With the growing integration of renewable energy sources(RESs)and smart interconnected devices,conventional distribution networks have turned to active distribution networks(ADNs)with complex system model and power fl...With the growing integration of renewable energy sources(RESs)and smart interconnected devices,conventional distribution networks have turned to active distribution networks(ADNs)with complex system model and power flow dynamics.The rapid fluctuation of RES power may easily result in frequent voltage violation issues.Taking the flexible RES reactive power as control variables,this paper proposes a two-layer control scheme with Koopman wide neural network(WNN)based model predictive control(MPC)method for optimal voltage regulation and network loss reduction.Based on Koopman operator theory,a data-driven WNN method is presented to fit a high-dimensional linear model of power flow.With the model,voltage and network loss sensitivities are computed analytically,and utilized for ADN partition and control model formulation.In the lower level,a dual-mode adaptive switching MPC strategy is put forward for optimal voltage control and network loss optimization in each individual partition to decide the RES reactive power.The upper level is to calculate the adjustment coefficients of the RES reactive power given in the low level by taking the coupling effects of different partitions into account,and then the final reactive power dispatches of RESs are obtained to realize optimal control of voltage and network loss.Simulation results on two ADNs demonstrate that the proposed strategy can reliably maintain the voltage at each node within the secure range,reduce network power losses,and enhance the overall system security and economic efficiency.展开更多
To address the issue of transient low-voltage instability in AC-DC hybrid power systems following large disturbances,conventional voltage assessment and control strategies typically adopt a sequential“assess-then-act...To address the issue of transient low-voltage instability in AC-DC hybrid power systems following large disturbances,conventional voltage assessment and control strategies typically adopt a sequential“assess-then-act”paradigm,which struggles to simultaneously meet the requirements for both high accuracy and rapid response.This paper proposes a transient voltage assessment and control method based on a hybrid neural network incorporated with an improved snow ablation optimization(ISAO)algorithm.The core innovation of the proposed method lies in constructing an intelligent“physics-informed and neural network-integrated”framework,which achieves the integration of stability assessment and control strategy generation.Firstly,to construct a highly correlated input set,response characteristics reflecting the system’s voltage stable/unstable states are screened.Simultaneously,the transient voltage severity index(TVSI)is introduced as a comprehensive metric to quantify the system’s post-disturbance transient voltage performance.Furthermore,the load bus voltage sensitivity index(LVSI)is defined as the ratio of the voltage change magnitude at a load node(or bus)to the change in the system-level TVSI,thereby pinpointing the response characteristics of critical load nodes.Secondly,both the transient voltage stability assessment result and its corresponding under-voltage load shedding(UVLS)control amount are jointly utilized as the outputs of the response-driven model.Subsequently,the snow ablation optimization(SAO)algorithm is enhanced using a good point set strategy and a Gaussian mutation strategy.This improved algorithm is then employed to optimize the key hyperparameters of the hybrid neural network.Finally,the superiority of the proposed method is validated on a modified CEPRI-36 system and an actual power grid case.Comparisons with various artificial intelligence methods demonstrate its significant advantages in model speed and accuracy.Additionally,when compared to traditional emergency control schemes and UVLS strategies,the proposed method exhibits exceptional rapidness and real-time capability in control decision-making.展开更多
Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transien...Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transient stability.This paper investigates a common countermeasure involving a PI-based DC voltage controller for GFM-PV systems,revealing that their small-signal stability is sensitive to parameter tuning.The study develops a generalized DC voltage-dominated 2nd-order GFM model and successfully conducts complex torque analysis,showing that this approach can be effectively extended to other dynamics governed by DC voltage-dominated GFM systems.Subsequently,the paper establishes a stability criterion for GFM-PV systems and proposes a parameter tuning method for DC voltage controllers that incorporates damping margin considerations.The performance of the tuned single-machine-infinite-bus GFM-PV system is validated on the RT-LAB real-time simulation platform under scenarios involving solar irradiance fluctuations and grid frequency disturbances.The proposed method proves effective in ensuring the stability of the GFM-PV system,with robust theoretical support.展开更多
When the converter bus voltage of a voltage source converter-based high voltage direct current(VSC-HVDC)system drops below a certain predetermined threshold,the system enters low-voltage ride-through(LVRT)mode to avoi...When the converter bus voltage of a voltage source converter-based high voltage direct current(VSC-HVDC)system drops below a certain predetermined threshold,the system enters low-voltage ride-through(LVRT)mode to avoid overcurrent and potential equipment failure,during which it operates as a controlled current source.The influence mechanism of LVRT control strategies on short-circuit current and overall system stability remains not yet fully and systematically investigated.First,this paper provides an overview of several LVRT strategies for VSC-HVDC systems and examines their effects on short-circuit current contribution.Next,it analyzes in detail the mechanisms through which active and reactive currents injected during LVRT impact system frequency stability,voltage stability,and synchronization stability.To address these interrelated issues,an optimized and comprehensive LVRT strategy incorporating short-circuit current constraints is proposed.The approach determines the active current ratio based on system frequency stability requirements and dynamically adjusts the active current recovery rate via phase control of the VSC-HVDC bus.The remaining capacity is allocated to reactive current support,thereby enhancing voltage and synchronization stability while maintaining sufficient short-circuit current margin and system frequency stability.Finally,simulations conducted on the PSS/E platform,using actual grid data from a selected cross-section system,validate convincingly the effectiveness of the proposed parameter optimization strategy for VSC-HVDC low-voltage ride-through.展开更多
The integration of a high proportion of renewable energy introduces significant challenges for the adaptability of traditional fault nature identification methods.To address these challenges,this paper presents a nove...The integration of a high proportion of renewable energy introduces significant challenges for the adaptability of traditional fault nature identification methods.To address these challenges,this paper presents a novel fault nature identification method for renewable energy grid-connected interconnection lines,leveraging wavelet packet decomposition and voltage waveform time-frequency morphology comparison algorithms.First,the paper investigates the harmonic injection mechanism during non-full-phase operation following fault isolation in photovoltaic renewable energy systems,and examines the voltage characteristics of faulted phases in renewable energy scenarios.The analysis reveals that substantial differences exist in both the time and frequency domains of phase voltages before and after the extinction of transient faults,whereas permanent faults do not exhibit such variations.Building on this observation,the paper proposes a voltage time-frequency feature extraction method based on wavelet packet decomposition,wherein low-frequency waveform components are selected to characterize fault features.Subsequently,a fault nature identification method is introduced,based on a voltage waveform time-frequency morphology comparison.By employing a windowing technique to quantify waveform differences before and after arc extinction,this method effectively distinguishes between permanent and transient faults and accurately determines the arc extinction time.Finally,a 220 kV renewable energy grid connection line model is developed using PSCAD for verification.The results demonstrate that the proposed method is highly adaptable across various fault locations,transition resistances,and renewable energy control strategies,and can reliably identify fault nature in renewable energy grid connection scenarios.展开更多
Accurate estimation of battery health status plays a crucial role in battery management systems.However,the lack of operational data still affects the accuracy of battery state of health(SOH)estimation.For this reason...Accurate estimation of battery health status plays a crucial role in battery management systems.However,the lack of operational data still affects the accuracy of battery state of health(SOH)estimation.For this reason,a SOH estimation method is proposed based on charging data reconstruction combined with image processing.The charging voltage data is used to train the least squares generative adversarial network(LSGAN),which is validated under different levels of missing data.From a visual perspective,the Gram angle field method is applied to convert one-dimensional time series data into image data.This method fully preserves the time series characteristics and nonlinear evolution patterns,which avoids the difficulties and limited expressive power associated with manual feature extraction.At the same time,the Swin Transformer model is introduced to extract global structures and local details from images,enabling better capture of sequence change trends.Combined with the long short-term memory network(LSTM),this enables accurate estimation of battery SOH.Two different types of batteries are used to validate the test.The experimental results show that the proposed method has good estimation accuracy under different training proportions.展开更多
Given the wide application of DC grids,the protection equipment of power grids must be improved during the fault period.This study proposes an integrated multiport flexible voltage clamp circuit breaker with a DC chop...Given the wide application of DC grids,the protection equipment of power grids must be improved during the fault period.This study proposes an integrated multiport flexible voltage clamp circuit breaker with a DC chopper acting on the receiving end converter to solve the DC short circuit fault and surplus power because of AC low-voltage fault;it has a modular design.As a DC circuit breaker,the device utilizes the voltage-clamping principle and thyristor semi-control to remove faults.As the fault current increases,the branch circuit outputs different voltage levels by selecting different gears,thereby controlling the voltage-clamping effect.This device can distinguish between different fault types to prevent secondary shocks in the system.As a DC chopper,the voltage at both ends of the energy dissipation resistor is varied by switching submodules,consuming surplus power to complete AC low-voltage faults and minimizing the impact of low-voltage faults on the system’s transmission capacity.Finally,the effectiveness and applicability of the equipment are verified using wind turbines connected to a flexible DC transmission three-terminal power grid model in PSCAD/EMTDC,and two fault simulation types are analyzed.A comparison of the electrical quantities(fault current,system voltage and branch voltage)of the proposed circuit breaker with other similar equipment shows that due to the efficiency of the proposed equipment,the peak fault current is reduced by at least 35.8%.The required voltage stress of key power electronic equipment is reduced by at least 71.5%.Therefore,the equipment ensures that the per-unit voltage of the DC system does not exceed 1.05 during AC fault crossing.展开更多
The implementation of multifunctional application scenarios for mobile terminal devices has increased the energy density requirements of batteries.Increasing the charging voltage can rapidly increase the specific capa...The implementation of multifunctional application scenarios for mobile terminal devices has increased the energy density requirements of batteries.Increasing the charging voltage can rapidly increase the specific capacity of layered transition metal oxides;however,it also exacerbates the release of lattice oxygen and the contraction of the unit cell.Ternary materials are designed in a secondary particle state to meet the requirements of power battery applications.Therefore,to create ternary materials that can operate under ultrahigh voltages,attention should be given to both surface modification and particle integrity maintenance.By utilizing elemental selenium(Se)with a low melting point,easy sublimation,and multiple variable valence states,deep grain boundary modification was implemented inside the particles.The performance of the cathode material was evaluated through pouch cells,and the improvement mechanism was explored through molecular dynamics simulation calculations.Under the protection of a three-dimensional Se-rich modified layer,LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)achieved stable operation at ultrahigh voltages(4.6 V vs.Li/Li^(+));a sacrificial protection mechanism based on the chronic decomposition of the Se-rich layer was proposed to explain the efficacy of Se modification in stabilizing ternary materials.This deep grain boundary modification based on elemental Se provides a new solution for the ultrahigh-voltage operation of transition metal oxides and provides a scientific basis and technical support for solving the interface contact problem of all-solid-state batteries.展开更多
Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such...Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such as low-voltage input photovoltaic power systems and electric vehicle systems.However,they usually require more high voltage rating switches and flying capacitors along with boosting capability.Furthermore,they suffer from high pulse currents at the switching transients.Aiming to solve these issues,this article proposes a new self-balancing three-phase five-level inverter based on the switched-capacitor(5L-SCTPNPC),which reduces the dc voltage requirement.The number of active switches is relatively smaller and seven active switches are required per phase.Especially,a soft-charging circuit for FC is designed to limit the impulse charging current.Compared to conventional multilevel inverters,the proposed five-level inverter reduces dc bus voltage by 50%.Significantly,the voltage stress of FC and the switches in parallel with FC are all reduced by 50%in comparison with some existing similar boosting five-level active-neutral-point-clamped(5L-BANPC)inverters.The operating principles,modulation strategy,and the design of the FC and charging inductor are provided in detailly.A comprehensive comparison study has been made to highlight the merits of the proposed inverter.Finally,the simulations and experiments validate the feasibility of the proposed topology.展开更多
With the prevalence of renewable distributed energy resources(DERs)such as photovoltaics(PVs),modern active distribution networks(ADNs)suffer from voltage deviation and power quality issues.However,traditional voltage...With the prevalence of renewable distributed energy resources(DERs)such as photovoltaics(PVs),modern active distribution networks(ADNs)suffer from voltage deviation and power quality issues.However,traditional voltage control methods often face a trade-off between efficiency and effectiveness,and rarely ensure robust voltage safety under typical state perturbations in practical distribution grids.In this paper,a robust model-free voltage regulation approach is proposed which simultaneously takes security and robustness into account.In this context,the voltage control problem is formulated as a constrained Markov decision process(CMDP).A safety-augmented multiagent deep deterministic policy gradient(MADDPG)algorithm is the trained to enable real-time collaborative optimization of ADNs,aiming to maintain nodal voltages within safe operational limits while minimizing total line losses.Moreover,a robust regulation loss is introduced to ensure reliable performance under various state perturbations in practical voltage controls.The proposed regulation algorithm effectively balance efficiency,safety,and robustness,and also demonstrates potential for generalizing these characteristics to other applications.Numerical studies vali-date the robustness of the proposed method under varying state perturbations on the IEEE test cases and the optimal integrated control performance when compared to other benchmarks.展开更多
The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the ...The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the DCV transient behavior of a PLL-based DFIG system under asymmetrical grid faults.First,by considering the coupling characteristics of positive and negative sequence(PNS)components,a nonlinear largesignal model of DCV is developed.Furthermore,the transient characteristics of DCV under varying parameters are analyzed using phase trajectory diagrams.In addition,the transient stability(TS)mechanism of DCV during asymmetrical faults is examined through an en-ergy function approach.The analysis indicates that the transient instability of DCV is primarily associated with the control characteristics of PNS PLLs,while the TS level of DCV is mainly determined by the power coordination control between the rotor side converter and grid side converter.Moreover,a coordinated control strategy is proposed to enhance the TS of DCV under asymmet-rical grid faults.Finally,both simulation and experimental results are presented to validate the theoretical analysis and the effectiveness of the proposed strategy.展开更多
During sending-end faults in the hybrid cascaded HVDC(HC-HVDC)system,the transient voltage drop characteristics under the interaction of the AC/DC hybrid system remain unclear,and the reactive power support provided b...During sending-end faults in the hybrid cascaded HVDC(HC-HVDC)system,the transient voltage drop characteristics under the interaction of the AC/DC hybrid system remain unclear,and the reactive power support provided by the HC-HVDC to the sending-end AC system requires further investigation.To address this problem,the reactive power interaction coupling mechanism between the sending-end AC system and the HC-HVDC is revealed,and the transient voltage mathematical model considering fault severity and duration is established.Under the dynamic change of the AC system voltage,the difference between the reactive power provided only by the reactive power compensation devices and by the combined modular multilevel converters(MMC)and reactive power compensation devices is analyzed.It is concluded that using MMC to provide a proportion of reactive power enhances the reactive power support to the AC system during faults.Then,the transient voltage model considering the reactive power support of MMC is established,and the critical reactive power consumption of line commutated converter(LCC)is quantified.It is concluded that the reactive power consumption of LCC exceeding its critical value deteriorates the transient voltage.A coordinated support strategy for the sending-end AC system based on reactive power support of MMC and reactive power regulation of LCC is proposed.It can effectively address the challenge of weakened reactive power support to the AC system due to voltage drop,thereby preventing the unbalanced reactive power from deteriorating the transient voltage,and realizing active support of the tran-sient voltage.Finally,a simulation model is established on the PSCAD/EMTDC platform,and the simulation results validate the effectiveness of the proposed strategy in supporting the transient voltage,under different fault types,durations,severities,and locations.展开更多
The susceptibility of ore particles to electrical breakdown plays a critical role for high voltage pulse(HVP)breakage,yet its quantitative characterization still lacks deep understanding.Two indicators,namely breakdow...The susceptibility of ore particles to electrical breakdown plays a critical role for high voltage pulse(HVP)breakage,yet its quantitative characterization still lacks deep understanding.Two indicators,namely breakdown delay time(T_(d))and breakdown strength(E_(b))were compared,based on analysis on the two breakdown modes namely wavefront mode and post-wave mode.It was found that T_(d) is more suitable to characterize the susceptibility of ore particles to electrical breakdown in HVP breakage than E_(b).A probabilistic model based on the Weibull distribution is developed to describe the relation of breakdown probability to T_(d).Regression analyses were conducted to investigate how operating parameters and particle properties influence Td and size reduction degree of ore particles in HVP breakage.The regressed models demonstrate potential capability to predict metallic minerals content and HVP breakage degree based on operating parameters and particle properties.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
In position-sensorless brushless direct current(DC)motors(BLDCMs)fed by a four-switch three-phase(FSTP)inverter,only two phases are fully controlled,while the remaining phase is tied to the midpoint of the split DC-li...In position-sensorless brushless direct current(DC)motors(BLDCMs)fed by a four-switch three-phase(FSTP)inverter,only two phases are fully controlled,while the remaining phase is tied to the midpoint of the split DC-link capacitors.The voltage pulses required by inductance-based initial position detection can cause unequal discharge of the series capacitors,shifting the neutral-point voltage away from half of DC-link voltage(U_(dc)/2).This neutral-point drift breaks the spatial symmetry of the inverter voltage vectors,so the 360°electrical period can no longer be evenly partitioned into six sectors during initial rotor position detection.To address this issue,this paper proposes a detection-pulse injection sequence that explicitly accounts for the asymmetric voltage vectors of the FSTP inverter.With the proposed sequence,the initial rotor position can be identified within a 30°electrical sector.The method requires no additional voltage or current sensors,and experimental results confirm its feasibility.展开更多
Severe injuries due to electricity are rare,but when they occur,they may cause life-threatening conditions.In order to define the severity of electrical injuries,the most widely used classification is voltage power.In...Severe injuries due to electricity are rare,but when they occur,they may cause life-threatening conditions.In order to define the severity of electrical injuries,the most widely used classification is voltage power.Injuries are mainly classified into two categories as low voltage electrical injuries(LVEI)(<1000 V)and high voltage electrical injuries(>1000 V).Fatal injuries have been reported mostly after high-voltage electric shock.Low-voltage electricity current rarely causes severe trauma and complications.展开更多
With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as...With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.展开更多
This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) unde...This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) under high linear energy transfer heavyion experimentation.The experimental findings demonstrate that applying a negative back-gate bias to NMOS and a positive back-gate bias to PMOS enhances the SEU resistance of SRAM.Specifically,as the back-gate bias for N-type transistors(V_(nsoi)) decreases from 0 to-10 V,the SEU cross section decreases by 93.23%,whereas an increase in the back-gate bias for P-type transistors (V_(psoi)) from 0 to 10 V correlates with an 83.7%reduction in SEU cross section.Furthermore,a significant increase in the SEU cross section was observed with increase in supply voltage,as evidenced by a 159%surge at V_(DD)=1.98 V compared with the nominal voltage of 1.8 V.To explore the physical mechanisms underlying these experimental data,we analyzed the dependence of the critical charge of the circuit and the collected charge on the bias voltage by simulating SEUs using technology computer-aided design.展开更多
Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage...Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage transformer errors, particularly minor variations in multi-channel setups, remains challenging. This paper proposes a method for online error tracking of multi-channel capacitive voltage transformers using a Co-Prediction Matrix. The approach leverages the strong correlation between in-phase channels, particularly the invariance of the signal proportions among them. By establishing a co-prediction matrix based on these proportional relationships, The influence of voltage changes on the primary measurements is mitigated. Analyzing the relationships between the co-prediction matrices over time allows for inferring true measurement errors. Experimental validation with real-world data confirms the effectiveness of the method, demonstrating its capability to continuously track capacitive voltage transformer measurement errors online with precision over extended durations.展开更多
基金supported by the Science and Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.(J2024162).
文摘With the growing integration of renewable energy sources(RESs)and smart interconnected devices,conventional distribution networks have turned to active distribution networks(ADNs)with complex system model and power flow dynamics.The rapid fluctuation of RES power may easily result in frequent voltage violation issues.Taking the flexible RES reactive power as control variables,this paper proposes a two-layer control scheme with Koopman wide neural network(WNN)based model predictive control(MPC)method for optimal voltage regulation and network loss reduction.Based on Koopman operator theory,a data-driven WNN method is presented to fit a high-dimensional linear model of power flow.With the model,voltage and network loss sensitivities are computed analytically,and utilized for ADN partition and control model formulation.In the lower level,a dual-mode adaptive switching MPC strategy is put forward for optimal voltage control and network loss optimization in each individual partition to decide the RES reactive power.The upper level is to calculate the adjustment coefficients of the RES reactive power given in the low level by taking the coupling effects of different partitions into account,and then the final reactive power dispatches of RESs are obtained to realize optimal control of voltage and network loss.Simulation results on two ADNs demonstrate that the proposed strategy can reliably maintain the voltage at each node within the secure range,reduce network power losses,and enhance the overall system security and economic efficiency.
基金supported by the State Grid Shanxi Electric Power Company science and technology project“Research on Key Technologies for Voltage Stability Analysis and Control of UHV Transmission Sending-End Grid with Large-Scale Integration of Wind-Solar-Storage Systems”(520530240026).
文摘To address the issue of transient low-voltage instability in AC-DC hybrid power systems following large disturbances,conventional voltage assessment and control strategies typically adopt a sequential“assess-then-act”paradigm,which struggles to simultaneously meet the requirements for both high accuracy and rapid response.This paper proposes a transient voltage assessment and control method based on a hybrid neural network incorporated with an improved snow ablation optimization(ISAO)algorithm.The core innovation of the proposed method lies in constructing an intelligent“physics-informed and neural network-integrated”framework,which achieves the integration of stability assessment and control strategy generation.Firstly,to construct a highly correlated input set,response characteristics reflecting the system’s voltage stable/unstable states are screened.Simultaneously,the transient voltage severity index(TVSI)is introduced as a comprehensive metric to quantify the system’s post-disturbance transient voltage performance.Furthermore,the load bus voltage sensitivity index(LVSI)is defined as the ratio of the voltage change magnitude at a load node(or bus)to the change in the system-level TVSI,thereby pinpointing the response characteristics of critical load nodes.Secondly,both the transient voltage stability assessment result and its corresponding under-voltage load shedding(UVLS)control amount are jointly utilized as the outputs of the response-driven model.Subsequently,the snow ablation optimization(SAO)algorithm is enhanced using a good point set strategy and a Gaussian mutation strategy.This improved algorithm is then employed to optimize the key hyperparameters of the hybrid neural network.Finally,the superiority of the proposed method is validated on a modified CEPRI-36 system and an actual power grid case.Comparisons with various artificial intelligence methods demonstrate its significant advantages in model speed and accuracy.Additionally,when compared to traditional emergency control schemes and UVLS strategies,the proposed method exhibits exceptional rapidness and real-time capability in control decision-making.
基金supported in part by Northeast Branch of State Grid Corporation of China(52992624000W).
文摘Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transient stability.This paper investigates a common countermeasure involving a PI-based DC voltage controller for GFM-PV systems,revealing that their small-signal stability is sensitive to parameter tuning.The study develops a generalized DC voltage-dominated 2nd-order GFM model and successfully conducts complex torque analysis,showing that this approach can be effectively extended to other dynamics governed by DC voltage-dominated GFM systems.Subsequently,the paper establishes a stability criterion for GFM-PV systems and proposes a parameter tuning method for DC voltage controllers that incorporates damping margin considerations.The performance of the tuned single-machine-infinite-bus GFM-PV system is validated on the RT-LAB real-time simulation platform under scenarios involving solar irradiance fluctuations and grid frequency disturbances.The proposed method proves effective in ensuring the stability of the GFM-PV system,with robust theoretical support.
基金funded by State Grid Corporation of China,grant number DQ30DK24001L。
文摘When the converter bus voltage of a voltage source converter-based high voltage direct current(VSC-HVDC)system drops below a certain predetermined threshold,the system enters low-voltage ride-through(LVRT)mode to avoid overcurrent and potential equipment failure,during which it operates as a controlled current source.The influence mechanism of LVRT control strategies on short-circuit current and overall system stability remains not yet fully and systematically investigated.First,this paper provides an overview of several LVRT strategies for VSC-HVDC systems and examines their effects on short-circuit current contribution.Next,it analyzes in detail the mechanisms through which active and reactive currents injected during LVRT impact system frequency stability,voltage stability,and synchronization stability.To address these interrelated issues,an optimized and comprehensive LVRT strategy incorporating short-circuit current constraints is proposed.The approach determines the active current ratio based on system frequency stability requirements and dynamically adjusts the active current recovery rate via phase control of the VSC-HVDC bus.The remaining capacity is allocated to reactive current support,thereby enhancing voltage and synchronization stability while maintaining sufficient short-circuit current margin and system frequency stability.Finally,simulations conducted on the PSS/E platform,using actual grid data from a selected cross-section system,validate convincingly the effectiveness of the proposed parameter optimization strategy for VSC-HVDC low-voltage ride-through.
基金supported by State Grid Sichuan Electric Power Company science and technology project“Research on Key Technologies for Reclosing of High-Ratio New Energy Grid Connection Lines.”(Program No:52199723002Q).
文摘The integration of a high proportion of renewable energy introduces significant challenges for the adaptability of traditional fault nature identification methods.To address these challenges,this paper presents a novel fault nature identification method for renewable energy grid-connected interconnection lines,leveraging wavelet packet decomposition and voltage waveform time-frequency morphology comparison algorithms.First,the paper investigates the harmonic injection mechanism during non-full-phase operation following fault isolation in photovoltaic renewable energy systems,and examines the voltage characteristics of faulted phases in renewable energy scenarios.The analysis reveals that substantial differences exist in both the time and frequency domains of phase voltages before and after the extinction of transient faults,whereas permanent faults do not exhibit such variations.Building on this observation,the paper proposes a voltage time-frequency feature extraction method based on wavelet packet decomposition,wherein low-frequency waveform components are selected to characterize fault features.Subsequently,a fault nature identification method is introduced,based on a voltage waveform time-frequency morphology comparison.By employing a windowing technique to quantify waveform differences before and after arc extinction,this method effectively distinguishes between permanent and transient faults and accurately determines the arc extinction time.Finally,a 220 kV renewable energy grid connection line model is developed using PSCAD for verification.The results demonstrate that the proposed method is highly adaptable across various fault locations,transition resistances,and renewable energy control strategies,and can reliably identify fault nature in renewable energy grid connection scenarios.
基金supported in part by the National Natural Science Foundation of China(under Grant 62473309,62203352)the Shaanxi Outstanding Youth Science Fund Project(under Grant 2024JC-JCQN-68)+1 种基金the Xi’an Science and Technology Plan Project(under Grant 24GXFW0050)the Xi’an Key Laboratory(under Grant 24ZDSY0015).
文摘Accurate estimation of battery health status plays a crucial role in battery management systems.However,the lack of operational data still affects the accuracy of battery state of health(SOH)estimation.For this reason,a SOH estimation method is proposed based on charging data reconstruction combined with image processing.The charging voltage data is used to train the least squares generative adversarial network(LSGAN),which is validated under different levels of missing data.From a visual perspective,the Gram angle field method is applied to convert one-dimensional time series data into image data.This method fully preserves the time series characteristics and nonlinear evolution patterns,which avoids the difficulties and limited expressive power associated with manual feature extraction.At the same time,the Swin Transformer model is introduced to extract global structures and local details from images,enabling better capture of sequence change trends.Combined with the long short-term memory network(LSTM),this enables accurate estimation of battery SOH.Two different types of batteries are used to validate the test.The experimental results show that the proposed method has good estimation accuracy under different training proportions.
基金supported by National Natural Science Foundation of China(U2066208).
文摘Given the wide application of DC grids,the protection equipment of power grids must be improved during the fault period.This study proposes an integrated multiport flexible voltage clamp circuit breaker with a DC chopper acting on the receiving end converter to solve the DC short circuit fault and surplus power because of AC low-voltage fault;it has a modular design.As a DC circuit breaker,the device utilizes the voltage-clamping principle and thyristor semi-control to remove faults.As the fault current increases,the branch circuit outputs different voltage levels by selecting different gears,thereby controlling the voltage-clamping effect.This device can distinguish between different fault types to prevent secondary shocks in the system.As a DC chopper,the voltage at both ends of the energy dissipation resistor is varied by switching submodules,consuming surplus power to complete AC low-voltage faults and minimizing the impact of low-voltage faults on the system’s transmission capacity.Finally,the effectiveness and applicability of the equipment are verified using wind turbines connected to a flexible DC transmission three-terminal power grid model in PSCAD/EMTDC,and two fault simulation types are analyzed.A comparison of the electrical quantities(fault current,system voltage and branch voltage)of the proposed circuit breaker with other similar equipment shows that due to the efficiency of the proposed equipment,the peak fault current is reduced by at least 35.8%.The required voltage stress of key power electronic equipment is reduced by at least 71.5%.Therefore,the equipment ensures that the per-unit voltage of the DC system does not exceed 1.05 during AC fault crossing.
基金supported by the National Natural Science Foundation of China (52302259)the China Postdoctoral Science Foundation (CPSF) under Grant Number 2023M741479+4 种基金the Postdoctoral Fellowship Program of CPSF under Grant Number GZB20240280the Jiangxi Provincial Natural Science Foundation (20224ACB218006)the financial support from High-level Talent Research Special Funds of Jiangxi University of Science and Technology (Grant No. 205200100670)the Jiangxi Provincial Key Laboratory of Power Energy Storage Batteries and Materials (2024SSY10011)the Major Scientific and Technological Research R&D Special Project of Jiangxi Province(20244AFI92002)
文摘The implementation of multifunctional application scenarios for mobile terminal devices has increased the energy density requirements of batteries.Increasing the charging voltage can rapidly increase the specific capacity of layered transition metal oxides;however,it also exacerbates the release of lattice oxygen and the contraction of the unit cell.Ternary materials are designed in a secondary particle state to meet the requirements of power battery applications.Therefore,to create ternary materials that can operate under ultrahigh voltages,attention should be given to both surface modification and particle integrity maintenance.By utilizing elemental selenium(Se)with a low melting point,easy sublimation,and multiple variable valence states,deep grain boundary modification was implemented inside the particles.The performance of the cathode material was evaluated through pouch cells,and the improvement mechanism was explored through molecular dynamics simulation calculations.Under the protection of a three-dimensional Se-rich modified layer,LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)achieved stable operation at ultrahigh voltages(4.6 V vs.Li/Li^(+));a sacrificial protection mechanism based on the chronic decomposition of the Se-rich layer was proposed to explain the efficacy of Se modification in stabilizing ternary materials.This deep grain boundary modification based on elemental Se provides a new solution for the ultrahigh-voltage operation of transition metal oxides and provides a scientific basis and technical support for solving the interface contact problem of all-solid-state batteries.
基金supported by the National Natural Science Foundation of China(51977069)the National Natural Science Foundation Youth Project of China(52107195)the First Key Research and JieBang Headed Program,Hunan Province,China(2021GK1250).
文摘Switched-capacitor/flying capacitor(FC)based multilevel converters have been gaining higher attention for their voltage-boosting ability.This feature makes them an attractive solution for renewable energy systems,such as low-voltage input photovoltaic power systems and electric vehicle systems.However,they usually require more high voltage rating switches and flying capacitors along with boosting capability.Furthermore,they suffer from high pulse currents at the switching transients.Aiming to solve these issues,this article proposes a new self-balancing three-phase five-level inverter based on the switched-capacitor(5L-SCTPNPC),which reduces the dc voltage requirement.The number of active switches is relatively smaller and seven active switches are required per phase.Especially,a soft-charging circuit for FC is designed to limit the impulse charging current.Compared to conventional multilevel inverters,the proposed five-level inverter reduces dc bus voltage by 50%.Significantly,the voltage stress of FC and the switches in parallel with FC are all reduced by 50%in comparison with some existing similar boosting five-level active-neutral-point-clamped(5L-BANPC)inverters.The operating principles,modulation strategy,and the design of the FC and charging inductor are provided in detailly.A comprehensive comparison study has been made to highlight the merits of the proposed inverter.Finally,the simulations and experiments validate the feasibility of the proposed topology.
基金supported in part by the National Natural Science Foundation of China(No.52177109)Key R&D Program of Hubei Province,China(No.2020BAB109).
文摘With the prevalence of renewable distributed energy resources(DERs)such as photovoltaics(PVs),modern active distribution networks(ADNs)suffer from voltage deviation and power quality issues.However,traditional voltage control methods often face a trade-off between efficiency and effectiveness,and rarely ensure robust voltage safety under typical state perturbations in practical distribution grids.In this paper,a robust model-free voltage regulation approach is proposed which simultaneously takes security and robustness into account.In this context,the voltage control problem is formulated as a constrained Markov decision process(CMDP).A safety-augmented multiagent deep deterministic policy gradient(MADDPG)algorithm is the trained to enable real-time collaborative optimization of ADNs,aiming to maintain nodal voltages within safe operational limits while minimizing total line losses.Moreover,a robust regulation loss is introduced to ensure reliable performance under various state perturbations in practical voltage controls.The proposed regulation algorithm effectively balance efficiency,safety,and robustness,and also demonstrates potential for generalizing these characteristics to other applications.Numerical studies vali-date the robustness of the proposed method under varying state perturbations on the IEEE test cases and the optimal integrated control performance when compared to other benchmarks.
基金supported in part by Smart Grid-National Science and Technology Major Project(No.2024ZD0801400)Science and technology projects of State Grid Corporation of China(No.52272224000V).
文摘The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the DCV transient behavior of a PLL-based DFIG system under asymmetrical grid faults.First,by considering the coupling characteristics of positive and negative sequence(PNS)components,a nonlinear largesignal model of DCV is developed.Furthermore,the transient characteristics of DCV under varying parameters are analyzed using phase trajectory diagrams.In addition,the transient stability(TS)mechanism of DCV during asymmetrical faults is examined through an en-ergy function approach.The analysis indicates that the transient instability of DCV is primarily associated with the control characteristics of PNS PLLs,while the TS level of DCV is mainly determined by the power coordination control between the rotor side converter and grid side converter.Moreover,a coordinated control strategy is proposed to enhance the TS of DCV under asymmet-rical grid faults.Finally,both simulation and experimental results are presented to validate the theoretical analysis and the effectiveness of the proposed strategy.
基金supported by the National Key Research and Development Program of China(No.2021YFB1507001).
文摘During sending-end faults in the hybrid cascaded HVDC(HC-HVDC)system,the transient voltage drop characteristics under the interaction of the AC/DC hybrid system remain unclear,and the reactive power support provided by the HC-HVDC to the sending-end AC system requires further investigation.To address this problem,the reactive power interaction coupling mechanism between the sending-end AC system and the HC-HVDC is revealed,and the transient voltage mathematical model considering fault severity and duration is established.Under the dynamic change of the AC system voltage,the difference between the reactive power provided only by the reactive power compensation devices and by the combined modular multilevel converters(MMC)and reactive power compensation devices is analyzed.It is concluded that using MMC to provide a proportion of reactive power enhances the reactive power support to the AC system during faults.Then,the transient voltage model considering the reactive power support of MMC is established,and the critical reactive power consumption of line commutated converter(LCC)is quantified.It is concluded that the reactive power consumption of LCC exceeding its critical value deteriorates the transient voltage.A coordinated support strategy for the sending-end AC system based on reactive power support of MMC and reactive power regulation of LCC is proposed.It can effectively address the challenge of weakened reactive power support to the AC system due to voltage drop,thereby preventing the unbalanced reactive power from deteriorating the transient voltage,and realizing active support of the tran-sient voltage.Finally,a simulation model is established on the PSCAD/EMTDC platform,and the simulation results validate the effectiveness of the proposed strategy in supporting the transient voltage,under different fault types,durations,severities,and locations.
基金The financial supports from National Natural Science Foundation of China(Nos.52574313,52204272 and 52074091)to this project。
文摘The susceptibility of ore particles to electrical breakdown plays a critical role for high voltage pulse(HVP)breakage,yet its quantitative characterization still lacks deep understanding.Two indicators,namely breakdown delay time(T_(d))and breakdown strength(E_(b))were compared,based on analysis on the two breakdown modes namely wavefront mode and post-wave mode.It was found that T_(d) is more suitable to characterize the susceptibility of ore particles to electrical breakdown in HVP breakage than E_(b).A probabilistic model based on the Weibull distribution is developed to describe the relation of breakdown probability to T_(d).Regression analyses were conducted to investigate how operating parameters and particle properties influence Td and size reduction degree of ore particles in HVP breakage.The regressed models demonstrate potential capability to predict metallic minerals content and HVP breakage degree based on operating parameters and particle properties.
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 in part by the National Natural Science Foundation of China under Grant 52477060in part by the Tianjin Natural Science Foundation Project under Grant 24JCZDJC00250in part by the Zhejiang Leading Innovation and Entrepreneurship Team Project under Grant 2024R01012.
文摘In position-sensorless brushless direct current(DC)motors(BLDCMs)fed by a four-switch three-phase(FSTP)inverter,only two phases are fully controlled,while the remaining phase is tied to the midpoint of the split DC-link capacitors.The voltage pulses required by inductance-based initial position detection can cause unequal discharge of the series capacitors,shifting the neutral-point voltage away from half of DC-link voltage(U_(dc)/2).This neutral-point drift breaks the spatial symmetry of the inverter voltage vectors,so the 360°electrical period can no longer be evenly partitioned into six sectors during initial rotor position detection.To address this issue,this paper proposes a detection-pulse injection sequence that explicitly accounts for the asymmetric voltage vectors of the FSTP inverter.With the proposed sequence,the initial rotor position can be identified within a 30°electrical sector.The method requires no additional voltage or current sensors,and experimental results confirm its feasibility.
文摘Severe injuries due to electricity are rare,but when they occur,they may cause life-threatening conditions.In order to define the severity of electrical injuries,the most widely used classification is voltage power.Injuries are mainly classified into two categories as low voltage electrical injuries(LVEI)(<1000 V)and high voltage electrical injuries(>1000 V).Fatal injuries have been reported mostly after high-voltage electric shock.Low-voltage electricity current rarely causes severe trauma and complications.
文摘With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.
基金supported by the National Key Laboratory of Materials Behavior and Evaluation Technology in Space Environment(No.6142910220208)National Natural Science Foundation of China(Nos.12105341 and 12035019)the opening fund of Key Laboratory of Silicon Device and Technology,Chinese Academy of Sciences(No.KLSDTJJ2022-3).
文摘This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) under high linear energy transfer heavyion experimentation.The experimental findings demonstrate that applying a negative back-gate bias to NMOS and a positive back-gate bias to PMOS enhances the SEU resistance of SRAM.Specifically,as the back-gate bias for N-type transistors(V_(nsoi)) decreases from 0 to-10 V,the SEU cross section decreases by 93.23%,whereas an increase in the back-gate bias for P-type transistors (V_(psoi)) from 0 to 10 V correlates with an 83.7%reduction in SEU cross section.Furthermore,a significant increase in the SEU cross section was observed with increase in supply voltage,as evidenced by a 159%surge at V_(DD)=1.98 V compared with the nominal voltage of 1.8 V.To explore the physical mechanisms underlying these experimental data,we analyzed the dependence of the critical charge of the circuit and the collected charge on the bias voltage by simulating SEUs using technology computer-aided design.
文摘Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage transformer errors, particularly minor variations in multi-channel setups, remains challenging. This paper proposes a method for online error tracking of multi-channel capacitive voltage transformers using a Co-Prediction Matrix. The approach leverages the strong correlation between in-phase channels, particularly the invariance of the signal proportions among them. By establishing a co-prediction matrix based on these proportional relationships, The influence of voltage changes on the primary measurements is mitigated. Analyzing the relationships between the co-prediction matrices over time allows for inferring true measurement errors. Experimental validation with real-world data confirms the effectiveness of the method, demonstrating its capability to continuously track capacitive voltage transformer measurement errors online with precision over extended durations.
