The data-driven approaches have been extensively developed for multi-operation impedance modeling of the renewable power generation equipment(RPGE).However,due to the black box of RPGE,the dataset used for establishin...The data-driven approaches have been extensively developed for multi-operation impedance modeling of the renewable power generation equipment(RPGE).However,due to the black box of RPGE,the dataset used for establishing impedance model lacks theoretical guidance for data generation,which reduces data quality and results in a large amount of data redundancy.To address this issue,this paper proposes an impedance dataset optimization method for data-driven modeling of RPGE considering multi-operation conditions.The objective is to improve the data quality of the impedance dataset,thereby reflecting the overall impedance characteristics with a reduced data amount.Firstly,the impact of operation conditions on impedance is evaluated to optimize the selection of operating points.Secondly,at each operating point,the frequency distribution is designed to reveal the impedance characteristics with fewer measurement points.Finally,a serial update method for measured datasets and the multi-operation impedance model is developed to further refine the dataset.The experiments based on control-hardware-in-loop(CHIL)are conducted to verify the effectiveness of the proposed method.展开更多
On March 19, the construction of a 10-MW photovoltaic power plant and a 1 000-kW new type geothermal power generation project were started by Guodian Longyuan Group in Yanbajing Town, Dangxiong County of Tibet.
Equivalent models are essential for time-domain simulation and harmonic stability evaluation of renewable power plants.Such harmonic instability may co-occur at the plant-level and unit-level,or it may only occur at t...Equivalent models are essential for time-domain simulation and harmonic stability evaluation of renewable power plants.Such harmonic instability may co-occur at the plant-level and unit-level,or it may only occur at the unit-level,manifesting as local resonances.However,conventional equivalent methods can only simulate plant-level instability,but cannot consider such unit-level instability.To address this problem,the main contributions of this paper are as follows:1)Based on the impedance matrix and the eigenvalue analysis,the reason why conventional equivalent methods cannot accurately simulate unitlevel stability is studied.2)A double-machine equivalent method is proposed.The model used in this method is a minimumscale equivalent model capable of simulating plant-level and unit-level stability,simultaneously.It uses two single-machine models to represent a generation cluster containing N generation units.A single-machine model M_(1) represents N—1 generation units for simplification,while another single-machine model M_(2) represents the remaining one generation unit for simulating unitlevel stability.3)Furthermore,a practical improvement approach of the double-machine equivalent method is proposed for taking into account operating point differences and complex connection conditions.Finally,the proposed method is verified by simulations and experiments.展开更多
The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates signi...The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.展开更多
The advancements in distributed generation(DG)technologies such as solar panels have led to a widespread integration of renewable power generation in modern power systems.However,the intermittent nature of renewable e...The advancements in distributed generation(DG)technologies such as solar panels have led to a widespread integration of renewable power generation in modern power systems.However,the intermittent nature of renewable energy poses new challenges to the network operational planning with underlying uncertainties.This paper proposes a novel probabilistic scheme for renewable solar power generation forecasting by addressing data and model parameter uncertainties using Bayesian bidirectional long short-term memory(BiLSTM)neural networks,while handling the high dimensionality in weight parameters using variational auto-encoders(VAE).The forecasting performance of the proposed method is evaluated using various deterministic and probabilistic evaluation metrics such as root-mean square error(RMSE),Pinball loss,etc.Furthermore,reconstruction error and computational time are also monitored to evaluate the dimensionality reduction using the VAE component.When compared with benchmark methods,the proposed method leads to significant improvements in weight reduction,i.e.,from 76,4224 to 2,022 number of weight parameters,quantifying to 97.35%improvement in weight parameters reduction and 37.93%improvement in computational time for 6 months of solar power generation data.展开更多
This paper investigates long-term energy strategy compatible with significant reduction of world carbon dioxide （CO2） emissions, employing a long-term global energy model, Dynamic New Earth 21 （called DNE21）. The ...This paper investigates long-term energy strategy compatible with significant reduction of world carbon dioxide （CO2） emissions, employing a long-term global energy model, Dynamic New Earth 21 （called DNE21）. The model seeks the optimal energy mix from 2000 to 2100 that minimizes the world total energy system cost under various kinds of energy and technological constraints, such as energy resource constraints, energy supply and demand balance constraints, and CO2 emissions constraints. This paper discusses the results of primary energy supply, power generation mix, CO2 emission, CCS （carbon capture and storage） and total system costs for six regions including world as a whole. To evaluate viable pathways forward for implementation of sustainable energy strategies, nuclear power generation is a viable source of clean and green energy to mitigate the CO2 emissions. Present research shows simulation results in two cases consisting of no CO2 regulation case （base case） and CO2 REG case （regulation case） which halves the world CO2 emissions by the year 2050. Main findings of this research describe that renewable and nuclear power generation will contribute significantly to mitigate the CO2 emission worldwide.展开更多
To tackle emerging power system small-signal stability problems such as wideband oscillations induced by the large-scale integration of renewable energy and power electronics,it is crucial to review and compare existi...To tackle emerging power system small-signal stability problems such as wideband oscillations induced by the large-scale integration of renewable energy and power electronics,it is crucial to review and compare existing small-signal stability analysis methods.On this basis,guidance can be provided on determining suitable analysis methods to solve relevant small-signal stability problems in power electronics-dominated power systems(PEDPSs).Various mature methods have been developed to analyze the small-signal stability of PEDPSs,including eigenvalue-based methods,Routh stability criterion,Nyquist/Bode plot based methods,passivity-based methods,positive-net-damping method,lumped impedance-based methods,bifurcation-based methods,etc.In this paper,the application conditions,advantages,and limitations of these criteria in identifying oscillation frequencies and stability margins are reviewed and compared to reveal and explain connections and discrepancies among them.Especially,efforts are devoted to mathematically proving the equivalence between these small-signal stability criteria.Finally,the performance of these criteria is demonstrated and compared in a 4-machine 2-area power system with a wind farm and an IEEE 39-bus power system with 3 wind farms.展开更多
The analysis of the wind-driven self-excited induction generators （SEIGs） connected to the grid through power converters has been developed in this paper. For this analysis, a method of representing the grid power a...The analysis of the wind-driven self-excited induction generators （SEIGs） connected to the grid through power converters has been developed in this paper. For this analysis, a method of representing the grid power as equivalent load resistance in the steady-state equivalent circuit of SEIG has been formulated. The technique of genetic algorithm （GA） has been adopted for making the analysis of the proposed system simple and straightfor- ward. The control of SEIG is attempted by connecting an uncontrolled diode bridge rectifier （DBR） and a line commutated inverter （LCI） between the generator term- inals and three-phase utility grid. A simple control technique for maximum power point tracking （MPPT） in wind energy conversion systems （WECS）, in which the firing angle of the LCI alone needs to be controlled by sensing the rotor speed of the generator has been proposed. The effectiveness of the proposed method of MPPT and method of analysis of this wind-driven SEIG-converter system connected to the grid through power converters has been demonstrated by experiments and simulation. These experimental and simulated results confirm the usefulness and successful working of the proposed system and its analysis.展开更多
With the global energy transition,the proportion of renewable energy power generation in total electricity production has exceeded 30%and continues to rise,even the ratio is higher in China.Multi-terminal high-voltage...With the global energy transition,the proportion of renewable energy power generation in total electricity production has exceeded 30%and continues to rise,even the ratio is higher in China.Multi-terminal high-voltage direct-current(MT-HVDC)transmission systems have advantages of integration of distributed renewable energy sources,dynamic grid interconnections,and reliable islanding operation capabilities,being critical for next-generation power grid.Current limiting technologies are pivotal in maintaining grid safety and stability,especially for HVDC systems without natural zero-crossing point in fault currents.In this perspective,a superconducting fault current limiter(SFCL)with combination of resistance and inductance is necessary and more effective solution in protecting MT-HVDC transmission systems.展开更多
Uncertainty in distributed renewable generation threatens the security of power distribution systems.The concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable gene...Uncertainty in distributed renewable generation threatens the security of power distribution systems.The concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating point.Although DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution networks.To achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex relaxation.Secondorder cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve tractability.Further,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable region.Case studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.展开更多
基金supported by the National Natural Science Foundation of China(No.52325702)。
文摘The data-driven approaches have been extensively developed for multi-operation impedance modeling of the renewable power generation equipment(RPGE).However,due to the black box of RPGE,the dataset used for establishing impedance model lacks theoretical guidance for data generation,which reduces data quality and results in a large amount of data redundancy.To address this issue,this paper proposes an impedance dataset optimization method for data-driven modeling of RPGE considering multi-operation conditions.The objective is to improve the data quality of the impedance dataset,thereby reflecting the overall impedance characteristics with a reduced data amount.Firstly,the impact of operation conditions on impedance is evaluated to optimize the selection of operating points.Secondly,at each operating point,the frequency distribution is designed to reveal the impedance characteristics with fewer measurement points.Finally,a serial update method for measured datasets and the multi-operation impedance model is developed to further refine the dataset.The experiments based on control-hardware-in-loop(CHIL)are conducted to verify the effectiveness of the proposed method.
文摘On March 19, the construction of a 10-MW photovoltaic power plant and a 1 000-kW new type geothermal power generation project were started by Guodian Longyuan Group in Yanbajing Town, Dangxiong County of Tibet.
基金supported by the Joint Funds of the National Natural Science Foundation of China(U23A20655)the Science and Technology Tackling Plan Project of Anhui Province(202423h08050008)the Science and Technology Project of State Grid Anhui Electric Power Co.,Ltd.(SGAHDK00CNJS2500397).
文摘Equivalent models are essential for time-domain simulation and harmonic stability evaluation of renewable power plants.Such harmonic instability may co-occur at the plant-level and unit-level,or it may only occur at the unit-level,manifesting as local resonances.However,conventional equivalent methods can only simulate plant-level instability,but cannot consider such unit-level instability.To address this problem,the main contributions of this paper are as follows:1)Based on the impedance matrix and the eigenvalue analysis,the reason why conventional equivalent methods cannot accurately simulate unitlevel stability is studied.2)A double-machine equivalent method is proposed.The model used in this method is a minimumscale equivalent model capable of simulating plant-level and unit-level stability,simultaneously.It uses two single-machine models to represent a generation cluster containing N generation units.A single-machine model M_(1) represents N—1 generation units for simplification,while another single-machine model M_(2) represents the remaining one generation unit for simulating unitlevel stability.3)Furthermore,a practical improvement approach of the double-machine equivalent method is proposed for taking into account operating point differences and complex connection conditions.Finally,the proposed method is verified by simulations and experiments.
基金supported by the National Natural Science Foundation of China under Grant 52407069the Science and Technology Project of Zhejiang Province under Grant 2024C01254the China Postdoctoral Science Foundation under Grant 2024T170766 and 2024M762824。
文摘The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.
文摘The advancements in distributed generation(DG)technologies such as solar panels have led to a widespread integration of renewable power generation in modern power systems.However,the intermittent nature of renewable energy poses new challenges to the network operational planning with underlying uncertainties.This paper proposes a novel probabilistic scheme for renewable solar power generation forecasting by addressing data and model parameter uncertainties using Bayesian bidirectional long short-term memory(BiLSTM)neural networks,while handling the high dimensionality in weight parameters using variational auto-encoders(VAE).The forecasting performance of the proposed method is evaluated using various deterministic and probabilistic evaluation metrics such as root-mean square error(RMSE),Pinball loss,etc.Furthermore,reconstruction error and computational time are also monitored to evaluate the dimensionality reduction using the VAE component.When compared with benchmark methods,the proposed method leads to significant improvements in weight reduction,i.e.,from 76,4224 to 2,022 number of weight parameters,quantifying to 97.35%improvement in weight parameters reduction and 37.93%improvement in computational time for 6 months of solar power generation data.
文摘This paper investigates long-term energy strategy compatible with significant reduction of world carbon dioxide （CO2） emissions, employing a long-term global energy model, Dynamic New Earth 21 （called DNE21）. The model seeks the optimal energy mix from 2000 to 2100 that minimizes the world total energy system cost under various kinds of energy and technological constraints, such as energy resource constraints, energy supply and demand balance constraints, and CO2 emissions constraints. This paper discusses the results of primary energy supply, power generation mix, CO2 emission, CCS （carbon capture and storage） and total system costs for six regions including world as a whole. To evaluate viable pathways forward for implementation of sustainable energy strategies, nuclear power generation is a viable source of clean and green energy to mitigate the CO2 emissions. Present research shows simulation results in two cases consisting of no CO2 regulation case （base case） and CO2 REG case （regulation case） which halves the world CO2 emissions by the year 2050. Main findings of this research describe that renewable and nuclear power generation will contribute significantly to mitigate the CO2 emission worldwide.
基金supported in part by the National Natural Science Foundation of China for the Research Project(No.52077188)in part by the Hong Kong Research Grant Council for the Research Project(No.15219619).
文摘To tackle emerging power system small-signal stability problems such as wideband oscillations induced by the large-scale integration of renewable energy and power electronics,it is crucial to review and compare existing small-signal stability analysis methods.On this basis,guidance can be provided on determining suitable analysis methods to solve relevant small-signal stability problems in power electronics-dominated power systems(PEDPSs).Various mature methods have been developed to analyze the small-signal stability of PEDPSs,including eigenvalue-based methods,Routh stability criterion,Nyquist/Bode plot based methods,passivity-based methods,positive-net-damping method,lumped impedance-based methods,bifurcation-based methods,etc.In this paper,the application conditions,advantages,and limitations of these criteria in identifying oscillation frequencies and stability margins are reviewed and compared to reveal and explain connections and discrepancies among them.Especially,efforts are devoted to mathematically proving the equivalence between these small-signal stability criteria.Finally,the performance of these criteria is demonstrated and compared in a 4-machine 2-area power system with a wind farm and an IEEE 39-bus power system with 3 wind farms.
文摘The analysis of the wind-driven self-excited induction generators （SEIGs） connected to the grid through power converters has been developed in this paper. For this analysis, a method of representing the grid power as equivalent load resistance in the steady-state equivalent circuit of SEIG has been formulated. The technique of genetic algorithm （GA） has been adopted for making the analysis of the proposed system simple and straightfor- ward. The control of SEIG is attempted by connecting an uncontrolled diode bridge rectifier （DBR） and a line commutated inverter （LCI） between the generator term- inals and three-phase utility grid. A simple control technique for maximum power point tracking （MPPT） in wind energy conversion systems （WECS）, in which the firing angle of the LCI alone needs to be controlled by sensing the rotor speed of the generator has been proposed. The effectiveness of the proposed method of MPPT and method of analysis of this wind-driven SEIG-converter system connected to the grid through power converters has been demonstrated by experiments and simulation. These experimental and simulated results confirm the usefulness and successful working of the proposed system and its analysis.
文摘With the global energy transition,the proportion of renewable energy power generation in total electricity production has exceeded 30%and continues to rise,even the ratio is higher in China.Multi-terminal high-voltage direct-current(MT-HVDC)transmission systems have advantages of integration of distributed renewable energy sources,dynamic grid interconnections,and reliable islanding operation capabilities,being critical for next-generation power grid.Current limiting technologies are pivotal in maintaining grid safety and stability,especially for HVDC systems without natural zero-crossing point in fault currents.In this perspective,a superconducting fault current limiter(SFCL)with combination of resistance and inductance is necessary and more effective solution in protecting MT-HVDC transmission systems.
基金the National Natural Science Foundation of China(Grant No.52177086)the Fundamental Research Funds for the Central Universities(Grant No.2023ZYGXZR063)。
文摘Uncertainty in distributed renewable generation threatens the security of power distribution systems.The concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating point.Although DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution networks.To achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex relaxation.Secondorder cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve tractability.Further,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable region.Case studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.
