In the current power system, the conversion between DC and AC is widespread, and the DC-side harmonic problem is prominent. A DC Active Power Filter (DC-APF) is a good solution for suppressing low-frequency current ripples. Currently, the control method for DC-APF commonly employs dual-loop control of voltage and current, where the outer voltage loop limits the response and accuracy of the inner current loop. To meet the requirements of current ripple tracking for fast response and high precision, the output function of the DC-APF is reconstructed to integrate the voltage and current of the DC-APF. A precise linearized model of DC-APF is achieved with no high-order terms being ignored. Then, a unified single-loop control strategy, integrating DC-APFʹs voltage and current control, can be obtained based on the precise linearized model. It has a significantly better dynamic/steady-state effect. Due to the strong dependence of the converted precise linearized model on parameters, the robustness of the unified single-loop controller is poor. Sliding mode control is further combined with the unified single-loop control, which can weaken its dependence on accurate circuit parameters. Therefore, the control method proposed in this paper has the advantages of fast response, high accuracy, and strong robustness. Finally, the correctness and effectiveness of the proposed method are verified in comparison with conventional dual-loop control.

Bidirectional asymmetric power transmission demand widely exists in DC microgrid with high distributed power penetration and custom-designing the bidirectional power rating of the DC converter rather than designing it symmetrically is beneficial to reduce the cost. However, soft-switching operation in the whole load range is challenging to existing schemes. In this paper, a near-zero switching loss asymmetrical isolated bidirectional DC converter (AIBDC) with two independent paths at the low voltage (LV) side is proposed, four silicon diodes are adopted to form forward path, while four fractional silicon carbide metal oxide semiconductor field effect transistors are used in the reverse path. With the proposed triangular modulation strategy, not only turn-on loss but also turn-off loss of switches can be eliminated significantly in the whole load range and near-zero switching loss can be obtained. Soft-switching characteristics of the proposed AIBDC with the considerations of dead time and voltage fluctuation are analyzed in detail. Parameters designing procedure and control strategy are given. To verify the effectiveness of the proposed AIBDC, a 280∼330V/120V/40kHz/2kW experimental prototype is built. The highest efficiency of the proposed AIBDC is 98.7%.

The active-neutral-point-clamped (ANPC) converters typically feature more degrees of freedom and the potential of optimized loss distribution. The existing hybrid ANPC has advantages in terms of efficiency and cost, but it has inadequate loss optimization under varying operating conditions. To address this, a novel high-efficiency Si/SiC hybrid switch (HyS) topology coupled with a dual-current-path modulation strategy is proposed to reduce losses. The proposed converter topology effectively optimizes switching losses through a strategic implementation of four active HyS switches, when a novel modulation strategy concurrently reduces conduction losses by establishing dual current paths during zero state. The synergy between the two enables the proposed scheme to not only reduce the total loss but also achieve an effective distribution of conduction losses, thereby further enhancing the overall system performance. In this paper, the structural configuration and operational principle of the proposed topology are first analyzed, followed by the design of its corresponding modulation strategy. Subsequently, a comprehensive loss model is established to evaluate the loss characteristics inherent to the proposed topology and modulation strategy. Simulation studies are conducted to compare the loss distribution and efficiency performance among different ANPC schemes, highlighting the superior performance of the proposed scheme. Finally, a three-phase three-level HyS-based HANPC converter prototype is constructed and tested. Experimental results are presented to verify the enhanced performance of the proposed converter topology and modulation strategy.

With the development of renewable energy, the DC distribution system has become a hot issue due to its high efficiency and stability. The power quality problems, such as voltage deviation and current ripple, as well as the transient voltage sag, have become the key issues in the planning and design of DC distribution systems. The existing DC power quality management devices only address a single power quality issue and are difficult to comprehensively deal with the abovementioned power quality problems. Therefore, to achieve the comprehensive management of various power quality issues, this paper proposes a multifunctional power quality management device. For the low-frequency current ripple control of the DC power distribution system, the DC active power filter (DC-APF) is introduced. Meanwhile, by combining the advantage of bidirectional power flow of the Dual active bridge (DAB), the governance of problems such as voltage deviation and voltage sag is achieved. Based on the above ideas, a multi-functional DC power quality management device and its control strategy are proposed. Finally, through the experimental platform, the feasibility and effectiveness of the topological structure and control strategies proposed in this paper are verified.

Isolated bidirectional DC converters (IBDCs) serve as a critical component in DC microgrid. However, the variation of load introduces significant challenges to the soft-switching operation of IBDCs. To cope with this, an IBDC topology using hybrid switches approach based on dual-transformer structure is presented in this article to improve efficiency in the full-load-range. Collaborating with a quasi-zero switching-loss modulation and quasi synchronous rectification strategy, the QS-IBDC can maximumly eliminate not only turn-on loss but also turn-off loss across the full-load-range. To validate its performance, a 500W/200V/80V/10kHz prototype that copes with 190V~205V input voltage was built. Recorded efficiencies peak at 96.8% in reverse mode.

Owing to the capability of both reactive power compensation and single-phase-to-ground fault control, multifunctional grid-connected active arc-suppression devices (GAASDs) have recently attracted extensive attention. However, most traditional GAASDs suffer from high cost, large volume, and difficulty in energy self-balancing of the grounding arm. To address these issues, a multifunctional GAASD based on a hybrid cascaded converter (HCC-GAASD) is proposed in this article. The proposed HCC-GAASD consists of a three-phase four-arm neutral point clamped (NPC) unit and cascaded H-bridge (CHB) units, which are connected in series. In this structure, the HCC-GAASD makes full use of the advantages of the high withstanding voltage of the NPC unit and the high equivalent switching frequency of CHB units, thus reducing the cost and volume. In addition, the energy fluctuation mechanism and energy self-balancing constraints of the fourth-arm CHB unit are analyzed in detail. An energy self-balancing modulation strategy is proposed to maintain the DC voltage stability of the fourth-arm CHB unit without additional power supplies. Simulation and experimental results demonstrate the validity of the proposed topology, modulation and control strategy.

This study proposes an adaptive variable structure control strategy for charging stacks to address the issues of reduced conversion efficiency during wide-voltage-range operation and insufficient module allocation flexibility in multi-vehicle scenarios. By dynamically adjusting the number and series/parallel configurations of modules, the strategy ensures that modules consistently operate in high-efficiency regions, thereby achieving high energy conversion efficiency across a wide voltage range. First, the operational characteristics of the three-phase PWM rectifier and the dual active bridge (DAB) converters are analyzed, and their corresponding mathematical and loss models are established. Subsequently, the charging demands acquired by the charging stack are analyzed, and an adaptive variable structure control strategy is designed based on the module margin of the charging stack. When modules are surplus, the feasible range of series/parallel configurations for each port is constrained, and module combinations are optimized with the objective of minimizing system losses. When modules are insufficient, an adaptive module reservation scheduling strategy is employed to ensure temporal fairness in vehicle connection order while supplying power to multiple vehicles, effectively reducing the average charging time. Finally, the effectiveness of the proposed control strategy is validated through simulations conducted on the Matlab/Simulink platform. Results demonstrate that compared to traditional fixed-structure systems, the proposed strategy improves peak efficiency by up to 2.53% at 400 V and 1.12% at 800 V, while reducing the average charging time by 3.07% in the disconnection scenario and 12.1% in the asynchronous access scenario.

Si/SiC hybrid switch synergistically combines the superior switching characteristics of SiC MOSFET with the cost advantage of Si IGBT, presenting an economically viable approach for enhanced power conversion efficiency. However, the performance of this hybrid configuration is primarily governed by the switching pattern, which exhibits significant load current dependence. To address this challenge, a novel load-adaptive multi-pattern switching strategy based on active gate driver (AGD) is proposed in this paper. Firstly, the switching characteristic analysis of the hybrid switch is conducted, the coupling effects of gate drive voltage and current on electrical stress and power loss are systematically analyzed. Subsequently, an AGD circuit based on transient voltage feedback is designed to dynamically regulate the gate current during switching transients. Finally, based on the device's safe operating area, three load current intervals are defined. The proposed strategy adaptively selects among three switching patterns according to the instantaneous load current, which can optimize the power loss during light-load operation while suppressing current overshoot under heavy-load conditions. Compared with the conventional 15 V and 20 V strategies, the switching loss is reduced by at least 12.69% and the current stress is reduced by up to 64.3%, respectively. Experimental results demonstrate the effectiveness of the proposed strategy.

Isolated bidirectional DC converters (IBDCs) serve as a key component in DC power grid for their features such as bidirectional power regulation and soft-switching operation. However, the variation of load introduces significant challenges to the soft-switching operation of IBDCs. To cope with this issue, an IBDC scheme using a partial power processing approach based on dual-transformer structure is proposed in this article to enhance efficiency in the full-load-range (FLR). Collaborating with a modified triangular modulation and quasisynchronous rectification strategy, the proposed scheme can maximally eliminate not only turn-on loss but also turn-off loss across the FLR. Furthermore, the operational modes of this proposed scheme are outlined, and the soft-switching characteristic is analyzed thoroughly with the consideration of load ratio, dead time, and input voltage variation as well. Then, designing considerations of transformer turns ratio and inductance in the proposed scheme are developed to ensure soft-switching operation in the FLR. To validate its superior performance, a 2.0 kW/300 V/120 V/40 kHz prototype that copes with 280 similar to 330 V input voltage was built. Recorded efficiencies peak at 98.77% in backward mode and 98.7% in forward mode, with consistently high performance maintained across the full load range.

High-power-density design is the developing trend of permanent magnet synchronous motors (PMSMs), and the accurate prediction of internal temperature is a practical and necessary scientific research. In this article, the TimesNet model is utilized for the high-precision temperature estimation of PMSMs to capture multiscale thermal dynamics. It is observed that the generalization capability of the TimesNet model could be significantly improved by incorporating a transfer learning (TL) strategy with efficient fine-tuning, which guides the model adaptation across cross-condition and cross-motor scenarios. In addition, the maximal information coefficient (MIC) method is chosen to select dominant thermal features from nonlinear coupled variables, which reduces the computational redundancy and improves the physical interpretability of the selected features. Experimental results demonstrate that the proposed method achieves superior estimation accuracy and robust generalization with reduced training samples.

Acquiring accurate temperature data for Lithium-ion batteries (LiBs) under dynamic driving conditions is crucial for ensuring their safety, performance, and extended lifespan. However, precise temperature estimation presents significant challenges due to environmental variations, limitations in sensor deployment, and complex driving cycles. To address this issue, this paper proposes a multi-scale feature-driven temperature estimation method for LiBs under driving scenarios using physical-enhanced transfer learning. First, a physical-constrained data enhancement (PCDE) approach is designed for driving conditions. By considering frequency matching and battery electrothermal characteristics, enhanced data that comply with physical laws are generated. Then, a TimesNet temperature estimation model is constructed to leverage its multi-period decomposition capability, enabling the extraction of multi-scale and multi-period features from current and voltage signals under dynamic conditions. Finally, a transfer learning strategy is developed by integrating the PCDE approach with the TimesNet model. Experiments are conducted across various driving scenarios using two datasets. The results demonstrate that the proposed method maintains excellent generalization performance under diverse and complex driving scenarios, with RMSE consistently below 0.4°C. The proposed method provides an effective technical solution for improving the temperature estimation accuracy of battery management systems in electric vehicles under complex driving scenarios.

Hybrid Switch (HyS) is consisted of a high-current Si-insulated gate bipolar transistor (IGBT) and a low-current Silicon Carbide (SiC)-MOSFET connected in parallel, which has been widely studied due to their high efficiency and low cost. In general, to realize the zero-voltage conduction of IGBTs, the switching timing of the Hys is usually chosen to turn on the SiC earlier or at the same instant. However, HyS will have current overcurrent stress problem in practical applications, resulting in the maximum current rating being limited. In this paper, an active drive circuit is proposed to suppress the SiC MOSFET current overshoot by extracting part of the driving current during the SiC current rise phase, so as to ensure the operational reliability of the hybrid switches. A double-pulse test platform was built to verify the proposed driver circuit under different load current conditions. The experimental results show that compared with the conventional gate driver (CGD) circuit, the Si/SiC hybrid switches with the active gate driver(AGD) circuit proposed in this paper suppresses the current overshoot of the SiC by 38.3 %, 28.4 %, and 22 % in the heavy-load, medium-load, and light-load conditions, respectively, when the drain resistance is selected to be 3 Omega. The peak current of the SiC is within the limit of the safe operating area, while the increased switching loss is within the acceptable range.

With the popularization of electric vehicles, how to efficiently manage their charging behaviors has become a hot topic in the field of energy management. Flexible charging strategies can not only enhance user experience but also play a crucial role in achieving stable grid operation, energy conservation, and emission reduction. This paper first simplifies the target issue of regional power grid through the grid selection method and divides the charging pile area into multiple grids based on the time-load coordinate system to better manage and schedule charging tasks. The study takes into account power level constraints and device-level constraints to ensure that the charging load meets grid limitations and basic user needs. Meanwhile, an optimization function aiming at minimizing the total electricity cost of the charging pile and the peak-to-valley difference of the grid load is proposed. To develop flexible charging strategies and charging plans for different charging models, this paper adopts a genetic algorithm. Through genetic coding and iterative optimization, it derives an electric vehicle charging scheduling scheme that meets grid requirements and user needs. While ensuring efficient operation of charging modules, it achieves balanced loading of modules and dormancy of redundant modules through flexible power allocation, thereby ensuring the long-term stable operation of the charging pile.

Carbon blocks play essential roles in modern industry. However, the preparation of high-quality carbon blocks is still a huge challenge due to the inevitable formation of large numbers of pores and structure defects in carbon blocks caused by the decomposition of pitch. Herein, we report a facile pitch oxygen functionalization approach to improve the coking value, promote polycondensation and cross-linking reactions, and increase the concentration of free radicals, thereby obviously decreasing the number of pores and enhancing the content of smaller size of carbon microcrystallites. As expected, compared with that of pristine pitch, the oxygen functionalized coal tar pitch (CTP-220) demonstrates a dramatically improved oxygen content, coking yield and free radical concentration. When it is employed as binder, the CTP-220 based carbon blocks (CB-CTP220) display a density, flexural and compressive strength, average friction coefficient, and wear rate under current-carrying conditions of 1.66 g/cm3, 68.14 and 157.29 MPa, 0.149, (2.13 +/- 0.2) x 10-2 mm3 & sdot;N-1 & sdot;m-1, respectively, far outperforming that of carbon blocks obtained based on pristine coal tar pitch.

The continuously expanding installed capacity of renewable energy has placed higher demands on the power level of grid-connected converters (GCCs). Consequently, the development of GCCs with higher power, lower cost, and higher performance has become a hotspot in international power electronics research. However, classical GCC technical solutions struggle to meet the trade-offs between multiple performance indicators, including reliability, operating efficiency, power density, power quality, response speed, and cost. To address these issues, an emerging technology involves hybridizing Si and WBG devices in one equipment to combine the high current and high cost-effectiveness of Si inverters with the excellent switching performance of WBG inverters. In this context, this paper reviews in detail the inverters based on hybrid devices (HyDs) and hybrid systems (HySs), which are the two mainstream implementation schemes of Si/WBG hybrid inverters. The latest research on these hybrid inverters is systematically summarized, covering basic principles, hardware design methods, control and optimization strategies, and representative laboratory prototypes. Furthermore, key issues and major challenges in the research and application of Si/WBG hybrid technology are highlighted.

As considerable offshore wind farms (OWFs) are penetrated into power gird. The capacitive effect of long submarine cable causes serious harmonic resonance problems. An improved control strategy for modular multilevel converter (MMC) in OWF is investigated in this paper. The disturbance observer (DOB), which is used to monitor the variation of various system parameters and grid voltage disturbances, is integrated into the control framework of a dual-vector model predictive control (MPC), which aims at the minimum of the enclosed area between the output and the reference current in a single cycle, which ensures the optimal THD of the output current. The DOB compensates the output current and improves the quality of the AC current, which in turn suppresses the harmonic resonance, and enables active damping and enhances the dynamic response performance. A set of simulations have been performed, and the proposed scheme is verified by hardware-in-the-loop experiments by using RT-LAB. The results indicate that the proposed scheme has high current quality with low THD value, high dynamic performance and interference immunity under sudden current change, inductor parameter mismatch and harmonic injection.

Carbon graphite materials play indispensable roles in modern industry. However, ponderous production cycle and high energy consumption are frequently required in the preparation of carbon graphite blocks (CGBs) because it is easy to generate pores and cracks caused by the pyrolysis of raw materials, such as pitch. Recently, while tremendous efforts have been made to optimize the quality of pitch, the contradictory properties, i.e. high plasticity and high residual carbon content, still remain unsolved. Herein, we report an efficient approach to balance those two factors via slightly oxidizing the coal tar pitch/calcined petroleum coke mixture at 195 +/- 5 degrees C, thereby offering a straightforward way to produce high-density CGBs. As expected, the content of light components and olefins in pitch are significantly reduced after oxidation, which not only increases the residual carbon content but also regulates the polymerization behavior. Moreover, being different from previous longterm oxidation, the slight oxidation maintains the initial chemical structure of pitch, e.g. O/C and aromaticity, thus avoiding the appearance of defects in graphite crystals. As a result, the produced carbon block (ATC30) displays an apparent density of 1.61 g/cm3, far outperforming that of without oxidation treatment (ATC-0, 1.51 g/cm3). The graphitized block (ATG-30) delivers dramatically improved apparent density (1.82 g/cm3), crystal size (Lc = 25.04 nm, La = 39.50 nm), structure completeness (average aromatic ring numbers of 1806 in each layer), and mechanical strength when compared with that of ATG-0 counterparts. Impressively, the average friction coefficient under 500 degrees C air atmosphere is determined to be 0.27 for ATG-30 which is approximately one third of that of ATG-0, indicating an excellent wear-resisting performance.

This chapter presents an overview of control and modulation techniques for Z-source converters (ZSCs) used for electric power conversion. ZSCs are categorized into four main categories: DC/DC converters, DC/AC inverters, AC/AC converters, and AC/DC rectifiers. ZSCs are further classified into voltage-fed or current-fed, and non–transformer based or transformer coupled-inductor based. Modulation techniques for traditional three-phase H-bridge topologies (two-level) are classified as sine pulse width modulation and space vector modulation, with several modifications available in the literature. Modulation techniques for three-phase multilevel topologies, matrix topologies, and DC/DC converters with an intermediate H-bridge are also discussed. The impact of modulation strategies on the reliability and harmonics of impedance-source inverters is analyzed. The control strategy of ZSCs is also discussed, with various closed-loop control methods presented in the literature. The chapter concludes that proper modulation and control techniques are necessary to achieve the maximal voltage boost and minimal harmonic distortion, lower semiconductor stress, and minimal number of devices commutation per switching cycle in ZSCs.

In the current source photovoltaic grid-connected system, to prevent the DC-link inductor from incurring an opening circuit fault, it is necessary to include the overlap time in the switching signals. However, current error and serious harmonic distortion in the inverter-side and grid-side currents are generated, which will cause additional losses and reduce the power quality of the grid, so it is important to compensate for the current error caused by the overlap time. In this paper, the relationship between the nonlinear current errors caused by the overlap time and the AC-side voltage is analyzed. Then, the mathematical expression of the low-order harmonics with losses caused by the overlap time is derived. On this basis, a current error compensation method with a discrete filter of AC-side voltage is proposed. Finally, a simulation and experiment are carried out to verify the correctness and effectiveness of the theoretical analysis and compensation scheme presented in this paper. With an overlap time of 3 μs, the THD of the grid-side current decreases from 5.93% to 1.59% after compensation.

This study focuses on the reliability assessment of Press-pack IGBTs, crucial components in power electronics for ensuring stable system operation. Addressing the limitations of existing research, which often neglects the electrothermal coupling effects, we establish a comprehensive model that considers these effects. Through high-precision numerical calculations, we obtain key parameters such as electric field distribution, temperature distribution, and mechanical stress distribution. Experimental validation confirms the model’s accuracy in predicting Press-pack IGBTs’ performance changes and reliability under various operating conditions. This research not only enhances reliability assessment methodologies but also supports optimal design and practical applications of Press-pack IGBTs.