Search Results (113)

Railway turnouts are highly susceptible to snow and ice accumulation during winter, which can cause malfunctions, resulting in train delays or, in extreme cases, derailments with potential casualties. To mitigate these risks, resistive heating (RH) systems using nichrome wires have traditionally been employed. However, these systems suffer from slow heat transfer and high power consumption. To address these limitations, this article proposes an induction heating (IH) system designed for rapid thermal response and improved electrical and thermal efficiency. The proposed system comprises a power conversion unit featuring a boost power factor correction (PFC) stage and a high-frequency resonant inverter, along with an improved IH coil. An experiment in real snowfall demonstrates the IH system’s fast heat-up capability, effective snow cover removal, and enhanced energy efficiency compared to conventional methods. Full article

With the booming development of the 5G market in recent years, super-high frequency (SHF) resonators will play an increasingly critical role in 5G and future communication systems. Facing the growing market demand for miniaturized, high-bandwidth, and low insertion loss filters, the design of SHF resonators and filters with a high effective electromechanical coupling coefficient (K²_eff) and quality factor, low insertion loss, high passband flatness, strong out-of-band rejection, and high power handling capacity has placed high demands on piezoelectric material preparation, process optimization, and resonator design. The polarity-inverted Al(Sc)N multilayer substrate has become one of the key solutions for SHF resonators. This review provides a comprehensive overview of the recent advances in SHF Al(Sc)N bulk acoustic wave (BAW) resonators. It systematically discusses the device design methodologies, structural configurations, and material synthesis techniques for high-quality Al(Sc)N thin films. Particular emphasis is placed on the underlying mechanisms and engineering strategies for polarity control in Al(Sc)N-based periodically poled multilayer structures. The progress in periodically poled piezoelectric film (P3F) BAW resonators is also examined, with special attention to their ability to significantly boost the operating frequency of BAW devices without reducing the thickness of the piezoelectric layer, while maintaining a high K²_eff. Finally, the review outlines current challenges and future directions for achieving a higher quality factor (Q), improved frequency scalability, and greater integration compatibility in SHF acoustic devices, paving the way for next-generation radio frequency (RF) front-end technologies in 5G/6G and beyond. Full article

A class E inverter has presented wide application prospects in inductive wireless power transfer (WPT) systems due to its significant advantages such as high operation frequency, high power density, and low cost. However, its semiconductor power device is subjected to voltage stress several times higher than the input DC voltage, which inevitably increases the risk of overvoltage failure and limits the system power level. In this manuscript, an inductive WPT system with the pull–push class EF2 inverter is proposed to significantly decrease the voltage stress and ensure soft switching characteristic. The working principle and time-domain waveforms of the pull–push class EF2 inverter are analyzed. Moreover, the differential equations and mathematical model of the resonant parameters are investigated. Compared with the conventional class E inverter, the output power of the proposed inductive WPT system is doubled under the same input voltage. A 100 W system prototype is designed at the operating frequency of 6.78 MHz (according to the A4WP standard) and its experimental results demonstrate the effectiveness and feasibility of the analysis. Full article

The modernization of agriculture can help humanity address major challenges such as population growth, climate change, and labor shortages. Semi-autonomous agricultural robots offer clear advantages in automating tasks and improving efficiency. However, in open-field conditions, their autonomy is limited by the size and weight of onboard batteries. Wireless charging is a promising solution to overcome this limitation. This work proposes a methodology for the design, modeling, and experimental validation of a wireless power transfer (WPT) system for battery recharging of agricultural robots. A brief review of WPT technologies is provided, followed by key design considerations, co-simulation, and testing results. The proposed WPT system uses a resonant inductive power transfer topology with series–series (SS) compensation, a high-frequency inverter (85 kHz), and optimized spiral planar coils, enabling medium-range operation under agricultural conditions. The main contribution lies in the first experimental assessment of WPT performance under real agricultural environmental factors such as soil moisture and water presence, combined with electromagnetic safety evaluation and robust component selection for harsh conditions. Results highlight both the potential and limitations of this approach, demonstrating its feasibility and paving the way for future integration with intelligent alignment and adaptive control strategies. Full article

The instantaneous AC-side output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency, inducing second harmonic current (SHC) in the front-end DC–DC converter. While conventional SHC mitigation methods mainly focus on controller optimization for PWM-controlled DC–DC converters, LLC resonant converters, which have been widely adopted in two-stage single-phase inverters for high efficiency and soft-switching characteristics, lack tailored solutions due to frequency modulation complexities. To address this gap, this paper first analyzes the propagation mechanism of the SHC in terms of converter output impedance. Then, by simultaneously lowering the open-loop gain and increasing the output impedance of the DC–DC converter at 2f_N, this paper proposes a hybrid SHC mitigation strategy that achieves low SHC and fast dynamic performance for frequency-modulated LLC converters. Finally, a 28 V DC to 220 V/50 Hz AC inverter was developed, and the experimental results verified the effectiveness of the proposed control strategy. Full article

A self-diplexing, full-mode, substrate-integrated waveguide (SIW) rectangular cavity-backed antenna based on an inverted Z-shaped radiating slot with filtering characteristics is investigated in this work. The proposed design allows for individual control through the loading of four different slots, namely, a combination of horizontal and diagonal slots, called inverted Z-shaped slots. The two diagonal slots make 45° angles between them, and this flexible rotation gives the design flexibility regarding control of the bands. By combining these slots into a modified inverted Z-shaped slot, a SIW rectangular cavity is configured and energized with two separate 50 Ω microstrip feed lines to resonate at two different frequencies—11.63 GHz and 13.27 GHz—and TE₂₁₀ and TE₂₂₀ modes are obtained for X- and Ku-band wireless purposes. In an experimental analysis, reflection coefficients of S₁₁ < −10 dB were noted for both operating frequencies of 7.4% (11.23–12.09 GHz) and 3.0% (13.15–13.55 GHz), respectively. The average gain of the proposed antenna design in the two different operating conditions is 6.14 and 6.16 dBi, respectively. In addition, the proposed self-diplexing antenna attained high isolation, greater than 28 dB between both operating channels, and showed overall measured efficiency of 87.32%. Moreover, it features a single-layer structure, operates in dual bands, provides broadside linear polarization, and exhibits filtering capabilities. Full article

The quality of a grid-injected current in LCL-type grid-connected inverters (GCI) degrades under ultra-weak grid conditions, posing serious challenges to the stability of the GCI system. For this purpose, the sliding mode control (SMC) approach has been utilized to integrate DC energy seamlessly into the grid. The control performance of a GCI equipped with an LCL filter is greatly reduced when it is operating in a power grid with varying impedance and fluctuating grid voltages, which may result in poor current quality and possible instability in the system. A non-singular double integral terminal sliding mode (DIT-SMC) control is presented in this paper for a three-phase GCI with an LCL filter. The proposed method is presented in the α, β frame of reference without adopting an active or passive damping approach, reducing the computational burden. MATLAB/Simulink Version R2023b is leveraged to simulate the mathematical model of the proposed control system. The capability of the DIT-SMC method is validated through the OPAL-RT hardware-in-loop (HIL) platform. The effectiveness of the proposed method is first compared with SMC and integral terminal SMC, and then the DIT-SMC method is rigorously analyzed under resonance frequency events, grid impedance variation, and grid voltage distortions. It is demonstrated by the experimental results that the proposed control is highly effective in delivering a high-quality current into the grid, in spite of the simultaneous occurrence of power grid impedance variations in 6 mH and large voltage distortions. Full article

Multi-channel LED drivers are crucial for high-power lighting applications. Maintaining a constant average forward current is essential for stable LED luminous intensity, necessitating drivers capable of consistent current delivery across wide operating ranges. Meanwhile, achieving precise current sharing among channels without incurring high costs and system complexity is a significant challenge. Leveraging the constant-current characteristics of the LCL-T network, this paper presents a multi-channel DC/DC LED driver comprising a full-bridge inverter, a transformer, and a passive resonant rectifier. The driver generates a high-frequency AC bus with series-connected diode rectifiers, a structure that guarantees excellent current sharing among all output channels using only a single control loop. Fully considering the impact of higher harmonics, this paper derives an exact solution for the output current. A step-by-step parameter design methodology ensures soft switching and enhanced switch utilization. Finally, experimental verification was conducted using a prototype with five channels and 200 W, confirming the correctness and accuracy of the theoretical analysis. The experimental results showed that within a wide input voltage range of 380 V to 420 V, the driver was able to provide a stable current of 700 mA to each channel, and the system could achieve a peak efficiency of up to 94.4%. Full article

Low-Voltage DC-DC converters (LDCs) in electric vehicles require high power density and high efficiency operation over the wide range of load and input voltage variations. This paper introduces a novel topology which combines three 1 MHz half-bridge (HB) LLC resonant converters and an inverting buck–boost (IBB) converter to adjust the output voltage without frequency modulation. The switching frequency of the proposed converter is fixed at 1 MHz to achieve a constant frequency operation for the resonant converter. In the proposed topology, Gallium Nitride (GaN) devices and planar transformers are employed to optimize the converter operation at high frequency. A 1-MHz/1.8 kW-400/14 V prototype converter is built to verify the feasibility and the validity of the proposed LDC topology. Full article

Reducing mutual coupling between radiation elements of compact MIMO vehicle antennas is of fundamental importance to achieve simultaneous high capacity and miniaturization. In this work, we propose a commercial vehicle MIMO antenna composed of two inverted-F elements that achieves high isolation of mutual coupling through the incorporation of the electric split ring resonator (SRR). The working mode and frequency band of the SRR are rationally selected based on characteristic mode analysis (CMA). Experimental results validate high isolation below −20 dB across a broadband frequency range from 1.7 GHz to 2.7 GHz, achieving a relative bandwidth of 45.4%, with a maximum reduction of 15 dB of the S21 parameter. Additionally, the MIMO antenna maintains stable performance in both return loss and radiation characteristics, with minimal degradation in gain and radiation pattern. This work provides a compact and bandwidth-enhanced solution for vehicular communication systems. Full article

Compared with the line-frequency transformer (LFT), the emerging power electronic transformers (PETs) have gained wide concerns due to the significant merits of higher power density, higher reliability, more flexibility, and multiple functions. However, the need for bulky energy storage elements, multi-stage power conversion and reduced conversion efficiency, and the intrinsic twice-frequency pulsating power issue are the main disadvantages of the conventional single-phase PETs. To overcome the above shortcomings of conventional single-phase PETs, this paper develops a matrix-type single-phase AC-AC PET without bulky energy storage elements. The proposed PET consists of a line-frequency commutated rectifier, a half-bridge LLC resonant converter with a fixed switching frequency, a boost converter, and a line-frequency commutated inverter. The LLC operates efficiently with unity voltage gain and acts as a high-frequency isolated DC transformer (DCX). The boost converter provides AC output voltage regulation function and the line-frequency commutated inverter unfolds the output voltage of the boost converter to generate the sinusoidal AC output voltage. As a result, high power density, reduced power conversion stages, direct AC-AC power conversion without twice-frequency pulsating power, high conversion efficiency, and high reliability are achieved. The experimental results on a 1kW PET prototype show that sinusoidal input current and output voltage, ZVS of the LLC stage, and output voltage regulation capability are realized. The experimental results verify the correctness and feasibility of the presented methods. Full article

With the development of the new power system with a high proportion of new energy and a high proportion of power electronic equipment, various problems caused by high-frequency oscillation will seriously affect the daily normal operation of the power system. For the existing active oscillatory suppression strategies, the impedance characteristics of other frequency bands will be affected, which may cause new oscillation problems in other frequency bands, namely the negative effect of oscillatory suppression strategy. In response to such phenomena, we conducted research on the mechanism of negative effects and optimize the control strategies accordingly. First, an analysis model of the grid-connected inverter was established. The concept of the damping factor was proposed based on the relationship between passive damping and active damping. The feasibility of the oscillation suppression mechanism based on the damping factor was demonstrated, and the negative effect mechanism of the oscillation suppression strategy was clarified. Secondly, a control strategy based on the superposition of active damping was proposed, which not only solved the negative effect of the oscillation suppression strategy but also avoided the shift of the inherent resonance point. Finally, the theory was verified based on the MATLAB R2022a/Simulink simulation platform. Full article

The main contribution of this paper is to show the analysis and design of a resonant converter which was designed to operate in the transient stage and with underdamped response, where the resonant network stage has a frequency equal to “n” times the frequency of the switching stage (f_sw) “f_o = nf_sw”. The main advantage of this design methodology is to be able to operate the converter with frequencies higher than 1 MHz in the resonant network stage, without obtaining high levels of losses in the inverse stage. To validate this design methodology, a full bridge resonant converter acting as a frequency multiplier was implemented for a low power wireless power transmission application. For the experimental tests, a base frequency of 300 kHz was decided in the inverting stage, with a frequency multiplication of n = 3, 5, 7 in the resonant network stage (900 kHz, 1.5 MHz, 2.1 MHz) for an output power of 12 watts. Experimental tests proved the operation of the converter acting as a multiplier, where it was possible to reduce losses in the inverter stage, achieving efficiencies of up to 93% in the switching stage with frequencies higher than 1 MHz. Full article

This paper reviews the current state of research on half-bridge (HB) inverters used in induction heating power supplies, emphasizing their topological structures, output power control methods, and switching strategies. The study explores various control techniques to regulate low power levels in a series resonant inverter (SRI) configured with an HB structure for induction heating applications. Pulse frequency modulation (PFM) is commonly employed to regulate standard power levels by adjusting the operating frequency relative to the resonant frequency. As the operating frequency increases beyond resonance, the output power decreases. However, in certain scenarios, achieving low power levels necessitates high frequencies, which introduces significant control challenges. To address these issues, it is crucial to develop alternative approaches that ensure efficient power reduction, without compromising system performance. This work evaluates and compares multiple solutions tailored for a high-frequency induction heating system delivering 18 kW at an operating frequency of approximately 100 kHz. The study places particular emphasis on optimizing key component sizing and analyzing inverter losses to enhance overall system efficiency and reliability. Full article

The impedance of the harmonic plane in a dual three-phase permanent magnet synchronous motor (DTP-PMSM) is very low, meaning that even small harmonic voltages can induce significant harmonic currents, particularly at the fifth and seventh harmonic frequencies. These harmonic currents can severely degrade system performance and increase losses. To address this issue, the mechanism of harmonic current generation due to non-sinusoidal back electromotive force (EMF) and inverter nonlinearity is first analyzed. Then, to overcome the challenge of excessive controllers in traditional harmonic suppression strategies, a rotational coordinate transformation of the harmonic plane current is employed, which unifies the controllers and reduces their number. Since traditional proportional-integral resonant (PIR) controllers are ineffective at a high-speed region, an improved PIR controller for the harmonic plane is proposed. This controller incorporates digital delay compensation, phase compensation, and discretization correction to minimize the deviation between the discretized resonant frequency and the actual frequency. These enhancements enable harmonic suppression across the entire speed range and under varying load conditions, significantly reducing harmonic currents. Finally, the proposed harmonic current suppression strategy is experimentally validated. Full article