查看更多>>摘要：Efficient assessment of battery degradation is important to effectively utilize and maintain battery management systems.This study introduces an innovative residual convolutional network(RCN)-gated recurrent unit(GRU)model to accurately assess health of lithium-ion batteries on multiple time scales.The model employs a soft parameter-sharing mechanism to identify both short-and long-term degradation ipatterns.The continuouslsy looped Q(V),T(V),dQ/dV,and dT/dV are extracted to form a four-channel image,from which the RCN can automatically extract the features and the GRU can capture the temporal features.By designing a soft parameter-sharing mechanism,the model can seamlessly predict the capacity and remaining useful life(RUL)on a dual time scale.The proposed method is validated on a large MIT-Stanford dataset comprising 124 cells,showing a high accuracy in terms of mean absolute errors of 0.004 77 for capacity and 83 for RUL.Furthermore,studying the partial voltage fragment reveals the promising performance of the proposed method across various voltage ranges.Specifically,in the partial voltage segment of 2.8-3.2 V,root mean square errors of 0.010 7 for capacity and 140 for RUL are achieved.
查看更多>>摘要：Isolation-dependent applications require a transformer with high efficiency,low magnetizing current,and anti-DC bias capability.The kilohertz planar negative magnetic reluctance structure is used to achieve this target with its magnetic-frequency variation property,which reduces the magnetic reluctance of the fundamental component.However,this design cannot be applied to low-frequency transformers owing to the high loss caused by its limited self-inductance and quality factor.To solve this problem,a pole-wrapped negative equivalent magnetic reluctance(PNEMR)structure is presented.The proposed design employed a copper-based PNEMR structure wrapped around the magnetic poles to enhance the fundamental flux and suppress the DC component of flux.Accordingly,the magnetizing current is reduced,and the isolation transformer is less susceptible to the DC bias.The proposed design can simultaneously improve the anti-DC magnetic bias capability,efficiency,and power factor of the transformers.To verify the effectiveness of the proposed design,a 10 kW C-core PNEMR structure-based transformer for isolation-dependent applications was constructed and compared to the generalized structures and transformers with planar negative magnetic reluctance structures.Results indicate that the PNEMR-based transformer can enhance the efficiency and power factor from 96.1％and 0.87 to 96.6％and 0.93,respectively,under full load conditions.
查看更多>>摘要：Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(SVPWM)is a more popular scheme,but conventional 4L SVPWM cannot achieve the voltage balancing control of DC-link capacitors,is complex to implement,and requires costly computation.A hybrid modulation method with capacitor voltage-balancing control for 4L NPC converters is proposed.The proposed method is achieved using three-level(3L)SVPWM and two-level(2L)carrier-based pulse-width modulation(CPWM)based on the concept of"4L=3L+2L".Thus,it can be easily implemented on a digital chip because the modulation process is nearly identical to that of 3L SVPWM without the more cumbersome 4L SVPWM algorithm.Meanwhile,any proven optimization scheme of 3L SVPWM can be directly applied to the proposed method to further improve performance.Simulation and experimental results for a 4L active NPC converter demonstrate the effectiveness of the proposed method.
查看更多>>摘要：Conventional sliding-mode observer(SMO)-based grid-voltage observation methods often require a low-pass filter(LPF)to remove high-frequency sliding-mode noise.However,a complicated phase-and amplitude-compensation method,which is highly sensitive to the DC-offset,is required.A frequency-adaptive dual second-order generalized integrator(SOGI)can be used to replace the LPF,eliminating the compensation link and the effects of the DC-offset;however,strong coupling is introduced between the front-end SOGI block and back-end phase-locked loop(PLL)block,thereby reducing the dynamic performance.To solve this problem,this study proposes an SMO-based grid-voltage observation method with a frequency-fixed dual SOGI and cross-compensated PLL that can eliminate the frequency coupling between the front-end SOGI block and back-end PLL blocks,thereby increasing its dynamic performance.In this study,the phase and amplitude are compensated simultaneously using the proposed cross-compensation method,achieving an accurate observation of the grid voltage under off-nominal frequencies.An analysis of the small-signal model theoretically verified that the proposed method has good dynamic performance.Finally,the superiority of the proposed method is verified through comparative experiments.
查看更多>>摘要：In this study,a comprehensive approach is presented for the sizing and management of hybrid renewable energy systems(HRESs)that incorporate a variety of energy sources,while emphasizing the role of artificial neural networks(ANNs)in system management.For optimal sizing of an HRES,the monthly average method wherein historical weather data are used to calculate the monthly averages of solar irradiance and wind speed,offering a well-balanced strategy for system sizing.This ensures that the HRES is appropriately scaled to meet the actual energy requirements of the specified location,avoiding the pitfalls of over-and under-sizing,and thereby enhancing the operational efficiency.Furthermore,the study details a cutting-edge strategy that employs ANNs for managing the inherent complexities of HRESs.It elaborates on the design,modeling,and control strategies for the HRES components by utilizing Matlab/Simulink for implementation.The findings demonstrate the proficiency of the ANN-based power manager in determining the operational modes guided by a specifically designed flowchart.By integrating ANN-driven energy management strategies into an HRES,the proposed approach marks a significant advancement in system adaptability,precision control,and efficiency,thereby maximizing the effective utilization of renewable resources.
查看更多>>摘要：Droop-controlled voltage-source converters(VSCs)can provide frequency and voltage support to power grids.However,during a grid fault,VSCs may experience transient instability,which can be significantly affected by both the control parameters and fault conditions.This mechanism has not been fully elucidated in previous studies.In particular,grid-voltage faults are commonly accompanied by a grid voltage phase-angle jump(VPAJ),which is typically ignored in the evaluation of the transient stability of VSCs.To address this issue,this study comprehensively assesses the impact of the VPAJ and key control parameters on the transient characteristics of VSCs.Furthermore,the critical clearing angle and critical clearing time are quantitatively calculated to define the transient stability boundary.In addition,a transient stability-enhancement control method that considers the transient stability constraints is proposed.Finally,simulations and experimental tests are conducted to validate both the theoretical analysis and proposed method.
查看更多>>摘要：A dynamic reconfiguration method for photovoltaic(PV)arrays based on an improved dung beetle algorithm(IDBO)to address the issue of PV array mismatch loss caused by partial shading conditions(PSCs)is proposed.To establish the output power-current(P-I)segmentation function for the total-cross-tied(TCT)PV array and the constraint function for the electrical switches,the IDBO algorithm was used to optimize both the P-1 segmentation function and the electrical switch constraint function.IDBO is compared with algorithm-free reconfiguration and five other heuristic algorithms using two evaluation criteria:mismatch loss and power enhancement percentage,across six shading scenarios for 6x6 PV arrays.The irradiation distribution of PV arrays reconfigured by IDBO is also presented.The results show that IDBO effectively increases the output power of PV arrays and reduces mismatch loss.The output PV curves tend to exhibit a single peak,and the reconstruction results are superior to those obtained with the other methods.
查看更多>>摘要：Permanent magnet synchronous motors(PMSMs)driven by voltage source inverters(VSIs)with pulse width modulation(PWM)are widely used.Given the impact of acoustic noise on the environment and human ears,the comfort level of the high-frequency vibration noise emitted by PMSMs has become an important factor.This study introduces the current mainstream high-frequency vibration noise suppression strategies for PMSMs by reducing the high-frequency current harmonics of stator windings,including spread spectrum technology,vector position exchange technology,and interleaved parallel technology.Furthermore,this study analyzed and compared the advantages and disadvantages of various suppression strategies.
查看更多>>摘要：Energy shortages have hindered global economic development.By utilizing waste as a substrate for microbial fermentation,hydrogen production can transform waste into a valuable resource,significantly reducing the cost of hydrogen production and addressing a significant hurdle in achieving large-scale production of microbial hydrogen.This approach has significant potential for future hydrogen-production applications.Two-stage indirect photohydrolysis has recently emerged as a promising and efficient method for hydrogen production using cyanobacteria and green algae.However,this method cannot be directly applied to organic wastewater for hydrogen production.In contrast,dark fermentation by bacteria,particularly ethanol-type fermentation,is highly efficient for producing hydrogen.Therefore,the combination of the indirect photohydrolysis of algae and dark fermentation by bacteria is expected to significantly enhance the hydrogen-production capacity of organic wastewater,laying the groundwork for future large-scale microbial hydrogen production.This study reviews the main types and technical principles of microbial hydrogen production from waste,available waste types,research progress in the microbial hydrogen-production process,strategies to improve the hydrogen-production rate,and challenges faced during industrialization.Future research directions for microbial-waste hydrogen production are also proposed.The aim of this study is to provide a valuable reference for large-scale biological hydrogen-production research.
查看更多>>摘要：With the increasing complexity of electrical vehicles(EVs),the wide-speed-range high-efficiency characteristics of EV drive motors are in strict demand.In this study,the variable magnetic flux effect is introduced into a permanent magnet(PM)motor,and a variable magnetic flux permanent magnetic(VMF-PM)motor is proposed.First,the flux is adjusted flexibly to synchronously broaden the speed regulation range and high-efficiency region.Subsequently,an efficiency analytical model is developed considering the motor speed,current,and flux variations.It is indicated that by the purposeful design of the variable flux leakage topology,the efficiency under high speed can be improved based on a theoretical investigation of the high-efficiency boundary.In addition,based on finite element analysis,the performances before and after optimization of the key parameters of the VMF-PM motor are investigated,including the flux variable characteristics and efficiency characteristics.Finally,a prototype motor is built and tested.Both theoretical analysis and experimental results confirm that based on the assistance of the variable magnetic flux effect,the motor high-efficiency region is broadened effectively,providing a potential research path for designing a wide-speed-range high-efficiency motor.
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