To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power incr...To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power increases current stress of devices and decreases efficiency,especially under light load conditions.Several modulation methods have been proposed to overcome the problem.They can reduce or eliminate either input or output side circulating power.In contrast,S-PWM not only eliminates both sides circulating power and reduces current stress,but also achieves zero-current-switching(ZCS)turn-on for all switches and ZCS turn-off for most across the full power range.No auxiliary or snubber circuits are increased.In addition,the control can be simplified so the transmitted power is related to only one variable.The S-PWM has four cases under different gain and power conditions.The detailed operation principle and modes of DAB under S-PWM are analyzed in the paper.In addition,four modulations in literature are discussed,and corresponding comparative analyses with S-PWM are given.Finally,a laboratory prototype is built to verify advantages and effectiveness of the proposed modulation.展开更多
In the converter steelmaking process,the flow dynamics is closely related to the refractory lining structure of the bath,such as hearth height-to-diameter(H/D)ratio and lining erosion at different campaign stages.The ...In the converter steelmaking process,the flow dynamics is closely related to the refractory lining structure of the bath,such as hearth height-to-diameter(H/D)ratio and lining erosion at different campaign stages.The step of pre-processing in computational fluid dynamics(CFD)simulation is time-consuming for different lining structures,and usually takes around a week per case using the traditional direct modeling method.A parametric modeling tool has been developed to quickly generate various converter structures with quality structured grids within seconds,based on Python and OpenFOAM software.CFD simulations were established and validated using hydraulic modeling to investigate the flow dynamics and lining erosion characteristics in a 100 t top–bottom combined blowing converter under different H/D ratios and campaign stages(initial,middle,and late).The results show that the average molten bath velocity is positively correlated with bath depth.An increase in bath depth extends the path length for kinetic energy transfer of combined blowing gas streams.Excessively large bath depth or diameter will deteriorate the flow pattern and result into corresponding dead zones.Furnace wall and bottom erosion intensifies at higher H/D ratios but decreases in the late campaign stages.The H/D ratio of 1.67 is recommended in the initial design stage considering the flow characteristics.In the late campaign stage,increasing the bottom-blowing flow rate and carrying out furnace maintenance operations are recommended to maintain metallurgical efficiency and lining safety.展开更多
In the future power-electronics-dominated power systems,grid-forming(GFM)converters have been regarded as important devices to actively establish frequency and voltage,so as to provide essential grid support.However,d...In the future power-electronics-dominated power systems,grid-forming(GFM)converters have been regarded as important devices to actively establish frequency and voltage,so as to provide essential grid support.However,due to their voltage source behavior and emulated swing dynamics,GFM converters may encounter low-frequency oscillations(LFOs)when connected to strong grids,which belongs to the self-stability problem of GFM converters.Moreover,GFM converters will also interact with grid-following(GFL)converters and thus impact the mid-frequency oscillations(MFOs)induced by phase-locked loops(PLLs).It has been preliminarily shown in the literature that GFM converters can help stabilize the PLL-induced MFOs,but currently,there is a lack of systematic design methods to coordinate the self-stability and stabilizing ability of GFM converters.This paper addresses this gap by revisiting the impedance model of a typical GFM converter and briefly analyze the oscillations caused by converters.Based on our analysis,we propose a frequency-partitioned synthesis design framework to enable dynamic virtual impedance(DVI)in GFM converters,aiming to enhance their self-stability and stabilizing ability simultaneously.Particularly,a self-stabilizing module is designed to ensure robust device-level damping,with control parameters auto-tuned using H∞methods.In parallel,a stabilizing module is introduced to stabilize GFL converters and enhance the system-level stability,which utilizes a perceive-and-optimize tuning strategy.Simulation results validate the effectiveness of the proposed synthesis DVI framework.展开更多
Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)...Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)control strategy based on a power outer loop and voltage-current inner loops,aiming to enhance the stability and current-limiting capability of GFM converters during grid fault conditions.During voltage sags,the GFM converter’s voltage source behavior is maintained by dynamically adjusting the reactive power reference to provide voltage support,thereby effectively suppressing the steady-state component of the fault current.To address the active power imbalance induced by voltage sags,a dynamic active power reference correction method based on apparent power is designed to mitigate power angle oscillations and limit transient current.Moreover,an adaptive virtual impedance loop is implemented to enhance dynamic transient current-limiting performance during the fault initiation phase.This approach improves the responsiveness of the inner loop and ensures safe system operation under various fault severities.Under asymmetric fault conditions,a negative-sequence reactive current compensation strategy is incorporated to further suppress negative-sequence voltage and improve voltage symmetry.The proposed control scheme enables coordinated operation of multiple control objectives,including voltage support,current suppression,and power angle stability,across different fault scenarios.Finally,MATLAB/Simulink simulation results validate the effectiveness of the proposed strategy,showcasing its superior performance in current limiting and power angle stability,thereby significantly enhancing the system’s fault ride-through capability.展开更多
The transient synchronization stability of grid-forming converters(GFMCs)is significantly challenged under grid voltage sags.Continuous efforts have been devoted to analyzing the GFMC transient stability,with limited ...The transient synchronization stability of grid-forming converters(GFMCs)is significantly challenged under grid voltage sags.Continuous efforts have been devoted to analyzing the GFMC transient stability,with limited attention paid to the impacts of control loop dynamics.However,the complex control dynamics,especially the interactions between the active/reactive power control loops and the current saturation process(CSP),are crucial for accurately describing the transient behavior and evaluating the stability.Thus,in this study,a new large-signal GFMC model is established,considering the reactive power control(RPC)with different kinds of controllers and the CSP simultaneously.It is revealed that GFMC does not switch to the current-limited mode immediately,and the dynamics of RPC further affect the transient behavior before the current limiting significantly.Hence,the complex control dynamics can alter the mode switching point of current saturation,thereby increasing the risk of loss of synchronization(LOS).Based on the above findings,comprehensive comparisons of typical RPC controllers are presented to facilitate practical engineering applications.A unified stability enhancement method is proposed for solving the problem of LOS.Finally,experiments validate the correctness of the analysis and the effectiveness of the proposed control strategy.展开更多
In order to solve the problems of slow dynamic response and difficult multi-source coordination of solar electric vehicle charging stations under intermittent renewable energy,this paper proposes a hardware-algorithm ...In order to solve the problems of slow dynamic response and difficult multi-source coordination of solar electric vehicle charging stations under intermittent renewable energy,this paper proposes a hardware-algorithm co-design framework:the T-type three-level bidirectional converter(100 kHz switching frequency)based on silicon carbide(SiC)MOSFET is deeply integrated with fuzzy model predictive control(Fuzzy-MPC).At the hardware level,the switching trajectory and resonance suppression circuit(attenuation resonance peak 18 dB)are optimized,and the total loss is reduced by 23%compared with the traditional silicon-based IGBT.At the algorithm level,the adaptive parameter update mechanism and multi-objective rolling optimization are adopted,and the 5 ms level dynamic power allocation is realized by relying on edge computing.Experiments on 800 V DC microgrid(including 600 kW photovoltaic and 150 A·h energy storage)built based on MATLAB/Simulink hardware-in-the-loop(HIL)platform show that the system shortens the battery charging time from 42 to 28 min(the charging speed is increased by 33%).Through the 78%valley power utilization rate,the power purchase cost of high-priced power grids was significantly reduced,and the levelized electricity price decreased by 10.3%;Under the irradiation fluctuation,the renewable energy consumption rate increases by 10.1%,and the DC bus voltage fluctuation is stable within±10 V when the load step is±30%.The co-design provides an economically feasible and dynamically robust solution for the efficient integration of PV-ESG-EV in the smart grid.展开更多
A multi-phase stacked interleaved buck converter(SIBC)is suitable for large-power water electrolysis applications due to its merits of high current output capability and zero output current ripple.However,the auxiliar...A multi-phase stacked interleaved buck converter(SIBC)is suitable for large-power water electrolysis applications due to its merits of high current output capability and zero output current ripple.However,the auxiliary converter used to compensate for the current ripple still has to withstand high voltage stress.This paper proposes a new multi-phase SIBC applied in the multicarrier energy system integrating electricity,heat,and hydrogen.A resistor-capacitor voltage divider is used to provide the input voltage of the auxiliary converter and as a heater for the thermal loads.Thus,the voltage stress of the auxiliary converter can be reduced at a low cost,and the size of the filter inductor can be reduced.With accurate voltage and current analysis and appropriate parameter design,the voltage stresses of both the switches and capacitors in the auxiliary converter can be further limited within an expected range.The experimental results verify the correctness of the topology,modulation,analysis,and design methods.A comparison with the conventional method is made in terms of cost,volume,and efficiency to show the advantages of the proposed method.展开更多
As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the...As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the fault current elimination for MM-DC/DC remains a research gap,which limits the wide application of the MVDC system.To fulfil this research gap,the contribution of this paper is revealing the fault current characteristics of MM-DC/DC based on half-bridge and full-bridge submodules(HBSM and FBSM)and proposing a novel MM-DC/DC based on hybrid HBSM and thyristor-diode module(TDM).By integrating TDM in the upper bridge arm of one phase and the down bridge arm of the other phase in MM-DC/DC,the MM-DC/DC achieves self-elimination of fault currents.The basic concept is using the energy at the healthy side to modulate a reverse voltage source(RVS)at the faulty side of MM-DC/DC,forcing fault current through TDM pass across zero.TDM can extinguish the resulting fault current.The parameter design and control strategy of the novel MM-DC/DC are discussed.Simulation is carried out for verification,and the results show that fault current can be eliminated within several milliseconds without causing excessive operating losses and costs.展开更多
To address the issue of abnormal energy consumption fluctuations in the converter steelmaking process,an integrated diagnostic method combining the gray wolf optimization(GWO)algorithm,support vector machine(SVM),and ...To address the issue of abnormal energy consumption fluctuations in the converter steelmaking process,an integrated diagnostic method combining the gray wolf optimization(GWO)algorithm,support vector machine(SVM),and K-means clustering was proposed.Eight input parameters—derived from molten iron conditions and external factors—were selected as feature variables.A GWO-SVM model was developed to accurately predict the energy consumption of individual heats.Based on the prediction results,the mean absolute percentage error and maximum relative error of the test set were employed as criteria to identify heats with abnormal energy usage.For these heats,the K-means clustering algorithm was used to determine benchmark values of influencing factors from similar steel grades,enabling root-cause diagnosis of excessive energy consumption.The proposed method was applied to real production data from a converter in a steel plant.The analysis reveals that heat sample No.44 exhibits abnormal energy consumption,due to gas recovery being 1430.28 kg of standard coal below the benchmark level.A secondary contributing factor is a steam recovery shortfall of 237.99 kg of standard coal.This integrated approach offers a scientifically grounded tool for energy management in converter operations and provides valuable guidance for optimizing process parameters and enhancing energy efficiency.展开更多
Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial loss...Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial losses due to operational downtime but also to serious risks to human safety.The capacitors forming the output filter,typically aluminumelectrolytic capacitors(AECs),are among the most critical and susceptible components in power converters.The electrolyte in AECs often evaporates over time,causing the internal resistance to rise and the capacitance to drop,ultimately leading to component failure.Detecting this fault requires measuring the current in the capacitor,rendering the method invasive and frequently impractical due to spatial constraints or operational limitations imposed by the integration of a current sensor in the capacitor branch.This article proposes the implementation of an online noninvasive fault diagnosis technique for estimating the Equivalent Series Resistance(ESR)and Capacitance(C)values of the capacitor,employing a combination of signal processing techniques(SPT)and machine learning(ML)algorithms.This solution relies solely on the converter’s input and output signals,therefore making it a non-invasive approach.The ML algorithm used was linear regression,applied to 27 attributes,21 of which were generated through feature engineering to enhance the model’s performance.The proposed solution demonstrates an R^(2) score greater than 0.99 in the estimation of both ESR and C.展开更多
Dear Editor,This letter investigates the grid-forming control for power converters.Recently,grid-forming control based on matching of synchronous machines was suggested by using continuous measurements.In the present ...Dear Editor,This letter investigates the grid-forming control for power converters.Recently,grid-forming control based on matching of synchronous machines was suggested by using continuous measurements.In the present letter,we suggest a digital implementation using artificial delays where the controller employs the discrete-time measurements only.展开更多
In this paper,a stand-alone photovoltaic(PV)system based on a Double Ended Forward Converter(DEFC)is presented.The proposed converter is specified for 48 V,100Wapplications as most of the equipment used in telecommuni...In this paper,a stand-alone photovoltaic(PV)system based on a Double Ended Forward Converter(DEFC)is presented.The proposed converter is specified for 48 V,100Wapplications as most of the equipment used in telecommunication and aircraft fall in this range.The literature has limited potential application of DEFCin PV systems.The research work deals with an in-depth study of DEFCand proposes an improvedDEFCfor PV applications with battery backup.Besides,a bi-directional dc-dc converter for the battery is integrated to track theMaximumPower Point(MPP)of the PV generator.The converter is examined under variable irradiance and load conditions,and the analytical analysis of boundary conditions are implemented.The converter’s architecture also ensures built-in I-V curve tracing for the identification of MPP of PV generator.It offers low voltage stresses across switches and avoids sinking power supply and core resetting circuits.The topology’s behavior is analyzed based onMPP achievement and maintaining output under different conditions of battery backup availability,environmental,and load conditions.The PV system architecture is designed and analyzed theoretically and verified with simulations on the PSIM software.展开更多
The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system sta...The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.展开更多
The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.Howev...The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.However,most scholars currently focus on modifying methods to enhance model accuracy,while overlooking the extent to which input parameters influence accuracy.To address this issue,in this study,a prediction model for the endpoint carbon content in the converter was developed using factor analysis(FA)and support vector machine(SVM)optimized by improved particle swarm optimization(IPSO).Analysis of the factors influencing the endpoint carbon content during the converter smelting process led to the identification of 21 input parameters.Subsequently,FA was used to reduce the dimensionality of the data and applied to the prediction model.The results demonstrate that the performance of the FA-IPSO-SVM model surpasses several existing methods,such as twin support vector regression and support vector machine.The model achieves hit rates of 89.59%,96.21%,and 98.74%within error ranges of±0.01%,±0.015%,and±0.02%,respectively.Finally,based on the prediction results obtained by sequentially removing input parameters,the parameters were classified into high influence(5%-7%),medium influence(2%-5%),and low influence(0-2%)categories according to their varying degrees of impact on prediction accuracy.This classi-fication provides a reference for selecting input parameters in future prediction models for endpoint carbon content.展开更多
The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can ...The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can lead to significant issues.This paper reviews the development of high-power,reliable charging solutions by examining the converter topologies used in rectifiers and converters that transfer electricity from the grid to EV batteries.It covers technical details,ongoing developments,and challenges related to these topologies and control strategies.The integration of rapid charging stations has introduced various Power Quality(PQ)issues,such as voltage fluctuations,harmonic distortion,and supra-harmonics,which are discussed in detail.The paper also highlights the benefits of controlled EV charging and discharging,including voltage and frequency regulation,reactive power compensation,and improved power quality.Efficient energy management and control strategies are crucial for optimizing EV battery charging within microgrids to meet increasing demand.Charging stations must adhere to specific converter topologies,control strategies,and industry standards to function correctly.The paper explores microgrid architectures and control strategies that integrate EVs,energy storage units(ESUs),and Renewable Energy Sources(RES)to enhance performance at charging points.It emphasizes the importance of various RES-connected architectures and the latest power converter topologies.Additionally,the paper provides a comparative analysis of microgrid-based charging station architectures,focusing on energy management,control strategies,and charging converter controls.The goal is to offer insights into future research directions in EV charging systems,including architectural considerations,control factors,and their respective advantages and disadvantages.展开更多
This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and stru...This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.展开更多
With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist i...With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist in the field testing methodologies for wave energy converters(WECs).In this paper,a numerical wave field of the Dawanshan Island Sea Area in Zhuhai City is constructed based on the MIKE21 SW wave model and by using an NCEP wind field driving model.In conjunction with the IEC-62600-100 standard,by taking site testing of the“Wanshan”wave energy converter on which a sea trial has been conducted in Dawanshan Island of Zhuhai city as an example,research on-site testing method for a wave energy converter has been carried out.The wave measurement position for the“Wanshan”converter was determined by combining statistically analyzed field data with a validated numerical wave model.By comparing a valid wave height at the position where a wave rider is located with a valid wave height at the position where the“Wanshan”wave energy converter is situated,the correlation coefficient between simulation and observed data reached 0.90,with a root-mean-square error of 0.19.The representativeness of wave measurement data during site testing is verified and can be used as a basis for calculating the input energy of the“Wanshan”wave energy converter.展开更多
In this paper, we proposed an output voltage stabilization of a DC-DC Zeta converter using hybrid control. We modeled the Zeta converter under continuous conduction mode operation. We derived a switching control law t...In this paper, we proposed an output voltage stabilization of a DC-DC Zeta converter using hybrid control. We modeled the Zeta converter under continuous conduction mode operation. We derived a switching control law that brings the output voltage to the desired level. Due to infinite switching occurring at the desired level, we enhanced the switching control law by allowing a sizeable output voltage ripple. We derived mathematical models that allow one to choose the desired switching frequency. In practice, the existence of the non-ideal properties of the Zeta converter results in steady-state output voltage error. By analyzing the power loss in the zeta converter, we proposed an improved switching control law that eliminates the steady-state output voltage error. The effectiveness of the proposed method is illustrated with simulation results.展开更多
Bilinear structures are common in boost converters,and despite presenting interesting complexity,there are controls that have found general solutions under certain restrictions.Among these,the passive controls contain...Bilinear structures are common in boost converters,and despite presenting interesting complexity,there are controls that have found general solutions under certain restrictions.Among these,the passive controls containing the error dynamics of boost converters for a certain output structure are notable.While passive controls based on passivity demonstrate adequate performance,this work proposes a perturbation control based on the antisymmetric structure of boost converters to achieve better performance in terms of convergence speed and mean square error.Additionally,the perturbation control requires less error information for constructing the control signal,because it does not need information from all states or the entire passive output.Besides,the perturbation control uses the passivity of boost converters to ensure its stability.And finally,the perturbation control is compared with passive controls in a boost converter.展开更多
This paper presents an advanced control strategy for DC-DC buck converters utilizing Non-Minimal State Space (NMSS) representation combined with Proportional-Integral-Plus (PIP) control, optimized through Linear Quadr...This paper presents an advanced control strategy for DC-DC buck converters utilizing Non-Minimal State Space (NMSS) representation combined with Proportional-Integral-Plus (PIP) control, optimized through Linear Quadratic Regulator (LQR) design. The proposed approach leverages NMSS to eliminate the need for state observers, enhancing robustness against model mismatch and improving overall system performance. The PIP controller extends traditional PI control by incorporating additional dynamic feedback. Experimental results demonstrate that the NMSS-PIP-LQR controlled buck converter achieves excellent dynamic performance. The design procedure is fully documented, and microcontroller implementation issues are discussed.展开更多
文摘To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power increases current stress of devices and decreases efficiency,especially under light load conditions.Several modulation methods have been proposed to overcome the problem.They can reduce or eliminate either input or output side circulating power.In contrast,S-PWM not only eliminates both sides circulating power and reduces current stress,but also achieves zero-current-switching(ZCS)turn-on for all switches and ZCS turn-off for most across the full power range.No auxiliary or snubber circuits are increased.In addition,the control can be simplified so the transmitted power is related to only one variable.The S-PWM has four cases under different gain and power conditions.The detailed operation principle and modes of DAB under S-PWM are analyzed in the paper.In addition,four modulations in literature are discussed,and corresponding comparative analyses with S-PWM are given.Finally,a laboratory prototype is built to verify advantages and effectiveness of the proposed modulation.
基金fundings of National Natural Science Foundation of China(No.52374322)Baowu Group are highly appreciated.
文摘In the converter steelmaking process,the flow dynamics is closely related to the refractory lining structure of the bath,such as hearth height-to-diameter(H/D)ratio and lining erosion at different campaign stages.The step of pre-processing in computational fluid dynamics(CFD)simulation is time-consuming for different lining structures,and usually takes around a week per case using the traditional direct modeling method.A parametric modeling tool has been developed to quickly generate various converter structures with quality structured grids within seconds,based on Python and OpenFOAM software.CFD simulations were established and validated using hydraulic modeling to investigate the flow dynamics and lining erosion characteristics in a 100 t top–bottom combined blowing converter under different H/D ratios and campaign stages(initial,middle,and late).The results show that the average molten bath velocity is positively correlated with bath depth.An increase in bath depth extends the path length for kinetic energy transfer of combined blowing gas streams.Excessively large bath depth or diameter will deteriorate the flow pattern and result into corresponding dead zones.Furnace wall and bottom erosion intensifies at higher H/D ratios but decreases in the late campaign stages.The H/D ratio of 1.67 is recommended in the initial design stage considering the flow characteristics.In the late campaign stage,increasing the bottom-blowing flow rate and carrying out furnace maintenance operations are recommended to maintain metallurgical efficiency and lining safety.
基金supported by National Natural Science Foundation of China(U24B6008,U22B6008)State Grid Zhejiang Electric Power Co.,Ltd.Science,and Technology Project(B311DS240015).
文摘In the future power-electronics-dominated power systems,grid-forming(GFM)converters have been regarded as important devices to actively establish frequency and voltage,so as to provide essential grid support.However,due to their voltage source behavior and emulated swing dynamics,GFM converters may encounter low-frequency oscillations(LFOs)when connected to strong grids,which belongs to the self-stability problem of GFM converters.Moreover,GFM converters will also interact with grid-following(GFL)converters and thus impact the mid-frequency oscillations(MFOs)induced by phase-locked loops(PLLs).It has been preliminarily shown in the literature that GFM converters can help stabilize the PLL-induced MFOs,but currently,there is a lack of systematic design methods to coordinate the self-stability and stabilizing ability of GFM converters.This paper addresses this gap by revisiting the impedance model of a typical GFM converter and briefly analyze the oscillations caused by converters.Based on our analysis,we propose a frequency-partitioned synthesis design framework to enable dynamic virtual impedance(DVI)in GFM converters,aiming to enhance their self-stability and stabilizing ability simultaneously.Particularly,a self-stabilizing module is designed to ensure robust device-level damping,with control parameters auto-tuned using H∞methods.In parallel,a stabilizing module is introduced to stabilize GFL converters and enhance the system-level stability,which utilizes a perceive-and-optimize tuning strategy.Simulation results validate the effectiveness of the proposed synthesis DVI framework.
文摘Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)control strategy based on a power outer loop and voltage-current inner loops,aiming to enhance the stability and current-limiting capability of GFM converters during grid fault conditions.During voltage sags,the GFM converter’s voltage source behavior is maintained by dynamically adjusting the reactive power reference to provide voltage support,thereby effectively suppressing the steady-state component of the fault current.To address the active power imbalance induced by voltage sags,a dynamic active power reference correction method based on apparent power is designed to mitigate power angle oscillations and limit transient current.Moreover,an adaptive virtual impedance loop is implemented to enhance dynamic transient current-limiting performance during the fault initiation phase.This approach improves the responsiveness of the inner loop and ensures safe system operation under various fault severities.Under asymmetric fault conditions,a negative-sequence reactive current compensation strategy is incorporated to further suppress negative-sequence voltage and improve voltage symmetry.The proposed control scheme enables coordinated operation of multiple control objectives,including voltage support,current suppression,and power angle stability,across different fault scenarios.Finally,MATLAB/Simulink simulation results validate the effectiveness of the proposed strategy,showcasing its superior performance in current limiting and power angle stability,thereby significantly enhancing the system’s fault ride-through capability.
基金supported by the National Natural Science Foundation of China under Grant 52277184 and Grant 52277183.
文摘The transient synchronization stability of grid-forming converters(GFMCs)is significantly challenged under grid voltage sags.Continuous efforts have been devoted to analyzing the GFMC transient stability,with limited attention paid to the impacts of control loop dynamics.However,the complex control dynamics,especially the interactions between the active/reactive power control loops and the current saturation process(CSP),are crucial for accurately describing the transient behavior and evaluating the stability.Thus,in this study,a new large-signal GFMC model is established,considering the reactive power control(RPC)with different kinds of controllers and the CSP simultaneously.It is revealed that GFMC does not switch to the current-limited mode immediately,and the dynamics of RPC further affect the transient behavior before the current limiting significantly.Hence,the complex control dynamics can alter the mode switching point of current saturation,thereby increasing the risk of loss of synchronization(LOS).Based on the above findings,comprehensive comparisons of typical RPC controllers are presented to facilitate practical engineering applications.A unified stability enhancement method is proposed for solving the problem of LOS.Finally,experiments validate the correctness of the analysis and the effectiveness of the proposed control strategy.
基金Jiangsu Provincial College Student Innovation and Entrepreneurship Program(Grant No.SJCX25_2184)—“Multi-energy Complementary Optimization and Vehicle-Storage Bidirectional Interaction Technology Driven by Novel 5E Framework”(Principal Investigator:Yuan-Yuan ShiFunding Agency:Jiangsu Provincial Education Department)+3 种基金Huaian Natural Science Research Project(Grant No.HAB2024046)—“Optimal Control of Flexible Cold-Heat-Power Integrated System with Source-Grid-Load-Storage Coordination”(Principal Investigator:Jie JiFunding Agency:Huaian Science and Technology Bureau)Huaiyin Institute of TechnologyUniversity-funded Project(GrantNo.HGYK202511)—“Data-driven CooperativeOptimization Dispatch for Source-Grid-Load Systems”(Principal Investigator:Chu-Tong ZhangFunding Agency:Huaiyin Institute of Technology).
文摘In order to solve the problems of slow dynamic response and difficult multi-source coordination of solar electric vehicle charging stations under intermittent renewable energy,this paper proposes a hardware-algorithm co-design framework:the T-type three-level bidirectional converter(100 kHz switching frequency)based on silicon carbide(SiC)MOSFET is deeply integrated with fuzzy model predictive control(Fuzzy-MPC).At the hardware level,the switching trajectory and resonance suppression circuit(attenuation resonance peak 18 dB)are optimized,and the total loss is reduced by 23%compared with the traditional silicon-based IGBT.At the algorithm level,the adaptive parameter update mechanism and multi-objective rolling optimization are adopted,and the 5 ms level dynamic power allocation is realized by relying on edge computing.Experiments on 800 V DC microgrid(including 600 kW photovoltaic and 150 A·h energy storage)built based on MATLAB/Simulink hardware-in-the-loop(HIL)platform show that the system shortens the battery charging time from 42 to 28 min(the charging speed is increased by 33%).Through the 78%valley power utilization rate,the power purchase cost of high-priced power grids was significantly reduced,and the levelized electricity price decreased by 10.3%;Under the irradiation fluctuation,the renewable energy consumption rate increases by 10.1%,and the DC bus voltage fluctuation is stable within±10 V when the load step is±30%.The co-design provides an economically feasible and dynamically robust solution for the efficient integration of PV-ESG-EV in the smart grid.
基金supported in part by the National Natural Science Foundation of China(52077190)Cultivation Project for Basic Research and Innovation of Yanshan University(2021LGQN007)Science and Technology Project of Hebei Education Department(QN2024202).
文摘A multi-phase stacked interleaved buck converter(SIBC)is suitable for large-power water electrolysis applications due to its merits of high current output capability and zero output current ripple.However,the auxiliary converter used to compensate for the current ripple still has to withstand high voltage stress.This paper proposes a new multi-phase SIBC applied in the multicarrier energy system integrating electricity,heat,and hydrogen.A resistor-capacitor voltage divider is used to provide the input voltage of the auxiliary converter and as a heater for the thermal loads.Thus,the voltage stress of the auxiliary converter can be reduced at a low cost,and the size of the filter inductor can be reduced.With accurate voltage and current analysis and appropriate parameter design,the voltage stresses of both the switches and capacitors in the auxiliary converter can be further limited within an expected range.The experimental results verify the correctness of the topology,modulation,analysis,and design methods.A comparison with the conventional method is made in terms of cost,volume,and efficiency to show the advantages of the proposed method.
基金supported by Science and Technology Project of SGCC(5108-202218280A-2-370-XG).
文摘As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the fault current elimination for MM-DC/DC remains a research gap,which limits the wide application of the MVDC system.To fulfil this research gap,the contribution of this paper is revealing the fault current characteristics of MM-DC/DC based on half-bridge and full-bridge submodules(HBSM and FBSM)and proposing a novel MM-DC/DC based on hybrid HBSM and thyristor-diode module(TDM).By integrating TDM in the upper bridge arm of one phase and the down bridge arm of the other phase in MM-DC/DC,the MM-DC/DC achieves self-elimination of fault currents.The basic concept is using the energy at the healthy side to modulate a reverse voltage source(RVS)at the faulty side of MM-DC/DC,forcing fault current through TDM pass across zero.TDM can extinguish the resulting fault current.The parameter design and control strategy of the novel MM-DC/DC are discussed.Simulation is carried out for verification,and the results show that fault current can be eliminated within several milliseconds without causing excessive operating losses and costs.
基金support from the National Key R&D Program of China(Grant No.2020YFB1711100).
文摘To address the issue of abnormal energy consumption fluctuations in the converter steelmaking process,an integrated diagnostic method combining the gray wolf optimization(GWO)algorithm,support vector machine(SVM),and K-means clustering was proposed.Eight input parameters—derived from molten iron conditions and external factors—were selected as feature variables.A GWO-SVM model was developed to accurately predict the energy consumption of individual heats.Based on the prediction results,the mean absolute percentage error and maximum relative error of the test set were employed as criteria to identify heats with abnormal energy usage.For these heats,the K-means clustering algorithm was used to determine benchmark values of influencing factors from similar steel grades,enabling root-cause diagnosis of excessive energy consumption.The proposed method was applied to real production data from a converter in a steel plant.The analysis reveals that heat sample No.44 exhibits abnormal energy consumption,due to gas recovery being 1430.28 kg of standard coal below the benchmark level.A secondary contributing factor is a steam recovery shortfall of 237.99 kg of standard coal.This integrated approach offers a scientifically grounded tool for energy management in converter operations and provides valuable guidance for optimizing process parameters and enhancing energy efficiency.
文摘Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial losses due to operational downtime but also to serious risks to human safety.The capacitors forming the output filter,typically aluminumelectrolytic capacitors(AECs),are among the most critical and susceptible components in power converters.The electrolyte in AECs often evaporates over time,causing the internal resistance to rise and the capacitance to drop,ultimately leading to component failure.Detecting this fault requires measuring the current in the capacitor,rendering the method invasive and frequently impractical due to spatial constraints or operational limitations imposed by the integration of a current sensor in the capacitor branch.This article proposes the implementation of an online noninvasive fault diagnosis technique for estimating the Equivalent Series Resistance(ESR)and Capacitance(C)values of the capacitor,employing a combination of signal processing techniques(SPT)and machine learning(ML)algorithms.This solution relies solely on the converter’s input and output signals,therefore making it a non-invasive approach.The ML algorithm used was linear regression,applied to 27 attributes,21 of which were generated through feature engineering to enhance the model’s performance.The proposed solution demonstrates an R^(2) score greater than 0.99 in the estimation of both ESR and C.
基金supported by the National Natural Science Foundation of China(62403296,62303292,62173218).
文摘Dear Editor,This letter investigates the grid-forming control for power converters.Recently,grid-forming control based on matching of synchronous machines was suggested by using continuous measurements.In the present letter,we suggest a digital implementation using artificial delays where the controller employs the discrete-time measurements only.
文摘In this paper,a stand-alone photovoltaic(PV)system based on a Double Ended Forward Converter(DEFC)is presented.The proposed converter is specified for 48 V,100Wapplications as most of the equipment used in telecommunication and aircraft fall in this range.The literature has limited potential application of DEFCin PV systems.The research work deals with an in-depth study of DEFCand proposes an improvedDEFCfor PV applications with battery backup.Besides,a bi-directional dc-dc converter for the battery is integrated to track theMaximumPower Point(MPP)of the PV generator.The converter is examined under variable irradiance and load conditions,and the analytical analysis of boundary conditions are implemented.The converter’s architecture also ensures built-in I-V curve tracing for the identification of MPP of PV generator.It offers low voltage stresses across switches and avoids sinking power supply and core resetting circuits.The topology’s behavior is analyzed based onMPP achievement and maintaining output under different conditions of battery backup availability,environmental,and load conditions.The PV system architecture is designed and analyzed theoretically and verified with simulations on the PSIM software.
文摘The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.
基金financially supported by the National Natural Science Foundation of China(No.52174297).
文摘The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.However,most scholars currently focus on modifying methods to enhance model accuracy,while overlooking the extent to which input parameters influence accuracy.To address this issue,in this study,a prediction model for the endpoint carbon content in the converter was developed using factor analysis(FA)and support vector machine(SVM)optimized by improved particle swarm optimization(IPSO).Analysis of the factors influencing the endpoint carbon content during the converter smelting process led to the identification of 21 input parameters.Subsequently,FA was used to reduce the dimensionality of the data and applied to the prediction model.The results demonstrate that the performance of the FA-IPSO-SVM model surpasses several existing methods,such as twin support vector regression and support vector machine.The model achieves hit rates of 89.59%,96.21%,and 98.74%within error ranges of±0.01%,±0.015%,and±0.02%,respectively.Finally,based on the prediction results obtained by sequentially removing input parameters,the parameters were classified into high influence(5%-7%),medium influence(2%-5%),and low influence(0-2%)categories according to their varying degrees of impact on prediction accuracy.This classi-fication provides a reference for selecting input parameters in future prediction models for endpoint carbon content.
文摘The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can lead to significant issues.This paper reviews the development of high-power,reliable charging solutions by examining the converter topologies used in rectifiers and converters that transfer electricity from the grid to EV batteries.It covers technical details,ongoing developments,and challenges related to these topologies and control strategies.The integration of rapid charging stations has introduced various Power Quality(PQ)issues,such as voltage fluctuations,harmonic distortion,and supra-harmonics,which are discussed in detail.The paper also highlights the benefits of controlled EV charging and discharging,including voltage and frequency regulation,reactive power compensation,and improved power quality.Efficient energy management and control strategies are crucial for optimizing EV battery charging within microgrids to meet increasing demand.Charging stations must adhere to specific converter topologies,control strategies,and industry standards to function correctly.The paper explores microgrid architectures and control strategies that integrate EVs,energy storage units(ESUs),and Renewable Energy Sources(RES)to enhance performance at charging points.It emphasizes the importance of various RES-connected architectures and the latest power converter topologies.Additionally,the paper provides a comparative analysis of microgrid-based charging station architectures,focusing on energy management,control strategies,and charging converter controls.The goal is to offer insights into future research directions in EV charging systems,including architectural considerations,control factors,and their respective advantages and disadvantages.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3003805)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2022356)Guangzhou Basic and Applied Basic Research Project(Grant No.2023A04J0955).
文摘This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.
基金supported by the“National Ocean Technology Center Innovation Fund”under Project No.N3220Z002,led by Ning Jia.The official website of the National Ocean Technology Center is accessible at:http://www.notcsoa.org.cn/.
文摘With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist in the field testing methodologies for wave energy converters(WECs).In this paper,a numerical wave field of the Dawanshan Island Sea Area in Zhuhai City is constructed based on the MIKE21 SW wave model and by using an NCEP wind field driving model.In conjunction with the IEC-62600-100 standard,by taking site testing of the“Wanshan”wave energy converter on which a sea trial has been conducted in Dawanshan Island of Zhuhai city as an example,research on-site testing method for a wave energy converter has been carried out.The wave measurement position for the“Wanshan”converter was determined by combining statistically analyzed field data with a validated numerical wave model.By comparing a valid wave height at the position where a wave rider is located with a valid wave height at the position where the“Wanshan”wave energy converter is situated,the correlation coefficient between simulation and observed data reached 0.90,with a root-mean-square error of 0.19.The representativeness of wave measurement data during site testing is verified and can be used as a basis for calculating the input energy of the“Wanshan”wave energy converter.
文摘In this paper, we proposed an output voltage stabilization of a DC-DC Zeta converter using hybrid control. We modeled the Zeta converter under continuous conduction mode operation. We derived a switching control law that brings the output voltage to the desired level. Due to infinite switching occurring at the desired level, we enhanced the switching control law by allowing a sizeable output voltage ripple. We derived mathematical models that allow one to choose the desired switching frequency. In practice, the existence of the non-ideal properties of the Zeta converter results in steady-state output voltage error. By analyzing the power loss in the zeta converter, we proposed an improved switching control law that eliminates the steady-state output voltage error. The effectiveness of the proposed method is illustrated with simulation results.
基金supported by the Secretaría de Investigación y Posgrado(SIP),and the Comisión de Operacióny Fomento de Actividades Académicas(COFAA),both from the Instituto Politécnico Nacional(IPN)by the Secretaría de Ciencia,Humanidades,Tecnologíae Innovación(SECIHTI),México.
文摘Bilinear structures are common in boost converters,and despite presenting interesting complexity,there are controls that have found general solutions under certain restrictions.Among these,the passive controls containing the error dynamics of boost converters for a certain output structure are notable.While passive controls based on passivity demonstrate adequate performance,this work proposes a perturbation control based on the antisymmetric structure of boost converters to achieve better performance in terms of convergence speed and mean square error.Additionally,the perturbation control requires less error information for constructing the control signal,because it does not need information from all states or the entire passive output.Besides,the perturbation control uses the passivity of boost converters to ensure its stability.And finally,the perturbation control is compared with passive controls in a boost converter.
文摘This paper presents an advanced control strategy for DC-DC buck converters utilizing Non-Minimal State Space (NMSS) representation combined with Proportional-Integral-Plus (PIP) control, optimized through Linear Quadratic Regulator (LQR) design. The proposed approach leverages NMSS to eliminate the need for state observers, enhancing robustness against model mismatch and improving overall system performance. The PIP controller extends traditional PI control by incorporating additional dynamic feedback. Experimental results demonstrate that the NMSS-PIP-LQR controlled buck converter achieves excellent dynamic performance. The design procedure is fully documented, and microcontroller implementation issues are discussed.
