Electric vehicles (EV) have the characteristics of both traffic and mobile load, and their charging behavior will have an interactive impact on the power grid. With the rapid increase in the number of electric vehicle and the continuous improvement of their penetration rate, charging guidance for large-scale EVs has become an important measure to alleviate the contradiction between local limited charging resources and strong charging demand. Therefore, considering the influence of future traffic information changes on navigation strategy, this paper proposes a fast guidance strategy for electric vehicle charging based on dynamic traffic inference.

First of all, a dynamic traffic information prediction model based on spatio-temporal self-supervised learning (ST-SSL) is established. A self-supervised learning (SSL) module for spatial and temporal heterogeneity of traffic data is designed to achieve accurate prediction of multi-period traffic flow information. Secondly, a multi-time dynamic impedance modeling method for urban road network considering future traffic information changes is designed, a charging navigation strategy considering multi-demand scenarios and multi-navigation objectives of users is established, and a solution method based on dynamic Dijkstra algorithm is proposed to realize the selection of the optimal charging station and the planning of the optimal navigation path. Based on the global charging navigation results, the service range of urban charging stations is dynamically evaluated, to achieve rapid charging guidance for electric vehicles. Finally, taking the actual road network of a certain area in Los Angeles as an example, the accuracy of the prediction model and the effectiveness of the guidance strategy are proved, which can effectively perceive the dynamic traffic information and quickly realize the service range division of urban charging stations and the charging guidance for electric vehicles.

In this paper, a fast guidance strategy for electric vehicle charging based on dynamic traffic inference is proposed, based on the case simulation results, the main conclusions can be obtained as follows. (1) The model based on ST-SSL can make full use of the spatial and temporal heterogeneity of traffic data, improve the prediction effect of traffic flow information, and provide an effective data basis for the construction of dynamic traffic impedance. (2) The proposed multi-scenario and multi-objective charging navigation strategy based on dynamic impedance can effectively perceive traffic information and take into account the diversified needs of users, effectively reduce the cost of charging navigation for different users, and reasonably guide the load distribution of electric vehicles. (3) The proposed dynamic Dijkstra algorithm can recommend the optimal path according to the future traffic information, which can be used as a navigation algorithm to plan the driving path, and can also recommend the customized optimal charging station according to the needs of users. (4) The division of charging station service range based on the global charging navigation results can effectively evaluate the service range of charging station, and provide an important reference for the construction planning of charging station. Based on the evaluation results, the charging navigation strategy is quickly assigned to each node, which effectively reduces the computing resource consumption of charging navigation.

Boost PFC converter is commonly utilized in rectifier circuits due to its ability to achieve a high power factor and low input current distortion. For the single-phase boost PFC converter, large-capacity and low-priced aluminum electrolytic capacitors (AECs) are typically employed to balance the instantaneous power deviation between the input and the output. However, the failure-prone nature of electrolytic capacitors may result in system instability or even collapse. Therefore, the real-time detection of electrolytic capacitor status information, assessment of its service life, and timely replacement of the soon-to-be-failed electrolytic capacitor can provide an important technical guarantee for the reliability of PFC power supply operation. This paper proposes an improved "zero-crossing removal interval" harmonic injection method for online detection of capacitance parameters to solve current zero-crossing distortion caused by harmonic injection. Additionally, based on the harmonic response of the bus voltage, the harmonic capacitor current reconstruction is achieved, and a model for calculating the C_R and R_E parameters without capacitor current sampling is constructed.

Firstly, the AC and DC input-output power action characteristics of the Boost PFC converter are fully utilized, i.e., the high harmonic current injection of the current control loop produces a high harmonic voltage splitting phenomenon on the output voltage. The two split harmonic voltage signals are employed to reconstruct the capacitor current; the capacitor's low-frequency impedance model is used to estimate C_R; a mid-frequency domain harmonic capacitor parameter computation model is established to estimate the R_E. In addition, the high harmonic current injection in the current loop inevitably results in an asymmetric zero-crossing distortion of the input current, directly affecting the accuracy of the capacitance parameter computation model. Consequently, the zero-crossing removal interval harmonic current injection method is employed to solve zero-crossing distortion caused by inter-area injection. The improved “zero-crossing removal interval” method avoids the reconstructed high-order capacitor current calculation error, enhancing C_R and R_E accuracy.

Eighteen types of capacitor conditions are selected for simulation calculation, and 48 W/72 W/144 W Boost PFC experimental prototypes are established. The proposed detection method is verified under an input voltage of 60 V, a switching frequency of 100 kHz, and an output voltage of 120 V. The results demonstrated that the method exhibits high detection accuracy under symmetrical injection conditions with a 10% zero-crossing removal interval, a 10 V injection amplitude, and a 650 Hz frequency. Furthermore, the improved “zero-crossing removal interval” method can achieve parameter detection error within 5% under different loads (100 Ω, 200 Ω, and 300 Ω) and capacitor conditions (196 mΩ/412 μF and 216 mΩ/617 μF), regardless of light or heavy loads.

This paper presents the following conclusions. (1) The proposed method considers the impact of current on distortion caused by harmonic injection. A “zero-crossing removal interval” harmonic injection method improves the accuracy of capacitance parameter detection. (2) In the “zero-crossing removal interval” method, the capacitor current is obtained through algorithmic reconstruction, which avoids high-precision capacitor current sampling. The harmonic injection is achieved by the control algorithm without additional hardware equipment. (3) The proposed capacitance parameter calculation model is derived based on the AC-DC power balance, making it straightforward to extend to similar AC-DC converters.

Implementing sensorless control is necessary to reduce the system volume of linear oscillatory machines (LOM) used in linear compressors and achieve efficient and reliable operation. The existing piston stroke observers have low observation accuracy and are susceptible to DC components, resulting in a decrease in system compression performance or cylinder collision risk. Therefore, this paper designs an improved high-precision piston stroke observer for linear oscillation machines based on a high-order generalized integrator (HOGI).

Firstly, a theoretical analysis is conducted on traditional back electromotive force integration, low-pass filter (LPF), and second-order generalized integrator (SOGI), elucidating the existence of integral saturation problems in back electromotive force integration, amplitude attenuation, and phase shift problems in LPF. SOGI performs slightly better than the previous two but still cannot eliminate the DC component. When operating at low resonant frequencies or in systems with large DC components, SOGI is no longer applicable. Secondly, in response to the shortcomings of traditional integrators, this paper adopts HOGI as a piston stroke observer. This method can eliminate the DC component, and no DC bias exists in the observed stroke signal. The paper also uses the forward Euler method to derive the digital implementation method of HOGI. Finally, experiments are conducted to compare SOGI and HOGI. The experimental results show that the piston stroke observed by HOGI is more accurate than SOGI without additional DC bias. Furthermore, when an additional 0.2 A DC bias is added, the piston stroke average offset observed by SOGI at the given value of 5 mm, 6 mm, and 8 mm is 1.367 5 mm, 1.365 mm, and 1.351 5 mm, respectively. The piston stroke observed by HOGI is unaffected by DC bias. Therefore, the piston stroke observer with HOGI is suitable for occasions with serious DC disturbance.

The contributions of this paper are as follows. (1) Based on traditional SOGI, an improved HOGI piston stroke observation structure is designed. Multiple filtering feedback characteristics are used to eliminate the influence of DC components on stroke observation results, improving the accuracy of the piston stroke observation. (2) The complex frequency domain method is used to analyze the pure integrator, LPF, SOGI, and HOGI. The superiority of HOGI is theoretically proven. (3) Based on the forward Euler method for discretization and digital implementation of HOGI, this method has the advantages of simple calculation and easy implementation.

The coupling between spatial-harmonic and time-harmonic currents in asymmetric multiphase motors (AMM) increases torque ripple and decreases efficiency, limiting their widespread application. Currently, active harmonic suppression strategies rely on complex filters or observers to extract harmonics and require the construction of numerous proportional resonance (PR) controllers at different frequencies, making the complexity and impracticality of harmonic suppression. Therefore, this paper proposes a single-frequency PR harmonic suppression strategy without filters based on the harmonic mapping law.

Firstly, based on the magnetic electromotive force equivalence principle, the universal space vector decoupling matrixes for AMM are established. Then, a mapping formula for harmonics of different frequency components on the subspaces is established. The general formula is decomposed into two independent components: amplitude and phase. The amplitude and phase mapping law of harmonics on the subspaces is derived according to the characteristics of the two components. Secondly, three criteria are proposed to search for the AMM with the minimum number of phases to ensure the unique mapping of harmonics. Based on the graphical representation of the mapping laws, the mapping trajectories of all harmonics are obtained to optimize the AMM topology and establish the subspaces for harmonic mapping. Then, based on the current phase-shifting method, a virtual AMM is constructed, and harmonics are extracted through the vector decoupling transformation subspaces. Finally, after unifying the frequency through linear space rotation transformation, PR controllers with the same resonant frequency are used to regulate harmonics.

Harmonic extraction and suppression experiments under steady-state and transient conditions are conducted using a dual three-phase motor. The extracted harmonic amplitudes can reach over 92% of the actual harmonics, demonstrating that the proposed algorithm can effectively separate harmonics. In the harmonic suppression experiment, the strategies of no harmonic suppression, current harmonic suppression under multiple synchronous rotating frames, and the proposed harmonic suppression strategy are compared. The proposed strategy decreases the proportions of the 5th, 7th, 11th, and 13th harmonic currents from 13.92%, 5.31%, 4.05%, and 2.96% before suppression to 3.02%, 0.43%, 0.39%, and 1.19%, respectively. The total harmonic distortion (THD) is decreased from 15.36% to 2.86%. Moreover, the harmonic suppression exhibited robustness under various operating conditions across the entire speed range.

The following conclusions can be drawn. (1) There are two harmonic mapping methods: full mapping with equal amplitudes and partial mapping with reduced amplitudes. The phase of mapping components can be divided into the α component leads or lags the β component by π/2. (2) Based on the harmonic mapping law, an optimal AMM topology selection criterion is established, and a virtual AMM is constructed, effectively avoiding the complex and inaccurate problem of harmonic extraction caused by constructing filters or harmonic observers. (3) The features of harmonic pair mapping on the selected subspace are that the difference in frequency order is equal, and the phase sequence is opposite. Thus, linear spatial rotation coordinate transformations are applied to unify frequencies, which enables single-frequency PR controllers with half the number of harmonics to regulate all harmonics.

The LLC converter plays a pivotal role in the infrastructure supporting electric vehicles, where efficiency and reliability are paramount. Its ability to efficiently transfer energy between different voltage levels makes it particularly suitable for EV charging stations, where power conversion efficiency directly impacts operational costs and environmental sustainability.

Synchronous rectification has emerged as a promising strategy for optimizing LLC converter performance. By replacing traditional diode rectifiers with active switches that operate synchronously with the converter's switching frequency, synchronous rectification minimizes energy losses and improves overall efficiency. However, existing synchronous rectification methods have faced challenges, such as complex control algorithms, sensitivity to load variations, and the need for high-frequency sampling.

Unlike conventional approaches that rely on high-frequency sampling for precise timing control, the novel synchronous rectification scheme utilizes a streamlined time-domain analysis. This approach dynamically adjusts the timing of the synchronous rectifier based on real-time feedback from the LLC converter's operating modes, ensuring optimal efficiency across a wide range of operating conditions with high-frequency sampling and alleviating the computational burden.

By reducing the complexity of control algorithms and eliminating the need for high-frequency sampling circuits, the scheme not only lowers manufacturing costs but also enhances reliability by reducing potential points of failure. This simplification is particularly advantageous in high-power applications like EV charging stations, where robustness and operational uptime are essential.

Simulation studies have validated the effectiveness of the proposed scheme under different load conditions and frequencies. Simulations have shown significant efficiency improvements compared to traditional methods, highlighting the scheme's potential to reduce energy losses and improve overall system performance.

Furthermore, experimental validation using a 6.6 kW prototype shows that the proposed scheme delivers consistent and efficient operation under steady-state and dynamic conditions, further supporting its potential for commercial EV charging infrastructure integration.

The adoption of the proposed synchronous rectification scheme promises to enhance the efficiency and reliability of LLC converters and accelerate the transition to electric mobility. As governments and industries worldwide prioritize sustainability goals and seek to reduce carbon footprints, improvements in energy conversion technologies play a crucial role in supporting the widespread adoption of electric vehicles.

In conclusion, the synchronous rectification scheme represents a significant step in evolving LLC converters for electric vehicle charging infrastructure. By overcoming traditional limitations and leveraging streamlined control strategies, the scheme enhances performance and contributes to the sustainability of transportation systems. As research continues to refine and optimize power conversion technologies, the ongoing advancements in LLC converter designs underscore their pivotal role in shaping a cleaner, greener future for global transportation.

Electrical isolation in advanced power supply systems typically relies on power frequency transformers or high-frequency isolation DC-DC converters. However, the transformers result in multiple converter stages and increase the system’s complexity and cost. To reduce the cost of advanced traction power supply system, this paper proposes a two-phase to single-phase non-isolated power electronic transformer (NI-PET) topology based on the existing traction transformer and has the advantages of fewer transformation stages and higher system efficiency.

Some switch states can result in short-circuit paths of the DC-link capacitance in NI-PET topology. The traditional modulation strategy fails to avoid the short-circuit paths. A three-dimensional space-vector pulse width modulation (3D-SVPWM) strategy is proposed based on the 3D space vector distribution diagram, taking the vectors of three ports as the coordinate axis. According to the number of available vectors, the 3D space is divided into different ranges. In addition, the proposed strategy determines the range of reference voltage vectors and selects available space vectors to complex the demanded reference vector. Finally, based on the V-v traction transformer, the simulation model and experimental platform are built.

Simulation and experimental results show that compared to the traditional space pulse width modulation (SPWM) strategy, the proposed modulation strategy can realize the stable operation of the system. When the load and grid-side voltage fluctuate repeatedly in a short period, the two-phase to single-phase NI-PET system restores a steady state within 0.2 s, the grid-side power factor remains above 0.99, and the THD of input and output current is less than 3%. With the same load, the three-phase current unbalance degree of the proposed topology is about 45% less than the traditional power supply system. It is verified that the proposed topology and modulation can adapt to harsh conditions such as continuous load and grid-side voltage fluctuations. Compared to PET, NI-PET avoids the loss caused by the isolation stage, thus significantly improving the efficiency. In the low-power experimental platform, the efficiency of NI-PET is about 10% higher than PET.

The following conclusions can be drawn. (1) The proposed two-phase to single-phase NI-PET topology can adapt to the harsh conditions of advanced traction power supply systems. It has the advantages of low cost and good power quality. (2) Compared to the traditional modulation strategy, the proposed one can avoid the short-circuit paths of DC-link capacitance. There is no short-circuit current that is much larger than the load current on the cascade line. (3) The proposed topology can achieve about 10% efficiency improvement in a low-power experimental platform and is expected to increase the efficiency by about 2% in industrial PET.

In the inverter-driven permanent magnet synchronous machine (PMSM) control system, high-frequency current harmonics near the switching frequency and its multiples are generated using space vector pulse width modulation (SVPWM), which brings high-frequency electromagnetic vibration. Therefore, a double random SVPWM control method combining random switching frequency and random zero vector is applied to the high-frequency current harmonic spectrum expansion. Meanwhile, the random number is generated by the improved Mersenne twister (MT) algorithm, which enhances the random performance of the random sequences and ensures the spreading effect of the double random SVPWM control method.

Firstly, random zero vector control can be achieved by changing the action time of the zero vector and reassigning the randomized zero vectors into the space vectors. Secondly, the switching frequency of the traditional SVPWM control method is fixed, and the random switching frequency control can be achieved by changing the fixed switching frequency of the inverter and dispersing the harmonics at the switching frequency and its multiples into the specified frequency domain. Thirdly, the random number is generated by the improved MT algorithm, which is applied to the double random SVPWM control of the permanent magnet synchronous machine to enhance the degree of freedom and spatial traversal of the random sequence. The new control method proposed is named LKMT-DRC.

Experimental verifications are conducted on a 4.4 kW fractional-slot permanent magnet synchronous machine. The PMSM phase current harmonics and vibration acceleration under the conventional SVPWM control and LKMT-DRC control are compared, and the vibration suppression effect of the LKMT-DRC control is analyzed using different spreading ranges. Under the inverter power supply mode, the harmonic frequencies introduced by the SVPWM control mode are mainly f_k±2f₀ and f_k±4f₀, and the frequency of the introduced high-frequency radial electromagnetic force wave is mainly f_k±f₀. Compared with the traditional SVPWM control mode, the high-frequency harmonics concentrated on the switching frequency. Its integer multiples can be effectively dispersed using LKMT-DRC control mode, and the vibration suppression effect caused by the high-frequency electromagnetic force wave can be significantly reduced. Meanwhile, the random numbers generated by the proposed LKMT algorithm can improve the randomness and spatial traversability of the random sequences, which ensures the effectiveness of the double-random SVPWM control method.

The contributions of the proposed double random SVPWM control method based on the improved MT algorithm are as follows. (1) A mathematical model of the high-frequency radial electromagnetic force introduced by PMSM under inverter power supply conditions is derived, and the effect of the high-frequency electromagnetic force under inverter power supply mode on motor vibration is analyzed. (2) The LKMT-DRC control method is proposed, which effectively reduces high-frequency harmonic content and suppresses high-frequency electromagnetic vibration. (3) The effects of different spreading ranges on the final damping under the LKMT-DRC control mode are analyzed, and the appropriate ranges are indicated.

Regarding the sensorless control system of permanent magnet synchronous motors (PMSM), this paper combines extended Kalman filtering (EKF) and improved inertial active disturbance rejection control (IADRC). By establishing a mathematical model under the new coordinate system and applying the EKF algorithm, the state of the motor is accurately estimated, thus ensuring the accuracy and stability of the control system. Aiming at the current harmonic disturbance caused by the sudden load change, this paper introduces the second-order oscillation function to optimize the traditional linear active disturbance rejection control and proposes an improved IADRC strategy, which significantly attenuates the harmonic disturbances and strengthens the system's immunity to disturbances.

According to the traditional mathematical model of the PMSM motor under the $\gamma \delta $-axis, the mathematical model of the PMSM motor under the estimated rotational coordinate system $\gamma \delta $ is constructed, and the angle ${{e}_{\theta \gamma }}$ between the dq-axis and the $\gamma \delta $-axis is directly estimated, eliminating the influence of the other observers. After that, through the mutual validation of simulation and the mathematical model, the second-order oscillating function is connected in parallel to suppress current harmonics. The 3rd, 5th, and 7th periodic harmonics with high harmonic contents are suppressed. Its effectiveness and stability are proved by Bode's plot and the Nyquist curve plot, respectively.

The EKF's direct estimation method of error angle ${{e}_{\theta \gamma }}$ in $\gamma \delta $ coordinate system is verified Through simulation and experiment, speed step, sudden load addition, and starting with rated load. Meanwhile, compared with the traditional PI control and LADRC control, IADRC plays a role in suppressing the low harmonics when the motor is running stably at 1 000 r/min with rated load. The 5th and 7th harmonic contents are reduced by 50.5% and 77.4% compared to PI. The IADRC algorithm based on the LADRC algorithm can suppress specific harmonics, with a 41.3% reduction in 5th harmonic content compared to the LADRC and a 49.4% reduction in 7th harmonic content compared to the PI. Comparative analysis of the three-phase currents after a sudden change in the rated load shows that compared to PI, the 5th harmonic content of the LADRC is reduced by 70.5%, the 7th harmonic content is reduced by 79.1%, and the 3rd harmonic content is reduced by 54.8%. Meanwhile, compared to LADRC, the 5th harmonic decreases by 44%, the 7th harmonic decreases by 13%, and the 3rd harmonic decreases by 88%.

Power electronic transformer with cascaded H-bridge (CHB-PET) can realize the flexible interconnection of AC/DC microgrid and renewable energy sources such as energy storage devices and DC loads. In a practical project, CHB-PET is connected to different bus segments through two short leads that are standby for each other. Considering the fault occurring AC side of CHB-PET, the spare short lead needs to be put into operation quickly to realize the rapid recovery of power supply. However, the conventional scheme cannot distinguish whether there is a fault before the spare short lead is put into operation, and there is a risk of connecting the faulty short lead. To solve this problem, this paper proposes a scheme based on the cooperative control of CHB-PET and DC microgrid, which achieves safe input of short leads by actively injecting characteristic voltage.

Firstly, CHB is blocked to achieve fault isolation after fault occurring. The energy storage device is switched to DC voltage control mode, maintaining the DC bus voltage and ensuring the normal operation of DC microgrid load and other equipment. Secondly, CHB is unlocked and switched to the U/f control. CHB-PET can inject characteristic voltage into the spare line to detect whether there is a fault point in the line. Furthermore, a fault detection method considering the current imbalance factor is proposed to reduce the time required for fault detection, so as to realize the rapid and safe investment of spare short lead.

The verification results on PSCAD/EMTDC simulation platform show that the scheme based on characteristic voltage injection can give accurate detection results when the spare line is fault-free. When three-phase fault, phase-phase fault, double-phase to ground fault and single-phase to ground fault occur in the spare line, the transition resistance of the phase-to-phase fault is 200 Ω, and the transition resistance of the ground fault is 300 Ω. The proposed scheme can also give accurate detection results. Through the simulation verification and experimental verification of the proposed scheme in different scenarios, the consistent results are obtained, which confirms the accuracy of the simulation model and the feasibility of the proposed scheme.

Through the simulation analysis, the following conclusions can be drawn: (1) The scheme uses the CHB-PET ontology to inject characteristic voltage with controlled amplitude and frequency into the standby line. According to the difference of electrical characteristics of the standby line in different scenarios, proposed scheme can accurately detect whether there is a fault in the standby line. (2) In three stages of the proposed scheme, the collaborative control of CHB-PET and DC microgrid energy storage device is used to ensure the normal operation of each equipment in the DC microgrid after the AC short lead fault, which is conducive to the rapid recovery after the fault. (3) In the fault detection stage of spare short lead, the fault detection criterion is constructed by using the product of the characteristic current imbalance factor and the current integral value. Compared with the direct use of the current integral value, the fault detection time under high resistance fault is reduced and the protection action speed is improved.