Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operati...Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.展开更多
The load types in low-voltage distribution systems are diverse.Some loads have current signals that are similar to series fault arcs,making it difficult to effectively detect fault arcs during their occurrence and sus...The load types in low-voltage distribution systems are diverse.Some loads have current signals that are similar to series fault arcs,making it difficult to effectively detect fault arcs during their occurrence and sustained combustion,which can easily lead to serious electrical fire accidents.To address this issue,this paper establishes a fault arc prototype experimental platform,selects multiple commonly used loads for fault arc experiments,and collects data in both normal and fault states.By analyzing waveform characteristics and selecting fault discrimination feature indicators,corresponding feature values are extracted for qualitative analysis to explore changes in timefrequency characteristics of current before and after faults.Multiple features are then selected to form a multidimensional feature vector space to effectively reduce arc misjudgments and construct a fault discrimination feature database.Based on this,a fault arc hazard prediction model is built using random forests.The model’s multiple hyperparameters are simultaneously optimized through grid search,aiming tominimize node information entropy and complete model training,thereby enhancing model robustness and generalization ability.Through experimental verification,the proposed method accurately predicts and classifies fault arcs of different load types,with an average accuracy at least 1%higher than that of the commonly used fault predictionmethods compared in the paper.展开更多
The electrical design of high-rise buildings usually involves many links, among which the low-voltage distribution system plays an irreplaceable role. From the current domestic development, high-rise buildings mainly ...The electrical design of high-rise buildings usually involves many links, among which the low-voltage distribution system plays an irreplaceable role. From the current domestic development, high-rise buildings mainly refer to buildings with more than 30 floors. At the same time, with the rise of the floor height, the complexity of the electrical system will increase significantly, which makes the electrical design face many difficulties. In the actual process of high-rise building electrical design, it is not only necessary to comprehensively control the reliability of the building power supply system, but also to ensure that the electrical devices can play an effective role. Therefore, in-depth study of low-voltage distribution system has practical significance. This paper analyzes the actual electrical design of high-rise buildings, discusses the stability and safety of the system, and explores how to better construct the electrical design scheme and apply it in practice, so as to lay a solid foundation for the construction of high-rise buildings.展开更多
This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also ...This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also tracking the system optimum power point; the system optimum power point is the maximum power drawn from the series-connected power sources while their voltages are kept uniformly distributed. With proper uniform input voltage distribution control, near maximum use of the power sources is achieved by employing only one MPT （maximum power tracking） controller instead of multiple MPT controllers dedicated for their respective power sources. Provided that the maximum power point voltages of the input power sources are similar, the resulting system architecture offers near-maximum power transfer with a lower parts count. A feasibility study using computer simulation has successfully validated two SIPO power architectures and their control concepts for optimum power transfer.展开更多
At present, along with the infrastructure construction in our country to the development trend of China's urbanization goal just around the corner, people use electricity demand increase, under this background, th...At present, along with the infrastructure construction in our country to the development trend of China's urbanization goal just around the corner, people use electricity demand increase, under this background, the power problem also gradually to increase, low voltage distribution circuit design research is an important part of the normal distribution system in China. In the design process of low-voltage distribution line, we should strictly follow the national regulations to ensure the scientific and reasonable design of the line and the implementation of its degree of implementation. This concerns the national economy and people's livelihood and is a guarantee for people's happiness. Therefore, the problems existing in the design of low-voltage distribution lines in China's power system are studied and analyzed, and some ideas are put forward for reference.展开更多
With the development of society, China's economy is growing rapidly. With the gradual improvement of people's living standards, electricity has become an indispensable part of our lives, affecting people's...With the development of society, China's economy is growing rapidly. With the gradual improvement of people's living standards, electricity has become an indispensable part of our lives, affecting people's lives and the development of the national economy all the time.展开更多
To adapt to the uncertainty of new energy,increase new energy consumption,and reduce carbon emissions,a high-voltage distribution network energy storage planning model based on robustness-oriented planning and distrib...To adapt to the uncertainty of new energy,increase new energy consumption,and reduce carbon emissions,a high-voltage distribution network energy storage planning model based on robustness-oriented planning and distributed new energy consumption is proposed.Firstly,the spatio-temporal correlation of large-scale wind-photovoltaic energy is modeled based on the Vine Copula model,and the spatial correlation of the generated wind-photovoltaic power generation is corrected to get the spatio-temporal correlation of wind-photovoltaic power generation scenarios.Finally,considering the subsequent development of new energy on demand for high-voltage distribution network peaking margin and the economy of the system peaking,we propose the optimization model of high-voltage distribution network energy storage plant siting and capacity setting for source-storage cooperative peaking.The simulation results show that the proposed energy storage plant planning method can effectively alleviate the branch circuit blockage,promote new energy consumption,reduce the burden of the main grid peak shifting,and leave sufficient peak shifting margin for the subsequent development of a new energy distribution network while ensuring the economy.展开更多
The power loss minimization and DC voltage stability of the multi-terminal direct current(MTDC)system with large-scale wind farm(WF)cluster affect the stability and power quality of the interconnected power grid.This ...The power loss minimization and DC voltage stability of the multi-terminal direct current(MTDC)system with large-scale wind farm(WF)cluster affect the stability and power quality of the interconnected power grid.This paper proposes a distributed optimal voltage control(DOVC)strategy,which aims to optimize voltage distribution in MTDC and WF systems,reduce system power losses,and track power dispatch commands.The proposed DOVC strategy employs a bi-level distributed control architecture.At the upper level,the MTDC controller coordinates power flow,DC-side voltage of grid-side voltage source converters(GSVSCs),and WF-side voltage source converters(WFVSCs)for power loss minimization and DC voltage stabilization of the MTDC system.At the lower level,the WF controller coordinates the controlled bus voltage of WFVSC and the active and reactive power of wind turbines(WTs)to maintain WT terminal voltages within feasible range.Then,the WF controller minimizes the power loss of the WF system,while tracking the optimal command from the upper-level control strategy.Considering the computational tasks of multi-objective optimization with large-scale WF cluster,the proposed DOVC strategy is executed in a distributed manner based on the alternating direction method of multipliers(ADMM).An MTDC system with large-scale WF cluster is established in MATLAB to validate the effectiveness of the proposed DOVC strategy.展开更多
In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past...In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.展开更多
All-dielectric self-supporting(ADSS) cables are installed along with transmission line for the purpose of communication.During installation the outer layer of the cable is hydrophobic and is not prone to dry band arci...All-dielectric self-supporting(ADSS) cables are installed along with transmission line for the purpose of communication.During installation the outer layer of the cable is hydrophobic and is not prone to dry band arcing. These cables become less hydrophobic over time and become vulnerable to dry band arcing.This loss in hydrophobicity is because of the contamination formed on the outer layer due to pollution.This is one of the reasons which cause cable failure.Considerable amount of losses will be incurred on the occurrence of a cable failure as the cables are also leased to other companies.An improved equivalent circuit is used to calculate the voltage and current distribution of the double circuit line.A three-phase single circuit line and a three-phase double circuit line are used to calculate their corresponding voltage distribution and current distribution.The results could be used to predict dry band arcing on similar models.The method used considers sag,span and pollution on ADSS cable.展开更多
The inconsistency of lithium-ion cells degrades battery performance,lifetime and even safety.The complexity of the cell reaction mechanism causes an irregular asymmetrical distribution of various cell parameters,such ...The inconsistency of lithium-ion cells degrades battery performance,lifetime and even safety.The complexity of the cell reaction mechanism causes an irregular asymmetrical distribution of various cell parameters,such as capacity and internal resistance,among others.In this study,the Newman electrochemical model was used to simulate the 1 C discharge curves of 100 LiMn2 O4 pouch cells with parameter variations typically produced in manufacturing processes,and the three-parameter Weibull probability model was used to analyze the dispersion and symmetry of the resulting discharge voltage distributions.The results showed that the dispersion of the voltage distribution was related to the rate of decrease in the discharge voltage,and the symmetry was related to the change in the rate of voltage decrease.The effect of the cells’capacity dominated the voltage distribution thermodynamically during discharge,and the phase transformation process significantly skewed the voltage distribution.The effects of the ohmic drop and polarization voltage on the voltage distribution were primarily kinetic.The presence of current returned the right-skewed voltage distribution caused by phase transformation to a more symmetrical distribution.Thus,the Weibull parameters elucidated the electrochemical behavior during the discharge process,and this method can guide the prediction and control of cell inconsistency,as well as detection and control strategies for cell management systems.展开更多
The capacitive reactive power reversal in the urban distribution grid is increasingly prominent at the period of light load in the last years.In severe cases,it will endanger the security and stability of power grid.T...The capacitive reactive power reversal in the urban distribution grid is increasingly prominent at the period of light load in the last years.In severe cases,it will endanger the security and stability of power grid.This paper presents an optimal reactive power compensation method of distribution network to prevent reactive power reverse.Firstly,an integrated reactive power planning(RPP)model with power factor constraints is established.Capacitors and reactors are considered to be installed in the distribution system at the same time.The objective function is the cost minimization of compensation and real power loss with transformers and lines during the planning period.Nodal power factor limits and reactor capacity constraints are new constraints.Then,power factor sensitivity with respect to reactive power is derived.An improved genetic algorithm by power factor sensitivity is used to solve the model.The optimal locations and sizes of reactors and capacitors can avoid reactive power reversal and power factor exceeding the limit.Finally,the effectiveness of the model and algorithm is proven by a typical high-voltage distribution network.展开更多
Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigatio...Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigation of a typical 750 kV AC substation located in Lanzhou with ultraviolet imager(UVI) demonstrated that the corona discharge of some insulators is serious due to the improper structure design and installation,so research on porcelain insulators used in substation is needed.The three-dimensional finite element method(FEM) 750 kV AC substation calculation model was established to calculate electric field and voltage distribution of insulators,and the voltage distribution curves along insulators which are classified by type and suspension location were obtained using a novel FEM method which can effectively reduce the calculation amount without losing accuracy,meanwhile,the effect of the grading ring for improving voltage distribution of insulators was studied by adjusting the structure parameters of grading ring. Consequently,an optimization structure of rings was proposed by improving the voltage distribution of insulator string and reducing the electric strength of grading ring for the purpose of restricting corona noise,and the onsite observations by UVI showed that the newly manufactured and installed grading ring could obviously avoid the occurrences of corona discharge which validates the optimization design.This paper proposed an effective method combining UVI observation and FEM calculation to study voltage-sharing characteristics of porcelain insulators,and the results can provide experiences and references for the design of 750 kV AC substation.展开更多
Distribution networks are commonly used to demonstrate low-voltage problems.A new method to improve voltage quality is using battery energy storage stations(BESSs),which has a four-quadrant regulating capacity.In this...Distribution networks are commonly used to demonstrate low-voltage problems.A new method to improve voltage quality is using battery energy storage stations(BESSs),which has a four-quadrant regulating capacity.In this paper,an optimal dispatching model of a distributed BESS considering peak load shifting is proposed to improve the voltage distribution in a distribution network.The objective function is to minimize the power exchange cost between the distribution network and the transmission network and the penalty cost of the voltage deviation.In the process,various constraints are considered,including the node power balance,single/two-way power flow,peak load shifting,line capacity,voltage deviation,photovoltaic station operation,main transformer capacity,and power factor of the distribution network.The big M method is used to linearize the nonlinear variables in the objective function and constraints,and the model is transformed into a mixed-integer linear programming problem,which significantly improves the model accuracy.Simulations are performed using the modified IEEE 33-node system.A typical time period is selected to analyze the node voltage variation,and the results show that the maximum voltage deviation can be reduced from 14.06%to 4.54%.The maximum peak-valley difference of the system can be reduced from 8.83 to 4.23 MW,and the voltage qualification rate can be significantly improved.Moreover,the validity of the proposed model is verified through simulations.展开更多
Accurate topological information is crucial in supporting the coordinated operational requirements of source-load-storage in low-voltage distribution networks.Comprehensive coverage of smart meters provides a database...Accurate topological information is crucial in supporting the coordinated operational requirements of source-load-storage in low-voltage distribution networks.Comprehensive coverage of smart meters provides a database for low-voltage topology identification(LVTI).However,because of electricity theft,power line commu-nication crosstalk,and interruption of communication,the measurement data may be distorted.This can seriously affect the performance of LVTI methods.Thus,this paper defines hidden errors and proposes an LVTI method based on layer-by-layer stepwise regression.In the first step,a multi-linear regression model is developed for consumer-branch connectivity identification based on the energy conservation principle.In the second step,a significance factor based on the t-test is proposed to modify the identification results by considering the hidden errors.In the third step,the regression model and significance threshold parameters are iteratively updated layer by layer to improve the recall rate of the final identification results.Finally,simulations of a test system with 63 users are carried out,and the practical application results show that the proposed method can guarantee over 90%precision under the influence of hidden errors.展开更多
This paper presents a new method for the calculation of the transient voltage distribution over a transformer winding——the Bergeron's method. Using the nodal admittance matrix, formulae are developed for the re...This paper presents a new method for the calculation of the transient voltage distribution over a transformer winding——the Bergeron's method. Using the nodal admittance matrix, formulae are developed for the resistances, and self and mutual inductances of the equivalent circuit. Calculated results are given. The method reduces internal memory requirement, allows easy formation of the nodal admittance matrix, reduces computational time, etc.展开更多
A high current RFQ （radio frequency quadrupole） is being studied at the Institute of Modern Physics, CAS for the direct plasma injection scheme. Shunt impedance is an important parameter when designing a ＆rod RFQ c...A high current RFQ （radio frequency quadrupole） is being studied at the Institute of Modern Physics, CAS for the direct plasma injection scheme. Shunt impedance is an important parameter when designing a ＆rod RFQ cavity, it reflects the RF efficiency of the cavity, and has a direct influence on the cost of the structure. Voltage distribution of a RFQ cavity has an effect on beam transmission, and particles would be lost if the actual voltage distribution is not as what it should be. The influence of cell length, stem thickness and height on shunt impedance and voltage distribution have been studied, in particular the effect of projecting electrodes has been investigated in detail.展开更多
Voltage distribution in windings is important for inverter-fed traction motors.The analysis on voltage distribution characteristics is significant to the study of insulation failure mechanisms and structure design.Fir...Voltage distribution in windings is important for inverter-fed traction motors.The analysis on voltage distribution characteristics is significant to the study of insulation failure mechanisms and structure design.First,a distribution parameter model has been developed according to the winding structure of an inverter-fed traction motor.Based on the model,finite element differential method was employed to determine voltage distribution characteristics.Simulation results were compared with actual voltage distribution.Moreover,the influence of pulse rise time and cable was discussed.The results show that the shorter the pulse rise time is,the more uneven the voltage distribution is.In addition,cable length has little influence on voltage distribution characteristics.However,the amplitude of voltage would also increase by 40%in coils and turns.展开更多
Aimed at solving the problem of optimal planning for high voltage distribution substations,an efficient method is put forward.The method divides the problem into two sub-problems:source locating and combina tional opt...Aimed at solving the problem of optimal planning for high voltage distribution substations,an efficient method is put forward.The method divides the problem into two sub-problems:source locating and combina tional optimization.The algorithm of allocating and locating alternatively(ALA)is widely used to deal with the source lo cating problem,but it is dependent on the initial location to a large degree.Thus,some modifications were made to the ALA algorithm,which could greatly improve the quality of solutions.In addition,considering the non-convex and nonconcave nature of the sub-problem of combinational optimization,the branch-and-bound technique was adopted to obtain or approximate a global optimal solution.To improve the efficiency of the branch-and-bound technique,some heuristic principles were proposed to cut those branches that may generate a global optimization solution with low probability.Examples show that the proposed algorithm meets the requirement of engineering and it is an effective approach to rapidly solve the problem of optimal planning for high voltage distribution substations.展开更多
This research focuses on restructuring medium-level voltage(MLV)distribution systems by integrating distributed renewable energy resources(DER)at multiple feed points.It examines the impact of incorporating renewable ...This research focuses on restructuring medium-level voltage(MLV)distribution systems by integrating distributed renewable energy resources(DER)at multiple feed points.It examines the impact of incorporating renewable energy and evaluates system performance metrics such as robustness,static voltage stability,line carrying capacity,utility grid effectiveness,and losses within the conventional radial distribution framework commonly used in educational institutions.The contingency ranking of the real-time radial distribution system(RTRDS)for a typical educational institution consisting of N buses was conducted.Parameters such as the Voltage Performance Index(PIV)and Flow Performance Index(PIF)were evaluated.The results support the integration of distributed renewable energy sources within the existing radial distribution grid infrastructure.This research proposes enhanced contingency analyses through a straightforward reconfiguration process involving an additional tie line(Nþ1)for the existing N bus radial distribution system(RDS).Load flow analysis of the RDS with distributed renewable energy resources(DER)for both N bus and Nþ1 bus systems was conducted using the Gauss-Seidel and Newton–Raphson methods.Simulation results indicate that baseline loading is consistently maintained by grid sources and DER sources connected at multiple feed points.The proposed configuration of the Nþ1 bus system for the existing RTRDS was evaluated for voltage performance and compared with the Grey Wolf Optimization(GWO)algorithm.The results indicate that the Nþ1 bus configuration modeled using the MiPower tool performed comparably to the GWO results.Additionally,the contingency ranking for the proposed Nþ1 configuration was validated using the IEEE 10 and 30 bus system.展开更多
基金supported by the National Key Rese arch and Development Program of China(2018YFB0904100)Science and Technology Project of State Grid(SGHB0000KXJS1800685)
文摘Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.
基金This work was funded by Beijing Key Laboratory of Distribution Transformer Energy-Saving Technology(China Electric Power Research Institute).
文摘The load types in low-voltage distribution systems are diverse.Some loads have current signals that are similar to series fault arcs,making it difficult to effectively detect fault arcs during their occurrence and sustained combustion,which can easily lead to serious electrical fire accidents.To address this issue,this paper establishes a fault arc prototype experimental platform,selects multiple commonly used loads for fault arc experiments,and collects data in both normal and fault states.By analyzing waveform characteristics and selecting fault discrimination feature indicators,corresponding feature values are extracted for qualitative analysis to explore changes in timefrequency characteristics of current before and after faults.Multiple features are then selected to form a multidimensional feature vector space to effectively reduce arc misjudgments and construct a fault discrimination feature database.Based on this,a fault arc hazard prediction model is built using random forests.The model’s multiple hyperparameters are simultaneously optimized through grid search,aiming tominimize node information entropy and complete model training,thereby enhancing model robustness and generalization ability.Through experimental verification,the proposed method accurately predicts and classifies fault arcs of different load types,with an average accuracy at least 1%higher than that of the commonly used fault predictionmethods compared in the paper.
文摘The electrical design of high-rise buildings usually involves many links, among which the low-voltage distribution system plays an irreplaceable role. From the current domestic development, high-rise buildings mainly refer to buildings with more than 30 floors. At the same time, with the rise of the floor height, the complexity of the electrical system will increase significantly, which makes the electrical design face many difficulties. In the actual process of high-rise building electrical design, it is not only necessary to comprehensively control the reliability of the building power supply system, but also to ensure that the electrical devices can play an effective role. Therefore, in-depth study of low-voltage distribution system has practical significance. This paper analyzes the actual electrical design of high-rise buildings, discusses the stability and safety of the system, and explores how to better construct the electrical design scheme and apply it in practice, so as to lay a solid foundation for the construction of high-rise buildings.
文摘This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also tracking the system optimum power point; the system optimum power point is the maximum power drawn from the series-connected power sources while their voltages are kept uniformly distributed. With proper uniform input voltage distribution control, near maximum use of the power sources is achieved by employing only one MPT （maximum power tracking） controller instead of multiple MPT controllers dedicated for their respective power sources. Provided that the maximum power point voltages of the input power sources are similar, the resulting system architecture offers near-maximum power transfer with a lower parts count. A feasibility study using computer simulation has successfully validated two SIPO power architectures and their control concepts for optimum power transfer.
文摘At present, along with the infrastructure construction in our country to the development trend of China's urbanization goal just around the corner, people use electricity demand increase, under this background, the power problem also gradually to increase, low voltage distribution circuit design research is an important part of the normal distribution system in China. In the design process of low-voltage distribution line, we should strictly follow the national regulations to ensure the scientific and reasonable design of the line and the implementation of its degree of implementation. This concerns the national economy and people's livelihood and is a guarantee for people's happiness. Therefore, the problems existing in the design of low-voltage distribution lines in China's power system are studied and analyzed, and some ideas are put forward for reference.
文摘With the development of society, China's economy is growing rapidly. With the gradual improvement of people's living standards, electricity has become an indispensable part of our lives, affecting people's lives and the development of the national economy all the time.
基金supported by State Grid Anhui Electric Power Co.,Ltd.Research Program(B3120923000C).
文摘To adapt to the uncertainty of new energy,increase new energy consumption,and reduce carbon emissions,a high-voltage distribution network energy storage planning model based on robustness-oriented planning and distributed new energy consumption is proposed.Firstly,the spatio-temporal correlation of large-scale wind-photovoltaic energy is modeled based on the Vine Copula model,and the spatial correlation of the generated wind-photovoltaic power generation is corrected to get the spatio-temporal correlation of wind-photovoltaic power generation scenarios.Finally,considering the subsequent development of new energy on demand for high-voltage distribution network peaking margin and the economy of the system peaking,we propose the optimization model of high-voltage distribution network energy storage plant siting and capacity setting for source-storage cooperative peaking.The simulation results show that the proposed energy storage plant planning method can effectively alleviate the branch circuit blockage,promote new energy consumption,reduce the burden of the main grid peak shifting,and leave sufficient peak shifting margin for the subsequent development of a new energy distribution network while ensuring the economy.
基金supported by the National Key R&D Program of China(No.2022YFF0608700).
文摘The power loss minimization and DC voltage stability of the multi-terminal direct current(MTDC)system with large-scale wind farm(WF)cluster affect the stability and power quality of the interconnected power grid.This paper proposes a distributed optimal voltage control(DOVC)strategy,which aims to optimize voltage distribution in MTDC and WF systems,reduce system power losses,and track power dispatch commands.The proposed DOVC strategy employs a bi-level distributed control architecture.At the upper level,the MTDC controller coordinates power flow,DC-side voltage of grid-side voltage source converters(GSVSCs),and WF-side voltage source converters(WFVSCs)for power loss minimization and DC voltage stabilization of the MTDC system.At the lower level,the WF controller coordinates the controlled bus voltage of WFVSC and the active and reactive power of wind turbines(WTs)to maintain WT terminal voltages within feasible range.Then,the WF controller minimizes the power loss of the WF system,while tracking the optimal command from the upper-level control strategy.Considering the computational tasks of multi-objective optimization with large-scale WF cluster,the proposed DOVC strategy is executed in a distributed manner based on the alternating direction method of multipliers(ADMM).An MTDC system with large-scale WF cluster is established in MATLAB to validate the effectiveness of the proposed DOVC strategy.
基金supported by the Beijing Natural Science Foundation(No.QY24166).
文摘In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.
文摘All-dielectric self-supporting(ADSS) cables are installed along with transmission line for the purpose of communication.During installation the outer layer of the cable is hydrophobic and is not prone to dry band arcing. These cables become less hydrophobic over time and become vulnerable to dry band arcing.This loss in hydrophobicity is because of the contamination formed on the outer layer due to pollution.This is one of the reasons which cause cable failure.Considerable amount of losses will be incurred on the occurrence of a cable failure as the cables are also leased to other companies.An improved equivalent circuit is used to calculate the voltage and current distribution of the double circuit line.A three-phase single circuit line and a three-phase double circuit line are used to calculate their corresponding voltage distribution and current distribution.The results could be used to predict dry band arcing on similar models.The method used considers sag,span and pollution on ADSS cable.
基金financially supported by the National Natural Science Foundation of China(No.U156405)the GRINM Youth Foundation funded project
文摘The inconsistency of lithium-ion cells degrades battery performance,lifetime and even safety.The complexity of the cell reaction mechanism causes an irregular asymmetrical distribution of various cell parameters,such as capacity and internal resistance,among others.In this study,the Newman electrochemical model was used to simulate the 1 C discharge curves of 100 LiMn2 O4 pouch cells with parameter variations typically produced in manufacturing processes,and the three-parameter Weibull probability model was used to analyze the dispersion and symmetry of the resulting discharge voltage distributions.The results showed that the dispersion of the voltage distribution was related to the rate of decrease in the discharge voltage,and the symmetry was related to the change in the rate of voltage decrease.The effect of the cells’capacity dominated the voltage distribution thermodynamically during discharge,and the phase transformation process significantly skewed the voltage distribution.The effects of the ohmic drop and polarization voltage on the voltage distribution were primarily kinetic.The presence of current returned the right-skewed voltage distribution caused by phase transformation to a more symmetrical distribution.Thus,the Weibull parameters elucidated the electrochemical behavior during the discharge process,and this method can guide the prediction and control of cell inconsistency,as well as detection and control strategies for cell management systems.
文摘The capacitive reactive power reversal in the urban distribution grid is increasingly prominent at the period of light load in the last years.In severe cases,it will endanger the security and stability of power grid.This paper presents an optimal reactive power compensation method of distribution network to prevent reactive power reverse.Firstly,an integrated reactive power planning(RPP)model with power factor constraints is established.Capacitors and reactors are considered to be installed in the distribution system at the same time.The objective function is the cost minimization of compensation and real power loss with transformers and lines during the planning period.Nodal power factor limits and reactor capacity constraints are new constraints.Then,power factor sensitivity with respect to reactive power is derived.An improved genetic algorithm by power factor sensitivity is used to solve the model.The optimal locations and sizes of reactors and capacitors can avoid reactive power reversal and power factor exceeding the limit.Finally,the effectiveness of the model and algorithm is proven by a typical high-voltage distribution network.
文摘Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigation of a typical 750 kV AC substation located in Lanzhou with ultraviolet imager(UVI) demonstrated that the corona discharge of some insulators is serious due to the improper structure design and installation,so research on porcelain insulators used in substation is needed.The three-dimensional finite element method(FEM) 750 kV AC substation calculation model was established to calculate electric field and voltage distribution of insulators,and the voltage distribution curves along insulators which are classified by type and suspension location were obtained using a novel FEM method which can effectively reduce the calculation amount without losing accuracy,meanwhile,the effect of the grading ring for improving voltage distribution of insulators was studied by adjusting the structure parameters of grading ring. Consequently,an optimization structure of rings was proposed by improving the voltage distribution of insulator string and reducing the electric strength of grading ring for the purpose of restricting corona noise,and the onsite observations by UVI showed that the newly manufactured and installed grading ring could obviously avoid the occurrences of corona discharge which validates the optimization design.This paper proposed an effective method combining UVI observation and FEM calculation to study voltage-sharing characteristics of porcelain insulators,and the results can provide experiences and references for the design of 750 kV AC substation.
基金This work was supported by the Science and Technology Project of State Grid Corporation of China“Intelligent Coordination Control and Energy Optimization Management of Super-large Scale Battery Energy Storage Power Station Based on Information Physics Fusion-Simulation Model and Transient Characteristics of Super-large Scale Battery Energy Storage Power Station”(No.DG71-18-009).
文摘Distribution networks are commonly used to demonstrate low-voltage problems.A new method to improve voltage quality is using battery energy storage stations(BESSs),which has a four-quadrant regulating capacity.In this paper,an optimal dispatching model of a distributed BESS considering peak load shifting is proposed to improve the voltage distribution in a distribution network.The objective function is to minimize the power exchange cost between the distribution network and the transmission network and the penalty cost of the voltage deviation.In the process,various constraints are considered,including the node power balance,single/two-way power flow,peak load shifting,line capacity,voltage deviation,photovoltaic station operation,main transformer capacity,and power factor of the distribution network.The big M method is used to linearize the nonlinear variables in the objective function and constraints,and the model is transformed into a mixed-integer linear programming problem,which significantly improves the model accuracy.Simulations are performed using the modified IEEE 33-node system.A typical time period is selected to analyze the node voltage variation,and the results show that the maximum voltage deviation can be reduced from 14.06%to 4.54%.The maximum peak-valley difference of the system can be reduced from 8.83 to 4.23 MW,and the voltage qualification rate can be significantly improved.Moreover,the validity of the proposed model is verified through simulations.
基金supported by the National Natural Sci-ence Foundation of China(No.52177085)Science and Technology Planning Project of Guangzhou(No.202102021208).
文摘Accurate topological information is crucial in supporting the coordinated operational requirements of source-load-storage in low-voltage distribution networks.Comprehensive coverage of smart meters provides a database for low-voltage topology identification(LVTI).However,because of electricity theft,power line commu-nication crosstalk,and interruption of communication,the measurement data may be distorted.This can seriously affect the performance of LVTI methods.Thus,this paper defines hidden errors and proposes an LVTI method based on layer-by-layer stepwise regression.In the first step,a multi-linear regression model is developed for consumer-branch connectivity identification based on the energy conservation principle.In the second step,a significance factor based on the t-test is proposed to modify the identification results by considering the hidden errors.In the third step,the regression model and significance threshold parameters are iteratively updated layer by layer to improve the recall rate of the final identification results.Finally,simulations of a test system with 63 users are carried out,and the practical application results show that the proposed method can guarantee over 90%precision under the influence of hidden errors.
文摘This paper presents a new method for the calculation of the transient voltage distribution over a transformer winding——the Bergeron's method. Using the nodal admittance matrix, formulae are developed for the resistances, and self and mutual inductances of the equivalent circuit. Calculated results are given. The method reduces internal memory requirement, allows easy formation of the nodal admittance matrix, reduces computational time, etc.
文摘A high current RFQ （radio frequency quadrupole） is being studied at the Institute of Modern Physics, CAS for the direct plasma injection scheme. Shunt impedance is an important parameter when designing a ＆rod RFQ cavity, it reflects the RF efficiency of the cavity, and has a direct influence on the cost of the structure. Voltage distribution of a RFQ cavity has an effect on beam transmission, and particles would be lost if the actual voltage distribution is not as what it should be. The influence of cell length, stem thickness and height on shunt impedance and voltage distribution have been studied, in particular the effect of projecting electrodes has been investigated in detail.
基金This work was supported by the National Natural Science Foundation of China(Grant No.50377035)Fok YindTung Education Foundation(No.91060).
文摘Voltage distribution in windings is important for inverter-fed traction motors.The analysis on voltage distribution characteristics is significant to the study of insulation failure mechanisms and structure design.First,a distribution parameter model has been developed according to the winding structure of an inverter-fed traction motor.Based on the model,finite element differential method was employed to determine voltage distribution characteristics.Simulation results were compared with actual voltage distribution.Moreover,the influence of pulse rise time and cable was discussed.The results show that the shorter the pulse rise time is,the more uneven the voltage distribution is.In addition,cable length has little influence on voltage distribution characteristics.However,the amplitude of voltage would also increase by 40%in coils and turns.
基金supported by the National Natural Science Foundation of China (Grant No.59877017).
文摘Aimed at solving the problem of optimal planning for high voltage distribution substations,an efficient method is put forward.The method divides the problem into two sub-problems:source locating and combina tional optimization.The algorithm of allocating and locating alternatively(ALA)is widely used to deal with the source lo cating problem,but it is dependent on the initial location to a large degree.Thus,some modifications were made to the ALA algorithm,which could greatly improve the quality of solutions.In addition,considering the non-convex and nonconcave nature of the sub-problem of combinational optimization,the branch-and-bound technique was adopted to obtain or approximate a global optimal solution.To improve the efficiency of the branch-and-bound technique,some heuristic principles were proposed to cut those branches that may generate a global optimization solution with low probability.Examples show that the proposed algorithm meets the requirement of engineering and it is an effective approach to rapidly solve the problem of optimal planning for high voltage distribution substations.
文摘This research focuses on restructuring medium-level voltage(MLV)distribution systems by integrating distributed renewable energy resources(DER)at multiple feed points.It examines the impact of incorporating renewable energy and evaluates system performance metrics such as robustness,static voltage stability,line carrying capacity,utility grid effectiveness,and losses within the conventional radial distribution framework commonly used in educational institutions.The contingency ranking of the real-time radial distribution system(RTRDS)for a typical educational institution consisting of N buses was conducted.Parameters such as the Voltage Performance Index(PIV)and Flow Performance Index(PIF)were evaluated.The results support the integration of distributed renewable energy sources within the existing radial distribution grid infrastructure.This research proposes enhanced contingency analyses through a straightforward reconfiguration process involving an additional tie line(Nþ1)for the existing N bus radial distribution system(RDS).Load flow analysis of the RDS with distributed renewable energy resources(DER)for both N bus and Nþ1 bus systems was conducted using the Gauss-Seidel and Newton–Raphson methods.Simulation results indicate that baseline loading is consistently maintained by grid sources and DER sources connected at multiple feed points.The proposed configuration of the Nþ1 bus system for the existing RTRDS was evaluated for voltage performance and compared with the Grey Wolf Optimization(GWO)algorithm.The results indicate that the Nþ1 bus configuration modeled using the MiPower tool performed comparably to the GWO results.Additionally,the contingency ranking for the proposed Nþ1 configuration was validated using the IEEE 10 and 30 bus system.
