In this paper,the explicit state-space model for a multi-inverter system including grid-following inverter-based generators(IBGs)and grid-forming IBGs is developed by the two-level component connection method(CCM),whi...In this paper,the explicit state-space model for a multi-inverter system including grid-following inverter-based generators(IBGs)and grid-forming IBGs is developed by the two-level component connection method(CCM),which modularized inverter control blocks at the primary level and IBGs at the secondary level.Based on the comprehensive state-space model representing full order of system dynamics,eigenvalues of the overall system are thoroughly analyzed,identifying potential adverse impacts of not only grid-following inverters,but also grid forming inverters on the system small-signal stability,with the underlying principle of oscillations also understood.Numerical and simulation results validate effectiveness of the proposed methodology on IEEE benchmarking 39-bus system.展开更多
This paper presents a finite-time economic model predictive control(MPC)algorithm that can be used for frequency regulation and optimal load dispatch in multi-area power systems.Economic MPC can be used in a power sys...This paper presents a finite-time economic model predictive control(MPC)algorithm that can be used for frequency regulation and optimal load dispatch in multi-area power systems.Economic MPC can be used in a power system to ensure frequency stability,real-time economic optimization,control of the system and optimal load dispatch from it.A generalized terminal penalty term was used,and the finite-time convergence of the system was guaranteed.The effectiveness of the proposed model predictive control algorithm was verified by simulating a power system,which had two areas connected by an AC tie line.The simulation results demonstrated the effectiveness of the algorithm.展开更多
Since mechanical loads exert a significant influence on the life span of wind turbines, the reduction of transient load on drive-train shaft has received more attention when implementing a maximum power point tracking...Since mechanical loads exert a significant influence on the life span of wind turbines, the reduction of transient load on drive-train shaft has received more attention when implementing a maximum power point tracking(MPPT) controller.Moreover, a trade-off between the efficiency of wind energy extraction and the load level of drive-train shaft becomes a key issue. However, for the existing control strategies based on nonlinear model of wind turbines, the MPPT efficiencies are improved at the cost of the intensive fluctuation of generator torque and significant increase of transient load on drive train shaft. Hence, in this paper, a nonlinear controller with variable parameter is proposed for improving MPPT efficiency and mitigating transient load on drive-train simultaneously. Then,simulations on FAST(Fatigue, Aerodynamics, Structures, and Turbulence) code and experiments on the wind turbine simulator(WTS) based test bench are presented to verify the efficiency improvement of the proposed control strategy with less cost of drive-train load.展开更多
Recently,power electronic transformers(PETs)have received widespread attention owing to their flexible networking,diverse operating modes,and abundant control objects.In this study,we established a steady-state model ...Recently,power electronic transformers(PETs)have received widespread attention owing to their flexible networking,diverse operating modes,and abundant control objects.In this study,we established a steady-state model of PETs and applied it to the power flow calculation of AC-DC hybrid systems with PETs,considering the topology,power balance,loss,and control characteristics of multi-port PETs.To address new problems caused by the introduction of the PET port and control equations to the power flow calculation,this study proposes an iterative method of AC-DC mixed power flow decoupling based on step optimization,which can achieve AC-DC decoupling and effectively improve convergence.The results show that the proposed algorithm improves the iterative method and overcomes the overcorrection and initial value sensitivity problems of conventional iterative algorithms.展开更多
In southern China, power cable lines often running in water, and the state of XLPE insulation is difficult to detection effectively. This paper studied loss parameters online diagnosis technology of power cable insula...In southern China, power cable lines often running in water, and the state of XLPE insulation is difficult to detection effectively. This paper studied loss parameters online diagnosis technology of power cable insulation. An online loss parameters diagnosis device was development, which consists of current comparator, voltage controlled current source (VCCS), standard capacitor, GPRS wireless transmission system, control system and the data processing unit. 108 cables were detected using this device, and it was found out that one cable appeared to middle aging and eight cables appeared to slight aging. The butterfly water trees were observed in middle aging cable, which prove the effectiveness of online testing in the loss current measurement.展开更多
Attack surfaces, as one of the security models, can help people to analyse the security of systems in cyberspace, such as risk assessment by utilizing various security metrics or providing a cost-effective network har...Attack surfaces, as one of the security models, can help people to analyse the security of systems in cyberspace, such as risk assessment by utilizing various security metrics or providing a cost-effective network hardening solution. Numerous attack surface models have been proposed in the past decade,but they are not appropriate for describing complex systems with heterogeneous components. To address this limitation, we propose to use a two-layer Hierarchical Attack Surface Network(HASN) that models the data interactions and resource distribution of the system in a component-oriented view. First, we formally define the HASN by extending the entry point and exit point framework. Second, in order to assess data input risk and output risk on the HASN, we propose two behaviour models and two simulation-based risk metrics. Last, we conduct experiments for three network systems. Our experimental results show that the proposed approach is applicable and effective.展开更多
In order to evaluate the safe and stable operation of distribution network with the distributed photovoltaic (PV), the?security of distribution network is researched. On the basis of electricity supply security, volta...In order to evaluate the safe and stable operation of distribution network with the distributed photovoltaic (PV), the?security of distribution network is researched. On the basis of electricity supply security, voltage quality and network losses,?the index system of static security is established. The paper simulates the uncertainty and random characteristics of PV by OpenDSS. The typical scenes that PV accessed to the distribution network are designed.?The paper summarizes the results of voltage fluctuation and network losses and uses indices to quantify it under different scenes. Based on the index system, the paper proposes some recommendations on PV permeability, interconnected locations, dispersion degrees and power factors when the distributed PV accessed to the distribution network.展开更多
Accuracy measurement of the Non-soluble Deposit Density (NSDD) on the insulator surface is very important for the transmission line anti-pollution flashover works. A method to measure the NSDD on double sheds porcelai...Accuracy measurement of the Non-soluble Deposit Density (NSDD) on the insulator surface is very important for the transmission line anti-pollution flashover works. A method to measure the NSDD on double sheds porcelain insulator surface based on laser transmission principle is proposed in this paper. Laser unit and luminous intensity sensor are installed between the up and down surface of the double sheds porcelain insulators, two glass tablets are put between the double sheds. The contamination on the glass tablets will influence the luminous intensity that reaches the intensity sensor. The luminous signal is changed to electrical signal, and the insulator’s NSDD could be obtained based on the difference of luminous intensity. The device can be used in online monitoring of the insulator's NSDD condition on the insulator surface.展开更多
As the emergency power supply for a simulation substation,lead-acid batteries have a work pattern featuring noncontinuous operation,which leads to capacity regeneration.However,the accurate estimation of battery state...As the emergency power supply for a simulation substation,lead-acid batteries have a work pattern featuring noncontinuous operation,which leads to capacity regeneration.However,the accurate estimation of battery state of charge(SOC),a measurement of the amount of energy available in a battery,remains a hard nut to crack because of the non-stationarity and randomness of battery capacity change.This paper has proposed a comprehensive method for lead-acid battery SOC estimation,which may aid in maintaining a reasonable charging schedule in a simulation substation and improving battery’s durability.Based on the battery work pattern,an improved Ampere-hour method is used to calculate the SOC during constant current and constant voltage(CC/CV)charging and discharging.In addition,the combined Particle Swarm Optimization(PSO)and Least Squares Support Vector Machine(LSSVM)model is used to estimate the SOC during non-CC discharging.Experimental results show that this method is workable in online SOC estimation of working batteries in a simulation substaion,with the maximum relative error standing at only 2.1%during the non-training period,indicating a high precision and wide applicability.展开更多
The nanosecond single pulse was employed here to generate a large volume glow discharge between the wire-plane electrodes in air. In order to find requirements on pulse waveform for generation of a large volume discha...The nanosecond single pulse was employed here to generate a large volume glow discharge between the wire-plane electrodes in air. In order to find requirements on pulse waveform for generation of a large volume discharge at atmospheric pressure, the effect of pulse risetime, pulse width, and amplitude on glow discharge has been widely investigated in this paper. Results reveal that a large volume glow discharge can be generated in an inhomogeneous electric field under the single pulse with the faster risetime, the lower peak amplitude. The pulse width has almost no influence on the density of glow discharge, but which has a great influence on the transition from glow discharge to streamer discharge. A model of inter-shielding-effect has been proposed to explain the influence of waveform parameters on pulsed glow discharge.展开更多
The unified power flow controller(UPFC)based on modular multilevel converter(MMC) is the most creative flexible ac transmission system(FACTS) device. In theory, the output voltage of the series MMC in MMCUPFC can be r...The unified power flow controller(UPFC)based on modular multilevel converter(MMC) is the most creative flexible ac transmission system(FACTS) device. In theory, the output voltage of the series MMC in MMCUPFC can be regulated from 0 to the rated value. However,there would be relatively large harmonics in the output voltage if the voltage modulation ratio is small. In order to analyze the influence of MMC-UPFC on the harmonics of the power grid, the theoretical calculation method and spectra of the output voltage harmonics of MMC are presented. Subsequently, the calculation formulas of the harmonics in the power grid with UPFC are proposed. Based on it, the influence of UPFC on the grid voltage harmonics is evaluated, when MMC-UPFC is operated with different submodular numbers and voltage modular ratios. Eventually, the proposed analysis method is validated using digital simulation. The study results would provide guideline for the design and operation of MMC-UPFC project.展开更多
The increase of energy consumption has caused power systems to operate close to the limit of their capacity.The distributed power flow controller(DPFC),as a new member of distributed flexible AC transmission systems,i...The increase of energy consumption has caused power systems to operate close to the limit of their capacity.The distributed power flow controller(DPFC),as a new member of distributed flexible AC transmission systems,is introduced to remove this barrier.This paper proposes an optimal DPFC configuration method to enhance system loadability considering economic performance based on mixed integer linear programming.The conflicting behavior of system loadability and DPFC investment is analyzed and optimal solutions are calculated.Thereafter,the fuzzy decision-making method is implemented for determining the most preferred solution.In the most preferred solution obtained,the investment of DPFCs is minimized to find the optimal number,locations and set points.Simulation results on the IEEERTS79 system demonstrate that the proposed method is effective and reasonable.展开更多
Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this...Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics(PVs), batteries(BEs) and electric vehicles(EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources(DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation,so in the second stage, a power dispatch model is proposed the active distribution network(ADN) is an effective mea-as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.展开更多
The optimal configuration of battery energy storage system is key to the designing of a microgrid.In this paper,a optimal configuration method of energy storage in grid-connected microgrid is proposed.Firstly,the two-...The optimal configuration of battery energy storage system is key to the designing of a microgrid.In this paper,a optimal configuration method of energy storage in grid-connected microgrid is proposed.Firstly,the two-layer decision model to allocate the capacity of storage is established.The decision variables in outer programming model are the capacity and power of the storage system.The objective is the least investment on the battery energy storage system.The decision variable in inner programming model is the charging and discharging power of battery.The objective is the lowest power fluctuation on the connection line.Then a case containing a grid-connected microgrid with wind power,photovoltaic,battery energy storage and load is studied,and the multi-scenario probabilistic method is used.The last result of energy storage configuration is calculated through the probability of each scene.展开更多
Control strategy of unified power flow controller(UPFC)utilizing dq decoupling control is deduced in this paper,which can closely follow the control orders of the active and reactive power.The subsynchronous resonance...Control strategy of unified power flow controller(UPFC)utilizing dq decoupling control is deduced in this paper,which can closely follow the control orders of the active and reactive power.The subsynchronous resonance(SSR)characteristics of a series compensated system equipped with UPFC are studied,and the results reveal that SSR characteristics of the system may vary significantly with UPFC in service or not.Consequently,supplementary subsynchronous damping controller(SSDC)for UPFC is proposed and investigated,and the effectiveness of the proposed SSDC is verified by damping torque analysis and time domain simulations.展开更多
Coordinated charging of electric vehicles(EVs)is critical to provide safe and cost effective operation of distribution systems where household single phase charging of EV could contribute to imbalance of the distribut...Coordinated charging of electric vehicles(EVs)is critical to provide safe and cost effective operation of distribution systems where household single phase charging of EV could contribute to imbalance of the distribution system.To date,reported researches on optimization methods for coordinated charging aiming at minimizing power losses have the disadvantages of low calculation efficiency when applied to large systems or have not taken the voltage constraints into account.The phase component and polar coordinates power flow equations of an unbalanced distribution system are derived.Primal dual interior point dynamic programming is introduced for coordinated charging of EVs to minimize distribution system losses where charging demand,voltage and current constraints have been taken into account.The proposed optimization is evaluated using an actual 423-bus case as the test system.Results are promisingwith the proposed method having good convergence under time-efficient calculations while providing optimization of power losses,lower load variance,and improvement of voltage profile versus uncoordinated scenarios.展开更多
The operational stability and economy of multi-energy systems(MES)are threatened by various uncertainties,such as variable renewable energy power,energy demands,and weather conditions.Most of the existing methods for ...The operational stability and economy of multi-energy systems(MES)are threatened by various uncertainties,such as variable renewable energy power,energy demands,and weather conditions.Most of the existing methods for the dispatch decisions of MES are based on the prescribed probability distribution or uncertainty sets of random variables,which have many disadvantages,such as potential infeasibility and over-conservatism.In this paper,we propose a novel dispatch model for MES that integrates dispatch decision making,uncertainty set selection,and operational cost control into a unified framework.First,the deterministic dispatch model of MES is introduced,in which the physical characteristics of district heating systems and buildings are fully considered.Then,a novel decision framework that combines the two-stage dispatch strategy and info-gap decision theory(IGDT)is proposed for MES,where the uncertainty set is flexible and can be optimized based on the operational cost budget.Finally,a revised algorithm,based on the column-and-constraint generation method,is proposed for the model.Case studies are performed on MES that includes a 33-bus distribution system and a heating network modified from a real 51-node network located in Jinlin Province,China.The results verify the effectiveness of the proposed method.展开更多
This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-ori...This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.展开更多
基金supported partially by a MOE Tier 1 Thematic grant(23070749).
文摘In this paper,the explicit state-space model for a multi-inverter system including grid-following inverter-based generators(IBGs)and grid-forming IBGs is developed by the two-level component connection method(CCM),which modularized inverter control blocks at the primary level and IBGs at the secondary level.Based on the comprehensive state-space model representing full order of system dynamics,eigenvalues of the overall system are thoroughly analyzed,identifying potential adverse impacts of not only grid-following inverters,but also grid forming inverters on the system small-signal stability,with the underlying principle of oscillations also understood.Numerical and simulation results validate effectiveness of the proposed methodology on IEEE benchmarking 39-bus system.
基金supported by the National Natural Science Foundation of China(Grant 62103101)the Natural Science Foundation of Jiangsu Province of China(Grant BK20210217)+5 种基金the China Postdoctoral Science Foundation(Grant 2022M710680)the National Natural Science Foundation of China(Grant 62273094)the"Zhishan"Scholars Programs of Southeast Universitythe Fundamental Science(Natural Science)General Program of Jiangsu Higher Education Institutions(No.21KJB470020)the Open Research Fund of Jiangsu Collaborative Innovation Center for Smart Distribution Network,Nanjing Institute of Technology(No.XTCX202102)the Introduced Talents Scientific Research Start-up Fund Project,Nanjing Institute of Technology(No.YKJ202133).
文摘This paper presents a finite-time economic model predictive control(MPC)algorithm that can be used for frequency regulation and optimal load dispatch in multi-area power systems.Economic MPC can be used in a power system to ensure frequency stability,real-time economic optimization,control of the system and optimal load dispatch from it.A generalized terminal penalty term was used,and the finite-time convergence of the system was guaranteed.The effectiveness of the proposed model predictive control algorithm was verified by simulating a power system,which had two areas connected by an AC tie line.The simulation results demonstrated the effectiveness of the algorithm.
基金supported by the National Natural Science Foundation of China(61203129,61174038,61473151,51507080)the Fundamental Research Funds for the Central Universities(30915011104,30920130121010,30920140112005)
文摘Since mechanical loads exert a significant influence on the life span of wind turbines, the reduction of transient load on drive-train shaft has received more attention when implementing a maximum power point tracking(MPPT) controller.Moreover, a trade-off between the efficiency of wind energy extraction and the load level of drive-train shaft becomes a key issue. However, for the existing control strategies based on nonlinear model of wind turbines, the MPPT efficiencies are improved at the cost of the intensive fluctuation of generator torque and significant increase of transient load on drive train shaft. Hence, in this paper, a nonlinear controller with variable parameter is proposed for improving MPPT efficiency and mitigating transient load on drive-train simultaneously. Then,simulations on FAST(Fatigue, Aerodynamics, Structures, and Turbulence) code and experiments on the wind turbine simulator(WTS) based test bench are presented to verify the efficiency improvement of the proposed control strategy with less cost of drive-train load.
基金supported by the National Key Research and Development Program of China(2017YFB0903300).
文摘Recently,power electronic transformers(PETs)have received widespread attention owing to their flexible networking,diverse operating modes,and abundant control objects.In this study,we established a steady-state model of PETs and applied it to the power flow calculation of AC-DC hybrid systems with PETs,considering the topology,power balance,loss,and control characteristics of multi-port PETs.To address new problems caused by the introduction of the PET port and control equations to the power flow calculation,this study proposes an iterative method of AC-DC mixed power flow decoupling based on step optimization,which can achieve AC-DC decoupling and effectively improve convergence.The results show that the proposed algorithm improves the iterative method and overcomes the overcorrection and initial value sensitivity problems of conventional iterative algorithms.
文摘In southern China, power cable lines often running in water, and the state of XLPE insulation is difficult to detection effectively. This paper studied loss parameters online diagnosis technology of power cable insulation. An online loss parameters diagnosis device was development, which consists of current comparator, voltage controlled current source (VCCS), standard capacitor, GPRS wireless transmission system, control system and the data processing unit. 108 cables were detected using this device, and it was found out that one cable appeared to middle aging and eight cables appeared to slight aging. The butterfly water trees were observed in middle aging cable, which prove the effectiveness of online testing in the loss current measurement.
基金supported by the Jiangsu Provincial Natural Science Foundation of China(no.BK20150721)the 2017 National Key Research and Development Program of China(no.2017YFB0802900)
文摘Attack surfaces, as one of the security models, can help people to analyse the security of systems in cyberspace, such as risk assessment by utilizing various security metrics or providing a cost-effective network hardening solution. Numerous attack surface models have been proposed in the past decade,but they are not appropriate for describing complex systems with heterogeneous components. To address this limitation, we propose to use a two-layer Hierarchical Attack Surface Network(HASN) that models the data interactions and resource distribution of the system in a component-oriented view. First, we formally define the HASN by extending the entry point and exit point framework. Second, in order to assess data input risk and output risk on the HASN, we propose two behaviour models and two simulation-based risk metrics. Last, we conduct experiments for three network systems. Our experimental results show that the proposed approach is applicable and effective.
文摘In order to evaluate the safe and stable operation of distribution network with the distributed photovoltaic (PV), the?security of distribution network is researched. On the basis of electricity supply security, voltage quality and network losses,?the index system of static security is established. The paper simulates the uncertainty and random characteristics of PV by OpenDSS. The typical scenes that PV accessed to the distribution network are designed.?The paper summarizes the results of voltage fluctuation and network losses and uses indices to quantify it under different scenes. Based on the index system, the paper proposes some recommendations on PV permeability, interconnected locations, dispersion degrees and power factors when the distributed PV accessed to the distribution network.
文摘Accuracy measurement of the Non-soluble Deposit Density (NSDD) on the insulator surface is very important for the transmission line anti-pollution flashover works. A method to measure the NSDD on double sheds porcelain insulator surface based on laser transmission principle is proposed in this paper. Laser unit and luminous intensity sensor are installed between the up and down surface of the double sheds porcelain insulators, two glass tablets are put between the double sheds. The contamination on the glass tablets will influence the luminous intensity that reaches the intensity sensor. The luminous signal is changed to electrical signal, and the insulator’s NSDD could be obtained based on the difference of luminous intensity. The device can be used in online monitoring of the insulator's NSDD condition on the insulator surface.
基金The authors received funding for this study from Science and Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.(J2021020).
文摘As the emergency power supply for a simulation substation,lead-acid batteries have a work pattern featuring noncontinuous operation,which leads to capacity regeneration.However,the accurate estimation of battery state of charge(SOC),a measurement of the amount of energy available in a battery,remains a hard nut to crack because of the non-stationarity and randomness of battery capacity change.This paper has proposed a comprehensive method for lead-acid battery SOC estimation,which may aid in maintaining a reasonable charging schedule in a simulation substation and improving battery’s durability.Based on the battery work pattern,an improved Ampere-hour method is used to calculate the SOC during constant current and constant voltage(CC/CV)charging and discharging.In addition,the combined Particle Swarm Optimization(PSO)and Least Squares Support Vector Machine(LSSVM)model is used to estimate the SOC during non-CC discharging.Experimental results show that this method is workable in online SOC estimation of working batteries in a simulation substaion,with the maximum relative error standing at only 2.1%during the non-training period,indicating a high precision and wide applicability.
文摘The nanosecond single pulse was employed here to generate a large volume glow discharge between the wire-plane electrodes in air. In order to find requirements on pulse waveform for generation of a large volume discharge at atmospheric pressure, the effect of pulse risetime, pulse width, and amplitude on glow discharge has been widely investigated in this paper. Results reveal that a large volume glow discharge can be generated in an inhomogeneous electric field under the single pulse with the faster risetime, the lower peak amplitude. The pulse width has almost no influence on the density of glow discharge, but which has a great influence on the transition from glow discharge to streamer discharge. A model of inter-shielding-effect has been proposed to explain the influence of waveform parameters on pulsed glow discharge.
基金supported by State Grid Corporation of China(SGCC)’s Major Science and Technology Demonstrative Project of UPFC in West Nanjing Power Grid(No.SGCC-2015-011)
文摘The unified power flow controller(UPFC)based on modular multilevel converter(MMC) is the most creative flexible ac transmission system(FACTS) device. In theory, the output voltage of the series MMC in MMCUPFC can be regulated from 0 to the rated value. However,there would be relatively large harmonics in the output voltage if the voltage modulation ratio is small. In order to analyze the influence of MMC-UPFC on the harmonics of the power grid, the theoretical calculation method and spectra of the output voltage harmonics of MMC are presented. Subsequently, the calculation formulas of the harmonics in the power grid with UPFC are proposed. Based on it, the influence of UPFC on the grid voltage harmonics is evaluated, when MMC-UPFC is operated with different submodular numbers and voltage modular ratios. Eventually, the proposed analysis method is validated using digital simulation. The study results would provide guideline for the design and operation of MMC-UPFC project.
基金supported in part by the National Natural Science Foundation of China(No.51577030)in part by the project of State Grid Corporation of China(Research on flexible AC power flow control technology of transmission network based on a distributed power flow controller)(No.8516000700).
文摘The increase of energy consumption has caused power systems to operate close to the limit of their capacity.The distributed power flow controller(DPFC),as a new member of distributed flexible AC transmission systems,is introduced to remove this barrier.This paper proposes an optimal DPFC configuration method to enhance system loadability considering economic performance based on mixed integer linear programming.The conflicting behavior of system loadability and DPFC investment is analyzed and optimal solutions are calculated.Thereafter,the fuzzy decision-making method is implemented for determining the most preferred solution.In the most preferred solution obtained,the investment of DPFCs is minimized to find the optimal number,locations and set points.Simulation results on the IEEERTS79 system demonstrate that the proposed method is effective and reasonable.
基金supported in part by the National Science Foundation of China(No.51477029)the National Science and Technology Support Program of China(No.2015BAA01B01)the State Grid Corporation of China(No.SGTYHT/14-JS-188)
文摘Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics(PVs), batteries(BEs) and electric vehicles(EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources(DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation,so in the second stage, a power dispatch model is proposed the active distribution network(ADN) is an effective mea-as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.
基金The National Key Research and Development Plan(2017YFB0903504)Science and Technology Project of the SGCC(5210EF17001c).
文摘The optimal configuration of battery energy storage system is key to the designing of a microgrid.In this paper,a optimal configuration method of energy storage in grid-connected microgrid is proposed.Firstly,the two-layer decision model to allocate the capacity of storage is established.The decision variables in outer programming model are the capacity and power of the storage system.The objective is the least investment on the battery energy storage system.The decision variable in inner programming model is the charging and discharging power of battery.The objective is the lowest power fluctuation on the connection line.Then a case containing a grid-connected microgrid with wind power,photovoltaic,battery energy storage and load is studied,and the multi-scenario probabilistic method is used.The last result of energy storage configuration is calculated through the probability of each scene.
基金supported by National Natural Science Foundation of China (No.51607092)State Grid Corporation of China (SGCC)'s Major Science and Technology Demonstrative Project of UPFC in West Nanjing Power Grid (No.SGCC-2015-011)
文摘Control strategy of unified power flow controller(UPFC)utilizing dq decoupling control is deduced in this paper,which can closely follow the control orders of the active and reactive power.The subsynchronous resonance(SSR)characteristics of a series compensated system equipped with UPFC are studied,and the results reveal that SSR characteristics of the system may vary significantly with UPFC in service or not.Consequently,supplementary subsynchronous damping controller(SSDC)for UPFC is proposed and investigated,and the effectiveness of the proposed SSDC is verified by damping torque analysis and time domain simulations.
基金supported by the National Natural Science Fundation of China(No.51577046,No.5160070415)the National Defense Advanced Research Project(No.C1120110004,No.9140A27020211DZ5102)+1 种基金the Key Grant Project of Chinese Ministry of Education(No.313018)Anhui Provincial Science and Technology Foundation of China(No.1301022036)
文摘Coordinated charging of electric vehicles(EVs)is critical to provide safe and cost effective operation of distribution systems where household single phase charging of EV could contribute to imbalance of the distribution system.To date,reported researches on optimization methods for coordinated charging aiming at minimizing power losses have the disadvantages of low calculation efficiency when applied to large systems or have not taken the voltage constraints into account.The phase component and polar coordinates power flow equations of an unbalanced distribution system are derived.Primal dual interior point dynamic programming is introduced for coordinated charging of EVs to minimize distribution system losses where charging demand,voltage and current constraints have been taken into account.The proposed optimization is evaluated using an actual 423-bus case as the test system.Results are promisingwith the proposed method having good convergence under time-efficient calculations while providing optimization of power losses,lower load variance,and improvement of voltage profile versus uncoordinated scenarios.
基金the National Science Foundation of China(52207080)in part by the State Grid Jiangsu Electric Power Company Science and Technology Project(J2020001)in part by the National Science Foundation of Jiangsu Province(BK20200404).
文摘The operational stability and economy of multi-energy systems(MES)are threatened by various uncertainties,such as variable renewable energy power,energy demands,and weather conditions.Most of the existing methods for the dispatch decisions of MES are based on the prescribed probability distribution or uncertainty sets of random variables,which have many disadvantages,such as potential infeasibility and over-conservatism.In this paper,we propose a novel dispatch model for MES that integrates dispatch decision making,uncertainty set selection,and operational cost control into a unified framework.First,the deterministic dispatch model of MES is introduced,in which the physical characteristics of district heating systems and buildings are fully considered.Then,a novel decision framework that combines the two-stage dispatch strategy and info-gap decision theory(IGDT)is proposed for MES,where the uncertainty set is flexible and can be optimized based on the operational cost budget.Finally,a revised algorithm,based on the column-and-constraint generation method,is proposed for the model.Case studies are performed on MES that includes a 33-bus distribution system and a heating network modified from a real 51-node network located in Jinlin Province,China.The results verify the effectiveness of the proposed method.
基金supported in part by the Fundamental Research Funds for the Central Universities (No.2022SCU12005)the General Project of Natural Science Foundation of Sichuan Province (No.2022NSFSC0262)。
文摘This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.