Search Results (96)

The dead-time effect seriously affects the soft-switching performance and operating efficiency of the dual-active-bridge converter, and also causes problems such as reduced duty cycle, distortion of voltage and current waveforms, and narrowed transmission power range. The proposal of the five-degree-of-freedom modulation strategy transforms the working voltage waveforms of the primary and secondary sides as well as the inductor current waveform of the DAB converter from symmetric to asymmetric, while the dead-time issue still persists. Based on the five-degree-of-freedom modulation strategy, this paper analyzes the electrical characteristics of the converter before and after the introduction of dead time, designs switch drive pulses to avoid the dead time, and proposes a dead-time compensation modulation strategy based on five-degree-of-freedom phase shift. The results show that the proposed dead-time compensation control strategy can avoid problems such as voltage and current waveform distortion and reduction in the soft-switching power range caused by dead time, realizing dead-time compensation in the full power range. Experimental measurements show that, for different voltage transmission ratios, the maximum efficiency improvement is approximately 3.8–4% and the current stress is reduced by 2.11% to 3.13% under low-power operating conditions. The maximum efficiency improvement is approximately about 1.4–2.8% and the current stress is reduced by 1.84% to 2.53% under high-power operating conditions. Full article

For power electronic transformer (PET) based Modular Multilevel DC-Link Based T-type Converters (MMDTC) with Double Active Bridges (DABs) (namely DABs-based MMDTC-PET), the sub-module capacitor voltages exhibit relatively large ripples. To reduce the voltage ripple of sub-module capacitors, this paper proposes a novel MMDTC-PET structure that utilizes the Three-Port Active Bridges (TABs) to replace the DABs as the isolation stage (TABs-based MMDTC-PET). When the two full bridges of the TAB on the primary side adopt identical phase-shift modulation, the two sub-module capacitors within the upper and lower arms form a parallel connection. This configuration endows the sub-module capacitors with switched-capacitor characteristics, suppressing voltage ripple in the sub-module capacitors and enabling power ripple flow to the secondary side. Meanwhile, by leveraging the characteristic that the AC power components of the upper and lower arm sub-modules have equal amplitudes but opposite phases, these AC power components are mutually canceled on the secondary side of the TAB. Simulation and experimental results verify the effectiveness of the proposed scheme. Full article

In order to solve the problem that it is difficult to take into account the performance constraints between the core functions of insulation, current flow and arc extinguishing of high-voltage vacuum circuit breakers at the same time, this paper proposes a flexible control strategy for the motor operating mechanism of high-voltage vacuum circuit breakers. The relationship between the rotation angle of the motor and the linear displacement of the moving contact of the circuit breaker is analyzed, and the ideal dynamic curve is planned. The motor drive control device is designed, and the phase-shifted full-bridge circuit is used as the boost converter. The voltage and current double closed-loop sliding mode control strategy is used to simulate and verify the realization of multi-stage and stable boost. The experimental platform is built and the experiment is carried out. The results show that under the voltage conditions of 180 V and 150 V, the control range of closing speed and opening speed is increased by 31.7% and 25.9% respectively, and the speed tracking error is reduced by 51.2%. It is verified that the flexible control strategy can meet the ideal action curve of the operating mechanism, realize the precise control of the opening and closing process and expand the control range. The research provides a theoretical basis for the flexible control strategy of the high-voltage vacuum circuit breaker operating mechanism, and provides new ideas for the intelligent operation technology of power transmission and transformation projects. Full article

Dual-active bridge (DAB) converters have emerged as a preferred topology in electric vehicle charging and energy storage applications, owing to their structurally symmetric configuration and intrinsic galvanic isolation capabilities. However, conventional triple-phase shift (TPS) control strategies face significant challenges in maintaining high efficiency across ultra-wide output voltage and load ranges. To exploit the inherent structural symmetry of the DAB topology, a symmetric optimization strategy based on triple-phase shift (SOS-TPS) is proposed. The method specifically targets the forward buck operating mode, where an optimization framework is established to minimize the root mean square (RMS) current of the inductor, thereby addressing both switching and conduction losses. The formulation explicitly incorporates zero-voltage switching (ZVS) constraints and operating mode conditions. By employing the Karush–Kuhn–Tucker (KKT) conditions in conjunction with the Lagrange multiplier method (LMM), the refined control trajectories corresponding to various power levels are analytically derived, enabling efficient modulation across the entire operating range. In the medium-power region, full-switch ZVS is inherently satisfied. In the low-power operation, full-switch ZVS is achieved by introducing a modulation factor λ, and a selection principle for λ is established. For high-power operation, the strategy transitions to a conventional single-phase shift (SPS) modulation. Furthermore, by exploiting the inherent symmetry of the DAB topology, the proposed method reveals the symmetric property of modulation control. The modulation strategy for the forward boost mode can be efficiently derived through a duty cycle and voltage gain mapping, eliminating the need for re-derivation. To validate the effectiveness of the proposed SOS-TPS strategy, a 2.3 kW experimental prototype was developed. The measured results demonstrate that the method ensures ZVS for all switches under the full load range, supports ultra-wide voltage conversion capability, substantially suppresses RMS current, and achieves a maximum efficiency of 97.3%. Full article

This paper presents the design and implementation of a high-efficiency, full silicon carbide (SiC)-based center-tapped phase-shifted full-bridge (PSFB) converter for NiCd battery charging applications in railway systems. The converter utilizes SiC MOSFET modules on the primary side and SiC diodes on the secondary side, resulting in significant efficiency improvements due to the superior switching characteristics and high-temperature tolerance inherent in SiC devices. A nanocrystalline-cored center-tapped transformer is optimized to minimize voltage stress on the rectifier diodes. Additionally, the use of a nanocrystalline core provides high saturation flux density, low core loss, and excellent permeability, particularly at high frequencies, which significantly enhances system efficiency. The converter also compensates for temperature fluctuations during operation, enabling a wide and adjustable output voltage range according to the temperature differences. A prototype of the 10-kW, 50-kHz PSFB converter, operating with an input voltage range of 700–750 V and output voltage of 77–138 V, was developed and tested both through simulations and experimentally. The converter achieved a maximum efficiency of 97% and demonstrated a high power density of 2.23 kW/L, thereby validating the effectiveness of the proposed design for railway battery charging applications. Full article

A battery charger for solid-state lithium battery packs was developed and implemented. The power stage used a phase-shifted full-bridge converter integrated with a current-doubler rectifier and synchronous rectification. Dual voltage and current control loops were employed to enable constant-voltage and constant-current charging modes. To improve the lifespan of the output filter capacitor, the current-doubler rectifier was adopted to effectively reduce output current ripple. During the initial start-up phase, as the charger transitions from constant-voltage to constant-current output mode, the use of proportional–integral control in the voltage and current loop error amplifiers may cause current overshoot during the step-rising phase, primarily due to the integral action. Therefore, this study incorporated fuzzy control, proportional control, and proportional–integral control strategies into the current-loop error amplifier. This approach effectively reduced the current overshoot during the step-rising phase, preventing the charger from mistakenly triggering the overcurrent protection mode. The analysis and design considerations of the proposed circuit topology and control loop are presented. Experimental results agree with theoretical predictions, thereby confirming the validity of the proposed approach. Full article

The paper presents a study on a phase-shift controlled zero-voltage switching (ZVS) full-bridge DC-DC converter employing synchronous rectification using the LTC3722-1 controller. This analysis aimed to examine the impact of additional commutating inductance on the establishment of ZVS conditions, the precision of switching control, and the dynamic interaction between ZVS performance and varying load conditions. The validity of this approach is achieved by presenting both simulation and experimental results, which illustrate its application in practical applications. Full article

The dual-active-bridge (DAB) converter has emerged as a promising topology for renewable energy applications and microgrid systems due to its high power density and bidirectional energy-transfer capability. Enhancing the overall efficiency and reliability of DAB converters requires the simultaneous realization of zero-voltage switching (ZVS) across all switches and the minimization of current stress over wide load and voltage ranges—two objectives that are often in conflict. Conventional modulation strategies with limited degrees of freedom fail to meet these dual goals effectively. To address this challenge, this paper introduces an enhanced integrated optimization strategy based on triple phase shift (EIOS-TPS). This approach formulates the power transmission requirement as an equality constraint and incorporates ZVS and mode boundary conditions as inequalities, resulting in a comprehensive optimization framework. Optimal phase-shift parameters are obtained using the Karush–Kuhn–Tucker (KKT) conditions. To mitigate zero-current switching (ZCS) under a light load and achieve full-range ZVS with reduced current stress, a modulation factor λ is introduced, enabling a globally optimized control trajectory. An experimental 1176 W prototype is developed to validate the proposed method, which achieves full-range ZVS while maintaining low current stress. In the low-power region, it improves efficiency by up to 2.2% in buck mode and 2.0% in boost mode compared with traditional control strategies, reaching a peak efficiency of 96.5%. Full article

This paper presents a comprehensive summary of recent advances in circuit topologies for piezoelectric energy harvesting, leading to self-powered systems (SPSs), covering the full-bridge rectifier (FBR) and half-bridge rectifier (HBR), AC-DC converters, and maximum power point tracking (MPPT) techniques. These approaches are analyzed with respect to their advantages, limitations, and overall impact on energy harvesting efficiency. Th work explores alternative methods that leverage phase shifting between voltage and current waveform components to enhance conversion performance. Additionally, it provides detailed insights into advanced design strategies, including adaptive power management algorithms, low-power control techniques, and complex impedance matching. The paper also addresses the fundamental principles and challenges of converting mechanical vibrations into electrical energy. Experimental results and performance metrics are reviewed, particularly in relation to hybrid approaches, load impedance, vibration frequency, and power conditioning requirements in energy harvesting systems. This review aims to provide researchers and engineers with a critical understanding of the current state of the art, key challenges, and emerging opportunities in piezoelectric energy harvesting. By examining recent developments, it offers valuable insights into optimizing interface circuit design for the development of efficient and self-sustaining piezoelectric energy harvesting systems. Full article

A full-bridge DC–DC converter with structure exchange is proposed to simulate battery charging based on an electronic load. The full-bridge phase-shift converter (FBPSC) uses an external resonant inductor and phase-shift control on the primary side to realize zero voltage switching (ZVS) above medium load. However, the energy of the resonant inductor is not enough to carry away the energy of the parasitic capacitance on the switch at light load, leading to the inability of ZVS as well as the circulating current problem due to the long duration of the primary-side circulating current. Consequently, in order to conquer such problems mentioned above, the structure exchange, with only the control strategy changed from the phase-shift control to the two-transistor forward control, is presented to increase the light-load efficiency remarkably. Furthermore, the number of inductors is reduced by using the center-tap structure on the secondary side compared to the current-doubler structure. In addition, the synchronous rectifier on the secondary side is used to further improve the overall efficiency of the converter. Full article

To enhance the power output performance of high-power electrolytic plating equipment and improve the dynamic response capability and disturbance rejection ability of the DC-DC converter—a core component in electrolytic plating systems—this study proposes a predictive control strategy for phase-shifted full-bridge converters based on an improved nonlinear disturbance observer. The implementation framework comprises three key technical components: Firstly, a model predictive control (MPC)-based inner-loop controller architecture is constructed to optimize the dynamic response characteristics of the current inner-loop system. Subsequently, an enhanced nonlinear disturbance observer is designed to accurately estimate parameter variations in converter electronic components and external disturbances. Finally, a feedforward compensation module is developed to mitigate the inherent duty cycle loss phenomenon in phase-shifted full-bridge converters. Simulation results demonstrate that the proposed control strategy significantly improves system dynamic performance, achieving a 25% reduction in settling time compared with conventional methods while maintaining robust disturbance rejection capabilities under ±10% voltage fluctuations. This integrated approach effectively addresses the conflicting requirements between dynamic response speed and anti-interference performance in high-power electrochemical process control systems. Full article

This article proposes a fault diagnosis method based on an adaptive sliding mode observer (SMO) for current sensors (CSs) in the charging modules of DC charging piles. Firstly, we establish a model of the phase-shift full-bridge (PSFB) converter with CS faults. Secondly, the fault of the CS is reconstructed through system augmentation and non-singular coordinate transformation. Then, an adaptive SMO is designed to estimate the reconstructed state, and the residual between the actual value of the reconstructed state and the observed value is used as the fault detection variable. Finally, by using norms to design adaptive thresholds and comparing them with fault detection variables, the diagnosis of incipient faults, significant faults, and failure faults in CSs can be achieved. The experimental results verify the effectiveness of the proposed method in this paper; the robustness of the method has been verified under the conditions of DC voltage fluctuations and load fluctuations. Full article

The polar energy router is a key device in the polar clean energy system which converges the output of wind power, photovoltaic units, energy storage units and hydrogen fuel cells through the power electronic power converter to the DC bus, which requires the use of a variety of specifications of DC/DC converters; as a result, the efficiency of the DC/DC converter is directly connected to the efficiency of the polar energy router. This paper presents an enhanced isolated DC/DC converter with a phase-shifted full-bridge topology designed to meet the high-efficiency conversion requirements of polar energy routers. Although soft switching can be realized naturally in phase-shifted full-bridge topology, it also faces challenges, such as the difficulty of realizing soft switching under light load conditions, large circulation losses, a loss of duty cycle and oscillation in the secondary-side voltage. To solve these problems, an improved scheme of the phase-shifted full-bridge converter with an active clamp circuit is proposed in this paper. The scheme realized zero-voltage switch (ZVS) under light load by utilizing clamp capacitor energy. The on-state loss was reduced by zeroing the primary-side current during the circulating phase. This paper provides a detailed description of the topology, working principle and performance characteristics of the improved scheme, and its feasibility has been verified through experiments. Full article

This article proposes a fully soft-switched coupled-inductor-based semi dual-active half-bridge (SDAHB) converter designed for wide voltage range and low power applications. The converter employs a negatively coupled inductor to link a boost-type half-bridge with a semi half-bridge, utilizing a single magnetic component. This approach addresses the issue of low power density often caused by multiple magnetic components, such as leakage inductor and transformer. Additionally, the proposed SDAHB converter includes only three active switches, making it cost-effective. To simplify control implementation, the converter operates under a voltage-matching condition using pulse width modulation plus phase shift (PPS) modulation. This also ensures full-range zero-voltage switching (ZVS) for all switches and zero-current switching (ZCS) for the diode. Finally, an experimental prototype is constructed, and the results confirm the validity of the theoretical analysis and design approach. Full article

Due to the difficulty in achieving a high-power output with a single converter, parallel converters are widely used in high-power applications. However, inconsistency in the output voltage feedback coefficients of individual converters and the associated dispersion in parallel systems often lead to unbalanced current sharing during transient processes, such as load disturbances. This imbalance can result in certain converters being overloaded during transients, leading to premature shutdown. Subsequently, the load on the remaining converters increases, further aggravating the imbalance and triggering additional shutdowns in a domino effect, which may, ultimately, cause the entire parallel converter system to shut down. To address this issue, this study focuses on parallel phase-shift full-bridge systems, analyzing the intrinsic mechanism by which feedback coefficient dispersion affects transient current sharing. A droop control strategy with improved transient virtual impedance is proposed to enhance the current sharing during transients. A simulation and experimental results demonstrate that the proposed strategy significantly improves current sharing during transient processes, effectively enhancing the dynamic performance and reliability of the system. Full article