, and requires fewer parameters. (2) Compared with the conventional SMO, the proposed adaptive SMO has less chattering and faster response speed during the transient change of the load torque. (3) The proposed adaptive SMO is more suitable for the scenario of variable load torque than the conventional SMO. The experimental results show that when the load torque recognized by the adaptive SMO is used as the feedforward term of the reference torque, the response speed and load disturbance resistance of the heavy-duty chain drive system can be effectively improved.

Line-starting permanent magnet synchronous motors (LSPMSM) are different from other permanent magnet motors due to their double-sided slotted characteristics of the stator and rotor, making it difficult to analyze the cogging torque. The overall optimization of motor cogging torque and torque ripple rate is also challenging. This paper optimizes the rotor design of the LSPMSM based on multi-objective particle swarm optimization algorithm, considering the saturation performance of the motor.

Firstly, this paper establishes the relationship between harmonic magnetomotive force and cogging torque to predict the cogging torque of the LSPMSM. The cogging torque is analyzed as a dynamic function relationship of various motor parameters, providing corresponding optimization parameters for the subsequent optimization of the prototype. At the same time, under the premise that the maximum magnetic energy product of the permanent magnet remains unchanged, the relationship between the saturation degree of the motor and the parameters of the permanent magnet is determined, and the selection range of the motor's permanent magnet parameters is determined based on this relationship. Define three working states of the motor: unsaturated, peak saturation, and after saturation, to make the analysis and optimization results of the motor more accurate.

Secondly, combined with response surface methodology (RSM) and multi-objective particle swarm optimization algorithm (MOPSO), this paper proposes a comprehensive optimization strategy to optimize key objectives such as motor cogging torque, torque ripple rate, and efficiency. The optimal design solutions in different regions can be obtained by using the response surface algorithm to classify numerical groups and shorten the computation time of the particle swarm optimization algorithm. The optimal solutions under six different conditions are determined after considering whether the stator is skewed and the three working states of the motor.

Finally, simulation analysis verifies the relationship between cogging torque and harmonics under different saturation states, the trend of no-load back electromotive force, and the main harmonic order changing with the number of slots per pole of the rotor. An experimental platform is built to verify the accuracy of theoretical and simulation analysis. This paper provides optimization solutions for the design of motors of the same type.

In distributed residential photovoltaic (PV) power generation systems, microinverters have attracted significant attention due to their benefits, including component-level maximum power point tracking (MPPT), plug-and-play flexibility, and high security. However, most existing microinverters are designed for grid-connected applications and are primarily suited for single-phase two-wire systems. Additionally, the intrinsic double-line-frequency power fluctuation problem greatly limits the increase in power density and reliability of microinverters. This paper proposes a novel voltage-source high-frequency-link (HFL) microinverter with double-line-frequency power decoupling capability, which is compatible with various single-phase distribution grids.

On the primary side of the proposed microinverter, a Boost converter is integrated with the full bridge of the HFL microinverter by sharing the switches. The integration has high voltage gain and additional double- line-frequency power decoupling capability. On the secondary side, a novel structure with three-wire output is proposed to be compatible with single-phase two-wire and single-phase three-wire power systems. Due to its voltage-source-inverter (VSI) characteristics, the proposed microinverter is suitable for grid-connected and islanded applications.

This paper introduces the circuit structure of the proposed microinverter. A soft-switching modulation is proposed along with its logic implementation. Operation modes during a switching cycle and the soft-switching characteristics of each switch are analyzed. The proposed microinverter features a three-wire output, and the two phase-to-neutral output voltages are auto-balanced. Therefore, the specific balancing theory is also analyzed. The double-line-frequency power decoupling principle is presented and analyzed. To meet the required input voltage range and ensure acceptable voltage stress on switching devices, design considerations for key circuit parameters are presented, including the turns ratio of the high-frequency transformer (HFT), the average value of the decoupling capacitor voltage, the inductance of Boost inductor, and the capacitance of the decoupling capacitor.

Moreover, grid-connected and islanded closed-loop control strategies are proposed. Finally, a 600 W prototype is built to verify the proposed topology and strategies. Steady-state and dynamic test results for grid-connected and islanded operations are provided.

The following conclusions can be drawn. (1) The proposed microinverter achieves high gain and double-line-frequency power decoupling, resulting in a 22 V to 55 V wide input voltage and an MPPT efficiency above 99% with a 100μF input capacitance. (2) A special three-wire output is proposed for single-phase two-wire and single-phase three-wire distribution grids, with the two phase-to-neutral voltages auto-balanced without dedicated control. (3) The proposed microinverter operates in both grid-tied and islanded applications, and the closed-loop control strategies ensure stable steady-state operation and fast dynamic response.