特刊主编寄语：电力电子在未来可再生能源和Power-to-X系统中的作用

Decarbonization of major energy-consuming sectors is a top priority of the 2015 Paris Agreement and the Climate Change 2023 report from the Intergovernmental Panel on Climate Change (IPCC). This has significantly challenged today’s energy systems with the development of long-term sustainable energy production and storage. Perhaps one of the most promising strategies for addressing this challenge is the implementation of hydrogen and power-to-X (P2X) solutions, in which renewables can be heavily utilized and new ways of storing and transporting this green energy can be followed. This term, i.e., P2X, is a collective term for conversion technologies that turn electricity into carbon-neutral synthetic fuels, such as hydrogen, synthetic natural gas, or chemicals. In this context, power electronics is expected to play a key role in enhancing the performance and reducing the final product cost of such systems, where different systems are expected to be integrated together, e.g., different types of renewables to feed a cluster of electrolyzers for hydrogen production, with potentially a grid connection, where grid support might be a possible option as well. Moreover, electrolyzers and fuel cells, as key elements in such P2X systems, are low-voltage high-power elements, whose voltage varies significantly under different loading conditions and over lifetime. Therefore, the utilized power converters must ensure high performance over a wide range of operating conditions from beginning to end of life while meeting the requirements on the source or load side. We have received 33 submissions from various countries/regions to this special issue of JESTPE, and after peer-reviewing, 13 of the submissions were finally accepted and included. The accepted papers can be categorized into four sections under the corresponding topic: 1) power electronic converters and their modulation; 2) control of power converters in dc and ac microgrids; 3) analysis and modeling of power converters; and 4) measurements and protection. A. Power Electronics Converters and Their Modulation This topic includes three papers that discuss different power electronics topologies that can be utilized in various renewables and P2X systems and explore different modulation schemes for enhanced overall system performance. In [A1], a discontinuous modulation scheme is studied with a differentially structured flyback inverter to improve the inverter performance in terms of efficiency, device ratings, and harmonics. In [A2], a closed-loop control architecture with a hybrid modulation technique is presented for power electronic transformers (PETs) integrating medium-voltage ac systems with low-voltage dc or ac systems to improve the current THD and the system performance under no-load conditions. Finally, a hybrid transformer architecture, featuring the partial power processing capability, multiplexing of the converter unit, and coordination with AC grids, is proposed [A3] to enhance the overall system performance under a wide range of operations and to increase the overall conversion efficiency. B. Control of Power Electronic Converters in DC and AC Microgrids Converter and overall system control and coordination are vital in renewables and P2X systems to increase the overall system performance and reliability. Under this topic, four papers have explored different challenges and introduced improved or novel control strategies. In [A4], a novel fourth-order generalized integrator-based harmonic decoupling network is introduced for extracting load current and grid voltage sequence components in a distribution static compensator (DSTATCOM) that can be utilized in ac microgrids. On the other hand, Hu et al. [A5] present an inertia evaluation and optimal design of permanent magnet synchronous generator (PMSG)-based wind turbines to avoid inaccurate inertia evaluation and unsatisfactory design of control parameters. Moreover, Si et al. [A6] have studied the transient angle and/or voltage instability of grid-forming converters with typical reactive power control schemes, where comparative assessments have been presented. Finally, a sector-wise modified droop coefficient adjustment control is proposed in [A7], which ensures enhanced loading operation of individual converters while maintaining the voltage regulation constraints and enhancing the overall system performance. C. Analysis and Modeling of Power Converters Under this topic, two papers have been included that analyze and model power converters used in different renewables and P2X systems. Ye et al. [A8] explain the comprehensive modeling procedure of a three-port dc-dc converter with three series resonant windings, where the strategies of harmonic approximation, extended describing function method, and state variable reduction are used to properly simplify the original nonlinear high-order equations. On the other hand, the operation of a practical current source fed phase shift-controlled semi-active rectifier (SAR) is revisited taking into account output capacitances of switching devices in order to derive lower and upper bounds of attainable output dc current and phase shift angle, where measurement and computational delay, imposed by digital implementation, are also considered for accurate prediction of practical system behavior. D. Measurements and Protection Finally, it is of paramount importance to maintain a reliable operation of a P2X system, where measurements, communication, and protection play a key role. This topic includes four papers, where Abramovitz et al. [A10] provide a methodology for deriving a family of output characteristics for a passive magnetic energy harvester (MEH) clamped on a sinusoidal current-carrying conductor and demonstrate that MEH characteristics depend on primary current magnitude and frequency as well as on load voltage, where such an MEH can be utilized in sensing equipment as an application. In [A11], the practical implementation of energy-information integrated transmission (EIT) technology is discussed for ac systems, where a model of the ac transmission channel that includes power electronic converters, power lines, and loads is presented. On the other hand, Pogulaguntla et al. [A12] proposed a novel single-branch solid-state circuit breaker (SB-SSCB) that uses air-core coupled coils to commutate an SCR in the main conduction path, where the modularity is achieved by extending the SB-SSCB to a two-branch design in order to handle higher currents with reduced component count. Finally, Dsa et al. [A13] introduce a compact, resettable, and bidirectional solid-state dc disconnector (SSD) as a solution to overcome slow response times, degradation with fault occurrences, and the need for regular maintenance and replacement in conventional protection schemes. The editorial team hopes that this JESTPE special issue will provide readers with new inspiration and will encourage them to make further progress on the topic of renewables and P2X systems. We believe that in the long term, extensive research in this challenging field will significantly facilitate innovation forward and accelerate industrial utilizations. We would like to thank the authors for their valuable contributions and the reviewers who have voluntarily provided constructive and timely feedback. Moreover, we want to thank the following guest associate editors for their help with this special issue (in alphabetical order): Ayman El-Refaie (University of Marquette, USA) Haoran Zhao (University of Shandong, China) Hirohisa Aki (University Tsukuba, Japan) Hong Li (University of Beijing Jiaotong, China) Mahshid Amirabadi (Northeastern University, USA) Paolo Mattavelli (University of Padova, Italy) Pooya Davari (Aalborg University, Denmark) Qianwen Xu (KTH, Sweden) Thiago Batista Soeiro (University of Twenty, Netherlands) Tommaso Caldognetto (University of Padova, Italy) Xiongfei Wang (KTH, Sweden) Yam Siwakoti (University of Technology Sydney, Australia) Yonghao Gui (ORNL, USA) Yongheng Yang (University of Zhejiang, China) Zian Qin (University of Delft, The Netherlands) Finally, we would like to express our gratitude to the Editor-in-Chief, Fernando Briz, for his guidance during the review process and assistance with the preparation of this special issue. Appendix: Related Articles A. I. M. Ali et al., “Discontinuous modulation technique for isolated three-phase grid-connected flyback inverter with selective harmonic compensation for PV and fuel cell systems,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2849–2863, Jun. 2025, doi: 10.1109/jestpe.2024.3492734. H. Patel, K. Hatua, and S. Bhattacharya, “Hybrid modulation technique of MV grid connected cascaded H-Bridge based power electronic transformer technology,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2864–2878, Jun. 2025, doi: 10.1109/jestpe.2025.3539530. H. Guo, Q. Xiong, C. Li, and M. Zhou, “The hybrid transformer with battery storage integration for electrical vehicle ultra-fast charging,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2879–2891, Jun. 2025, doi: 10.1109/jestpe.2024.3457774. G. Modi, B. Singh, S. Pradhan, and H. Parveen, “A novel control strategy to integrate DSTATCOM functionalities in a grid connected AC microgrid, featuring SPV-BES and SyRG-wind based DGs,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2892–2904, Jun. 2025, doi: 10.1109/jestpe.2025.3554571. B. Hu, D. Zhu, J. Hu, R. Liu, X. Zou, and Y. Kang, “Inertia evaluation and optimal design for PMSG-based wind turbines with df/dt control,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2905–2916, Jun. 2025, doi: 10.1109/jestpe.2024.3496659. W. Si, J. Fang, X. Chen, T. Xu, and S. M. Goetz, “Transient angle and voltage stability of grid-forming converters with typical reactive power control schemes,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2917–2927, Jun. 2025, doi: 10.1109/jestpe.2024.3477492. M. Ramana, S. B. Santra, D. Chatterjee, and Y. P. Siwakoti, “Sector wise modified droop control to improve voltage regulation and current sharing in parallel boost converter interfaced DC microgrid,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2928–2943, Jun. 2025, doi: 10.1109/jestpe.2024.3486554. Z. Ye, C. Li, Z. Zheng, W. Shu, X. Weng, and J. Wang, “Modeling and control for the DC–DC three-port series resonant converter in Power-to-X application,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2944–2955, Jun. 2025, doi: 10.1109/jestpe.2025.3536500. A. Vulfovich and A. Kuperman, “Practical phase shift angle bounds in current fed digitally controlled ZVS semi-active rectifiers,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2956–2965, Jun. 2025, doi: 10.1109/jestpe.2024.3496702. A. Abramovitz, M. Shvartsas, G. I. Orfanoudakis, and A. Kuperman, “Output characteristics of passive magnetic energy harvester feeding a constant-voltage-type load,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2966–2974, Jun. 2025, doi: 10.1109/jestpe.2024.3476284. L. Zheng et al., “Research on channel characteristics of energy-information integrated AC transmission system,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2975–2987, Jun. 2025, doi: 10.1109/jestpe.2024.3483837. A. Pogulaguntla et al., “Air-core coupled inductor based modular solid-state circuit breaker with reduced components for DC buildings,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 2988–2999, Jun. 2025, doi: 10.1109/jestpe.2024.3485735. D. Dsa, A. Chinnusamy, S. N. Banavath, and E. L. Carvalho, “Implementation of protection features for a modular bidirectional solid-state battery disconnector,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 13, no. 3, pp. 3000–3012, Jun. 2025, doi: 10.1109/jestpe.2024.3502157.