To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy stora...To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy storage,incorporating daily minimum chargeable energy constraints,was developed.Firstly,considering the variations in the frequency of unit start-ups and shutdowns under different levels of net load fluctuation,a method was proposed to reduce decision time periods for unit start-up and shut-down operations.This approach,based on the characteristics of net load fluctuations,minimizes the decision variables of units,thereby simplifying the monthly schedulingmodel.Secondly,the relationship between energy storage charging and discharging power,net load,and the total maximum/minimum output of units was analyzed.Based on this,daily minimum chargeable energy constraints were established to ensure the energy storage system meets charging requirements under extreme net load scenarios.Finally,taking into account the operational costs of thermal generators and energy storage,load loss costs,and operational constraints,the reduced time-period monthly schedulingmodel was constructed.Case studies demonstrate that the proposedmethod effectively generates economical monthly operation plans for thermal generators and energy storage,significantly reduces model solution time,and satisfies the charging requirements of energy storage under extreme net load conditions.展开更多
The participation of wind farms in the former energymarket faces challenges such as power fluctuations and energy storage construction costs.To this end,this paper proposes a joint energy storage operation scheme for ...The participation of wind farms in the former energymarket faces challenges such as power fluctuations and energy storage construction costs.To this end,this paper proposes a joint energy storage operation scheme for multiple wind farms based on a leasingmodel,which assistswind farms in bidding for participation in the former energy market through leasing services,thereby enhancing energy storage efficiency and maximizing economic benefits.In this paper,based on theWeibull probability distribution to portray the uncertainty of wind power,and considering the lifetime capacity loss caused by charging and discharging of energy storage,we construct a bilateral transaction model aiming at maximizing the multi-objective revenue of wind farms and shared energy storage.The trading strategy is designed based on the Stackelberg game framework and solved jointly by the improved genetic algorithm and interior pointmethod.By exploring the effects of different lease price intervals on the overall systemperformance,and analyzing the systemstate undermultiple charging and discharging scenarios.The results show that a reasonable lease price range can significantly improve the energy storage system utilization and wind farmrevenue.Theprogramprovides new ideas to enhance the economic benefits of wind farms and promote the application of shared energy storage,and promotes the wide application of shared energy storage systems.展开更多
In response to the issue of determining the appropriate capacity when hybrid energy storage systems(HESS)collaborate with thermal power units(TPU)in the system’s secondary frequency regulation,a configuration method ...In response to the issue of determining the appropriate capacity when hybrid energy storage systems(HESS)collaborate with thermal power units(TPU)in the system’s secondary frequency regulation,a configuration method for HESS based on the analysis of frequency regulation demand analysis is proposed.And a corresponding simulation platform is developed.Firstly,a frequency modulation demand method for reducing the frequency modulation losses of TPU is proposed.Secondly,taking into comprehensive consideration that flywheel energy storage features rapid power response and battery energy storage has the characteristic of high energy density,a coordinated control strategy for HESS considering the self-recovery of state of charge(SOC)is put forward.Then,to measure the economic and technical performance of HESS in assisting the secondary frequency modulation of TPU,an optimized configurationmodel considering the full-life-cycle economy and frequency modulation performance of TPU and HESS system is constructed.Finally,a visual simulation platform for the combined frequency modulation of TPU and HESS is developed based on Matlab Appdesigner.Theresults of calculation examples indicate that the proposed configuration method can improve the overall economic efficiency and frequency modulation performance of TPU and HESS;The control strategy can not only prolong the service life of battery energy storage but also enhance the continuous response ability of HESS;The visual simulation platform is easy to use,and the simulation results are accurate and reliable.展开更多
Owing to their stability,doubly-fed induction generator(DFIG)integrated systems have gained considerable interest and are the most widely implemented type of wind turbines and due to the increasing escalation of the w...Owing to their stability,doubly-fed induction generator(DFIG)integrated systems have gained considerable interest and are the most widely implemented type of wind turbines and due to the increasing escalation of the wind generation penetration rate in power systems.In this study,we investigate a DFIG integrated system comprising four modules:(1)a wind turbine that considers the maximum power point tracking and pitch-angle control,(2)induction generator,(3)rotor/grid-side converter with the corresponding control strategy,and(4)AC power grid.The detailed small-signal modeling of the entire system is performed by linearizing the dynamic characteristic equation at the steady-state value.Furthermore,a dichotomy method is proposed based on the maximum eigenvalue real part function to obtain the critical value of the parameters.Root-locus analysis is employed to analyze the impact of changes in the phase-locked loop,short-circuit ratio,and blade inertia on the system stability.Lastly,the accuracy of the small-signal model and the real and imaginary parts of the calculated dominant poles in the theoretical analysis are verified using PSCAD/EMTDC.展开更多
Based on subsynchronous oscillation(SsO)caused by the connection of a direct drive wind farm to a weak alternating current(AC)grid,a complex torque model is proposed.By dividing the wind farm into a direct current cap...Based on subsynchronous oscillation(SsO)caused by the connection of a direct drive wind farm to a weak alternating current(AC)grid,a complex torque model is proposed.By dividing the wind farm into a direct current capacitor and electrical control part,the analytical expression of damping torque for the electrical control part is deduced and the mechanism of system subsynchronous oscillation is analyzed from the perspective of damping.The system stability is determined based on a damping coefficient less than O,and the influence laws of grid strength,operating conditions,and control parameters on system damping characteristics are analyzed,based on additional subsynchronous oscillation damping control(SSDC)to suppress SsO.Furthermore,the complex torque model of the parallel access system for multiple sub-wind farms is established,and the dynamic interaction between multiple sub-wind farms is preliminarily explored.The time-domain simulation model is built in EMTDC/PSCAD to verify the correctness of the theoretical analysis.展开更多
A time-varying optimization strategy for battery cluster power allocation is proposed to minimize energy loss in battery energy storage systems(BESS).First,the time-dependent loss characteristics of both storage and n...A time-varying optimization strategy for battery cluster power allocation is proposed to minimize energy loss in battery energy storage systems(BESS).First,the time-dependent loss characteristics of both storage and non-storage components in BESS are ana-lyzed.Based on this analysis,steady-state and transient methods for evaluating battery loss are proposed.Second,considering the distinct time-varying characteristics of various BESS components,the load-rate vs.equivalent-efficiency curve and the current-loss power component gradient field are introduced as analytical tools.These tools facilitate the derivation of optimization path for both time-varying and time-invariant energy compo-nents of BESS.Building on this foundation,a time-varying optimization strategy for battery cluster power allocation is developed,aiming to minimize energy loss while fully accounting for the dynamic characteristics of BESS.Compared to real-time optimization,this strategy prioritizes global optimality in the time domain,mitigates the risk of dimensionality curse,and enhances BESS efficiency.Finally,a Simulink/Simscape model is established based on real-world data to simulate internal component losses within BESS.The effectiveness of the proposed strategy is validated under a peak shaving scenario.Results indicate that,after optimization,the annual operational loss of BESS is reduced by 2.40%,while the energy round-trip efficiency is improved by 0.59%.展开更多
A small-signal model of photovoltaic(PV)generation connected to weak AC grid is established based on a detailed model of the structure and connection of a PV generation system. An eigenvalue analysis is then employed ...A small-signal model of photovoltaic(PV)generation connected to weak AC grid is established based on a detailed model of the structure and connection of a PV generation system. An eigenvalue analysis is then employed to study the stability of PV generation for different grid strengths and control parameters in a phaselocked loop(PLL) controller in the voltage source converter. The transfer function of the power control loop in the dq rotation frame is developed to reveal the influence mechanism of PLL gains on the small-signal stability of PV generation. The results can be summarized as follows:(1)oscillation phenomena at a frequency of about 5 Hz may occur when the grid strength is low;(2) the tuning control parameters of the PLL have a noticeable effect on the damping characteristics of the system, and larger proportional gain can improve the system damping;(3)within a frequency range of 4-5 Hz,the PLL controller has positive feedback on the power loop of PV generation. A virtual inductance control strategy is proposed to improve the operational stability of PV generation. Finally, a simulation model of PV generation connected to weak AC grid is built in PSCAD/EMTDC and the simulation results are used to validate the analysis.展开更多
Big wind farms must be integrated to power system.Wind power from big wind farms,with randomness,volatility and intermittent,will bring adverse impacts on the connected power system.High precision wind power forecasti...Big wind farms must be integrated to power system.Wind power from big wind farms,with randomness,volatility and intermittent,will bring adverse impacts on the connected power system.High precision wind power forecasting is helpful to reduce above adverse impacts.There are two kinds of wind power forecasting.One is to forecast wind power only based on its time series data.The other is to forecast wind power based on wind speeds from weather forecast.For a big wind farm,due to its spatial scale and dynamics of wind,wind speeds at different wind turbines are obviously different,that is called wind speed spatial dispersion.Spatial dispersion of wind speeds and its influence on the wind power forecasting errors have been studied in this paper.An error evaluation framework has been established to account for the errors caused by wind speed spatial dispersion.A case study of several wind farms has demonstrated that even ifthe forecasting average wind speed is accurate,the error caused by wind speed spatial dispersion cannot be ignored for the wind power forecasting of a wind farm.展开更多
The grid connection of a high proportion of re-newable energy generation increases the uncertainty in power systems.Therefore,the flexibility margin of different energy sources needs to be quantified to cope with the ...The grid connection of a high proportion of re-newable energy generation increases the uncertainty in power systems.Therefore,the flexibility margin of different energy sources needs to be quantified to cope with the uncertainty change and maintain the dynamic balance of power system flexibility.In this paper,first,the flexibility characteristics of source,net,load and power and load community(PLC)are analyzed.The dynamic equilibrium relationship among them is briefly introduced.Secondly,taking into full consideration the complex output characteristics of different energy sources and combining their respective flexibility characteristics,a quantitative model of the power source flexibility margin for thermal power,hydro-power,gas power and concentrating solar power is established.A quantitative model for a power source flexibility margin in PV and wind power based on blind number theory is estab-lished.Furthermore,the calculation method of theoretical power generation capacity,which can reflect different characteristics of output power of various energy sources,is presented.The actual output power of each power source in each period is predicted.Finally,a case study shows that the model and method can consider the operating characteristics of different types of power sources,and quickly and accurately quantify the adjustable range of flexibility margins of each power source at different periods of time,which can provide an important basis for evaluating the capacity of renewable energy consumption and the optimal operation of multi-energy power systems(MEPSs).展开更多
Integrating a battery energy storage system(ESS)with a large wind farm can smooth the intermittent power obtained from the wind farm,but the smoothing function will not be achieved if multiple ESSs are used to smooth ...Integrating a battery energy storage system(ESS)with a large wind farm can smooth the intermittent power obtained from the wind farm,but the smoothing function will not be achieved if multiple ESSs are used to smooth the fluctuations in individual wind power plants in a distributed pattern.Therefore,this study focuses on the development of a control strategy to optimize the use of multiple ESSs to accelerate the adoption of wind energy resources.This paper proposes a quasi-automated generation control(QAGC)strategy to coordinate multiple ESSs,which responds to the grid dispatch demand rather than smoothing out the intermittent power from individual wind farms.The aims of QAGC are to ensure that multiple ESSs provide a service that is as balanced as possible,so more wind power systems at various scales can be accepted by the grid,as well maximizing the low-carbon benefits of ESSs.The effectiveness of QAGC is demonstrated by using data from an actual gigawatt scale cluster of wind plants.展开更多
With the rapid development of wind power,the pressure on peak regulation of the power grid is increased.Electro-chemical energy storage is used on a large scale because of its high efficiency and good peak shaving and...With the rapid development of wind power,the pressure on peak regulation of the power grid is increased.Electro-chemical energy storage is used on a large scale because of its high efficiency and good peak shaving and valley fill-ing ability.The economic benefit evaluation of participating in power system auxiliary services has become the focus of attention since the development of grid-connected hundred megawatt-scale electrochemical energy storage systems(ESS).Based on the relationship between power and capacity in the process of peak shaving and valley filling,a dynamic economic benefit evaluation model of peak shaving assisted by hundred megawatt-scale electrochemi-cal ESS considering the equivalent life of the battery is proposed.The model considers the investment cost of energy storage,power efficiency,and operation and maintenance costs,and analyzes the dynamic economic benefits of dif-ferent energy storage technologies participating in the whole life cycle of the power grid.Then,according to the cur-rent ESS market environment,the auxiliary service compensation price,peak-valley price difference and energy stor-age cost unit price required to make the energy storage technology achieve the balance of payments are calculated,and the economic balance points of different energy storage types are clarified.Finally,based on the measured data of different provincial power grids,the economies of six energy storage types applied to three provincial power grids are compared and analyzed,and the rationality and effectiveness of the relevant models proposed are verified.The work has theoretical guiding significance for the economic benefit evaluation of hundred megawatt-scale electro-chemical energy storage.Highlights 1 A proportional relationship between grid filling power and capacity demand is proposed.It is used to determine the energy storage configuration for auxiliary peak shaving.2 A dynamic economic evaluation model considering energy storage investment and maintenance costs,electric-ity profit,and auxiliary service compensation is proposed.3 In the three provincial power grids,the economics of 6 hundred megawatt-scale electrochemical energy stor-ages are compared and analyzed.4 Auxiliary service compensation,time of day rate,and energy storage cost that enable energy storage to reach an economic equilibrium point are determined.展开更多
With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered th...With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered that the fault of DFIGs GTO is only related to the low/high voltage disturbances in the grid and manipulated as an electromagnetic transients.But,we discover that the fault of DFIGs GTO are also related to operating condition of DFIGs and schemes of crowbar protection equipped with DFIGs,and it may be extended to an electromechanical transient in some situations.Based on the investigation of the factors related to DFIGs GTO,such as degree of voltage disturbances,operating conditions of DFIGs and schemes of crowbar protection,three types of DFIGs GTOs are classified and corresponding mechanisms are revealed.The calculation methods to confirm the mechanism are established.The effectiveness of the proposed methods are verified by simulating some cases of DFISs GTO.展开更多
The cost of Energy Storage System(ESS)for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation.To solve this problem,the influence mechanism of actual...The cost of Energy Storage System(ESS)for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation.To solve this problem,the influence mechanism of actual operating conditions on the life degradation of Li-ion battery energy storage is analyzed.A control strategy of Li-ion ESS participating in grid frequency regulation is constructed and a cost accounting model for frequency regulation considering the effect of battery life degradation is established.The estimated operating life and annual average cost of the Li-ion ESS under different dead bands and SOC set-points are calculated.The case studies show that the estimated operating life of the Li-ion ESS under the actual operating condition differs significantly from the nominal life provided by the manufacturer under the standard condition and the full discharge mode.This paper provides an accurate costing method for the ESS participating in grid frequency regulation to help the promotion of the ESS to participate in the ancillary service market.展开更多
Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected...Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected by temperature,current,cycle number,discharge depth and other factors.This paper studies the modeling of lithium iron phosphate battery based on the Thevenin’s equivalent circuit and a method to identify the open circuit voltage,resistance and capacitance in the model is proposed.To improve the accuracy of the lithium battery model,a capacity estimation algorithm considering the capacity loss during the battery’s life cycle.In addition,this paper solves the SOC estimation issue of the lithium battery caused by the uncertain noise using the extended Kalman filtering(EKF)algorithm.A simulation model of actual lithium batteries is designed in Matlab/Simulink and the simulation results verify the accuracy of the model under different operating modes.展开更多
基金This study was supported by State Grid Corporation headquarters technology project(4000-202399368A-2-2-ZB).
文摘To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy storage,incorporating daily minimum chargeable energy constraints,was developed.Firstly,considering the variations in the frequency of unit start-ups and shutdowns under different levels of net load fluctuation,a method was proposed to reduce decision time periods for unit start-up and shut-down operations.This approach,based on the characteristics of net load fluctuations,minimizes the decision variables of units,thereby simplifying the monthly schedulingmodel.Secondly,the relationship between energy storage charging and discharging power,net load,and the total maximum/minimum output of units was analyzed.Based on this,daily minimum chargeable energy constraints were established to ensure the energy storage system meets charging requirements under extreme net load scenarios.Finally,taking into account the operational costs of thermal generators and energy storage,load loss costs,and operational constraints,the reduced time-period monthly schedulingmodel was constructed.Case studies demonstrate that the proposedmethod effectively generates economical monthly operation plans for thermal generators and energy storage,significantly reduces model solution time,and satisfies the charging requirements of energy storage under extreme net load conditions.
基金supported by the Technology Project of the State Grid Corporation Headquarters(Project No.4000-202399368A-2-2-ZB).
文摘The participation of wind farms in the former energymarket faces challenges such as power fluctuations and energy storage construction costs.To this end,this paper proposes a joint energy storage operation scheme for multiple wind farms based on a leasingmodel,which assistswind farms in bidding for participation in the former energy market through leasing services,thereby enhancing energy storage efficiency and maximizing economic benefits.In this paper,based on theWeibull probability distribution to portray the uncertainty of wind power,and considering the lifetime capacity loss caused by charging and discharging of energy storage,we construct a bilateral transaction model aiming at maximizing the multi-objective revenue of wind farms and shared energy storage.The trading strategy is designed based on the Stackelberg game framework and solved jointly by the improved genetic algorithm and interior pointmethod.By exploring the effects of different lease price intervals on the overall systemperformance,and analyzing the systemstate undermultiple charging and discharging scenarios.The results show that a reasonable lease price range can significantly improve the energy storage system utilization and wind farmrevenue.Theprogramprovides new ideas to enhance the economic benefits of wind farms and promote the application of shared energy storage,and promotes the wide application of shared energy storage systems.
基金supported by a Key Project of the National Natural Science Foundation of China under Grant 52337004.
文摘In response to the issue of determining the appropriate capacity when hybrid energy storage systems(HESS)collaborate with thermal power units(TPU)in the system’s secondary frequency regulation,a configuration method for HESS based on the analysis of frequency regulation demand analysis is proposed.And a corresponding simulation platform is developed.Firstly,a frequency modulation demand method for reducing the frequency modulation losses of TPU is proposed.Secondly,taking into comprehensive consideration that flywheel energy storage features rapid power response and battery energy storage has the characteristic of high energy density,a coordinated control strategy for HESS considering the self-recovery of state of charge(SOC)is put forward.Then,to measure the economic and technical performance of HESS in assisting the secondary frequency modulation of TPU,an optimized configurationmodel considering the full-life-cycle economy and frequency modulation performance of TPU and HESS system is constructed.Finally,a visual simulation platform for the combined frequency modulation of TPU and HESS is developed based on Matlab Appdesigner.Theresults of calculation examples indicate that the proposed configuration method can improve the overall economic efficiency and frequency modulation performance of TPU and HESS;The control strategy can not only prolong the service life of battery energy storage but also enhance the continuous response ability of HESS;The visual simulation platform is easy to use,and the simulation results are accurate and reliable.
基金supported by the Key Laboratory of Modern Power System Simulation and Control&Renewable Energy Technology,Ministry of Education(Northeast Electric Power University),Jilin 132012,China(MPSS2023-06).
文摘Owing to their stability,doubly-fed induction generator(DFIG)integrated systems have gained considerable interest and are the most widely implemented type of wind turbines and due to the increasing escalation of the wind generation penetration rate in power systems.In this study,we investigate a DFIG integrated system comprising four modules:(1)a wind turbine that considers the maximum power point tracking and pitch-angle control,(2)induction generator,(3)rotor/grid-side converter with the corresponding control strategy,and(4)AC power grid.The detailed small-signal modeling of the entire system is performed by linearizing the dynamic characteristic equation at the steady-state value.Furthermore,a dichotomy method is proposed based on the maximum eigenvalue real part function to obtain the critical value of the parameters.Root-locus analysis is employed to analyze the impact of changes in the phase-locked loop,short-circuit ratio,and blade inertia on the system stability.Lastly,the accuracy of the small-signal model and the real and imaginary parts of the calculated dominant poles in the theoretical analysis are verified using PSCAD/EMTDC.
基金supported by Integrated project of National Natural Science Foundation of China(No.U1866601)Science and Technology Project of State Grid Corporation of China(5230DK20004V)。
文摘Based on subsynchronous oscillation(SsO)caused by the connection of a direct drive wind farm to a weak alternating current(AC)grid,a complex torque model is proposed.By dividing the wind farm into a direct current capacitor and electrical control part,the analytical expression of damping torque for the electrical control part is deduced and the mechanism of system subsynchronous oscillation is analyzed from the perspective of damping.The system stability is determined based on a damping coefficient less than O,and the influence laws of grid strength,operating conditions,and control parameters on system damping characteristics are analyzed,based on additional subsynchronous oscillation damping control(SSDC)to suppress SsO.Furthermore,the complex torque model of the parallel access system for multiple sub-wind farms is established,and the dynamic interaction between multiple sub-wind farms is preliminarily explored.The time-domain simulation model is built in EMTDC/PSCAD to verify the correctness of the theoretical analysis.
基金supported by Key Program of the Na-tional Natural Science Foundation of China(No.52337004).
文摘A time-varying optimization strategy for battery cluster power allocation is proposed to minimize energy loss in battery energy storage systems(BESS).First,the time-dependent loss characteristics of both storage and non-storage components in BESS are ana-lyzed.Based on this analysis,steady-state and transient methods for evaluating battery loss are proposed.Second,considering the distinct time-varying characteristics of various BESS components,the load-rate vs.equivalent-efficiency curve and the current-loss power component gradient field are introduced as analytical tools.These tools facilitate the derivation of optimization path for both time-varying and time-invariant energy compo-nents of BESS.Building on this foundation,a time-varying optimization strategy for battery cluster power allocation is developed,aiming to minimize energy loss while fully accounting for the dynamic characteristics of BESS.Compared to real-time optimization,this strategy prioritizes global optimality in the time domain,mitigates the risk of dimensionality curse,and enhances BESS efficiency.Finally,a Simulink/Simscape model is established based on real-world data to simulate internal component losses within BESS.The effectiveness of the proposed strategy is validated under a peak shaving scenario.Results indicate that,after optimization,the annual operational loss of BESS is reduced by 2.40%,while the energy round-trip efficiency is improved by 0.59%.
基金supported by State Grid Corporation of China ‘‘Study on active frequency and voltage control technologies for second level power disturbance in photovoltaic power plant’’National Natural Science Foundation of China (No. 51277024)
文摘A small-signal model of photovoltaic(PV)generation connected to weak AC grid is established based on a detailed model of the structure and connection of a PV generation system. An eigenvalue analysis is then employed to study the stability of PV generation for different grid strengths and control parameters in a phaselocked loop(PLL) controller in the voltage source converter. The transfer function of the power control loop in the dq rotation frame is developed to reveal the influence mechanism of PLL gains on the small-signal stability of PV generation. The results can be summarized as follows:(1)oscillation phenomena at a frequency of about 5 Hz may occur when the grid strength is low;(2) the tuning control parameters of the PLL have a noticeable effect on the damping characteristics of the system, and larger proportional gain can improve the system damping;(3)within a frequency range of 4-5 Hz,the PLL controller has positive feedback on the power loop of PV generation. A virtual inductance control strategy is proposed to improve the operational stability of PV generation. Finally, a simulation model of PV generation connected to weak AC grid is built in PSCAD/EMTDC and the simulation results are used to validate the analysis.
基金funded by National Basic Research Program of China(973 Program)(No.2013CB228201)National Natural Science Foundation of China(No.51307017)
文摘Big wind farms must be integrated to power system.Wind power from big wind farms,with randomness,volatility and intermittent,will bring adverse impacts on the connected power system.High precision wind power forecasting is helpful to reduce above adverse impacts.There are two kinds of wind power forecasting.One is to forecast wind power only based on its time series data.The other is to forecast wind power based on wind speeds from weather forecast.For a big wind farm,due to its spatial scale and dynamics of wind,wind speeds at different wind turbines are obviously different,that is called wind speed spatial dispersion.Spatial dispersion of wind speeds and its influence on the wind power forecasting errors have been studied in this paper.An error evaluation framework has been established to account for the errors caused by wind speed spatial dispersion.A case study of several wind farms has demonstrated that even ifthe forecasting average wind speed is accurate,the error caused by wind speed spatial dispersion cannot be ignored for the wind power forecasting of a wind farm.
基金the National Key Research and Development Program of China(2017YFB0902200)Science and Technology Project of State Grid Corporation of China(5228001700CW)。
文摘The grid connection of a high proportion of re-newable energy generation increases the uncertainty in power systems.Therefore,the flexibility margin of different energy sources needs to be quantified to cope with the uncertainty change and maintain the dynamic balance of power system flexibility.In this paper,first,the flexibility characteristics of source,net,load and power and load community(PLC)are analyzed.The dynamic equilibrium relationship among them is briefly introduced.Secondly,taking into full consideration the complex output characteristics of different energy sources and combining their respective flexibility characteristics,a quantitative model of the power source flexibility margin for thermal power,hydro-power,gas power and concentrating solar power is established.A quantitative model for a power source flexibility margin in PV and wind power based on blind number theory is estab-lished.Furthermore,the calculation method of theoretical power generation capacity,which can reflect different characteristics of output power of various energy sources,is presented.The actual output power of each power source in each period is predicted.Finally,a case study shows that the model and method can consider the operating characteristics of different types of power sources,and quickly and accurately quantify the adjustable range of flexibility margins of each power source at different periods of time,which can provide an important basis for evaluating the capacity of renewable energy consumption and the optimal operation of multi-energy power systems(MEPSs).
基金This work is supported by National Basic Research Program of China(973 Program)(No.2013CB228201).
文摘Integrating a battery energy storage system(ESS)with a large wind farm can smooth the intermittent power obtained from the wind farm,but the smoothing function will not be achieved if multiple ESSs are used to smooth the fluctuations in individual wind power plants in a distributed pattern.Therefore,this study focuses on the development of a control strategy to optimize the use of multiple ESSs to accelerate the adoption of wind energy resources.This paper proposes a quasi-automated generation control(QAGC)strategy to coordinate multiple ESSs,which responds to the grid dispatch demand rather than smoothing out the intermittent power from individual wind farms.The aims of QAGC are to ensure that multiple ESSs provide a service that is as balanced as possible,so more wind power systems at various scales can be accepted by the grid,as well maximizing the low-carbon benefits of ESSs.The effectiveness of QAGC is demonstrated by using data from an actual gigawatt scale cluster of wind plants.
基金supported by Joint Foundation of Natural Science Foundation of Jilin Province(No.YDZJ202101ZYTS152).
文摘With the rapid development of wind power,the pressure on peak regulation of the power grid is increased.Electro-chemical energy storage is used on a large scale because of its high efficiency and good peak shaving and valley fill-ing ability.The economic benefit evaluation of participating in power system auxiliary services has become the focus of attention since the development of grid-connected hundred megawatt-scale electrochemical energy storage systems(ESS).Based on the relationship between power and capacity in the process of peak shaving and valley filling,a dynamic economic benefit evaluation model of peak shaving assisted by hundred megawatt-scale electrochemi-cal ESS considering the equivalent life of the battery is proposed.The model considers the investment cost of energy storage,power efficiency,and operation and maintenance costs,and analyzes the dynamic economic benefits of dif-ferent energy storage technologies participating in the whole life cycle of the power grid.Then,according to the cur-rent ESS market environment,the auxiliary service compensation price,peak-valley price difference and energy stor-age cost unit price required to make the energy storage technology achieve the balance of payments are calculated,and the economic balance points of different energy storage types are clarified.Finally,based on the measured data of different provincial power grids,the economies of six energy storage types applied to three provincial power grids are compared and analyzed,and the rationality and effectiveness of the relevant models proposed are verified.The work has theoretical guiding significance for the economic benefit evaluation of hundred megawatt-scale electro-chemical energy storage.Highlights 1 A proportional relationship between grid filling power and capacity demand is proposed.It is used to determine the energy storage configuration for auxiliary peak shaving.2 A dynamic economic evaluation model considering energy storage investment and maintenance costs,electric-ity profit,and auxiliary service compensation is proposed.3 In the three provincial power grids,the economics of 6 hundred megawatt-scale electrochemical energy stor-ages are compared and analyzed.4 Auxiliary service compensation,time of day rate,and energy storage cost that enable energy storage to reach an economic equilibrium point are determined.
基金supported in part by the National Basic Research Program of China(2013CB228201)。
文摘With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered that the fault of DFIGs GTO is only related to the low/high voltage disturbances in the grid and manipulated as an electromagnetic transients.But,we discover that the fault of DFIGs GTO are also related to operating condition of DFIGs and schemes of crowbar protection equipped with DFIGs,and it may be extended to an electromechanical transient in some situations.Based on the investigation of the factors related to DFIGs GTO,such as degree of voltage disturbances,operating conditions of DFIGs and schemes of crowbar protection,three types of DFIGs GTOs are classified and corresponding mechanisms are revealed.The calculation methods to confirm the mechanism are established.The effectiveness of the proposed methods are verified by simulating some cases of DFISs GTO.
基金This work is supported in part by Industrial Innovation of Jilin Province Development and Reform Commission(2017C017-2)Science&Technology Project of SGCC(Key technology and application of super large capac-ity battery energy storage system),and Jilin Provincial“13th Five-Year Plan”Science and Technology Project([2016]88).
文摘The cost of Energy Storage System(ESS)for frequency regulation is difficult to calculate due to battery’s degradation when an ESS is in grid-connected operation.To solve this problem,the influence mechanism of actual operating conditions on the life degradation of Li-ion battery energy storage is analyzed.A control strategy of Li-ion ESS participating in grid frequency regulation is constructed and a cost accounting model for frequency regulation considering the effect of battery life degradation is established.The estimated operating life and annual average cost of the Li-ion ESS under different dead bands and SOC set-points are calculated.The case studies show that the estimated operating life of the Li-ion ESS under the actual operating condition differs significantly from the nominal life provided by the manufacturer under the standard condition and the full discharge mode.This paper provides an accurate costing method for the ESS participating in grid frequency regulation to help the promotion of the ESS to participate in the ancillary service market.
基金This work is supported in part by Open Fund of State Key Laboratory of Operation and Control of Renewable Energy&Storage Systems(DGB51201700424)Industrial Innovation of Jilin Province Development and Reform Commission(2017C017-2)Jilin Provincial“13th Five-Year Plan”Science and Technology Project([2016]88).
文摘Modeling and state of charge(SOC)estimation of Lithium cells are crucial techniques of the lithium battery management system.The modeling is extremely complicated as the operating status of lithium battery is affected by temperature,current,cycle number,discharge depth and other factors.This paper studies the modeling of lithium iron phosphate battery based on the Thevenin’s equivalent circuit and a method to identify the open circuit voltage,resistance and capacitance in the model is proposed.To improve the accuracy of the lithium battery model,a capacity estimation algorithm considering the capacity loss during the battery’s life cycle.In addition,this paper solves the SOC estimation issue of the lithium battery caused by the uncertain noise using the extended Kalman filtering(EKF)algorithm.A simulation model of actual lithium batteries is designed in Matlab/Simulink and the simulation results verify the accuracy of the model under different operating modes.
