The effect of energy on the natural environment has become increasingly severe as human consumption of fossil energy has increased.The capacity of the synchronous generators to keep working without losing synchronizat...The effect of energy on the natural environment has become increasingly severe as human consumption of fossil energy has increased.The capacity of the synchronous generators to keep working without losing synchronization when the system is exposed to severe faults such as short circuits is referred to as the power system’s transient stability.As the power system’s safe and stable operation and mechanism of action become more complicated,higher demands for accurate and rapid power system transient stability analysis are made.Current methods for analyzing transient stability are less accurate because they do not account formisclassification of unstable samples.As a result,this paper proposes a novel approach for analyzing transient stability.The key concept is to use deep forest(DF)and a neighborhood rough reduction approach together.Using the neighborhood rough sets,the original feature space is obtained by creating many optimal feature subsets at various granularity levels.Then,by deploying the DF cascade structure,the mapping connection between the transient stability state and the features is reinforced.The weighted voting technique is used in the learning process to increase the classification accuracy of unstable samples.When contrasted to current methods,simulation results indicate that the proposed approach outperforms them.展开更多
This paper presents a quantitative assessment of the transient stability of grid-forming converters,considering current limitations,inertia,and damping effects.The contributions are summarized in two main aspects:Firs...This paper presents a quantitative assessment of the transient stability of grid-forming converters,considering current limitations,inertia,and damping effects.The contributions are summarized in two main aspects:First,the analysis delves into transient stability under a general voltage sag scenario for a converter subject to current limitations.When the voltage sag exceeds a critical threshold,transient instability arises,with its severity influenced by the inertia and damping coefficients within the swing equation.Second,a comprehensive evaluation of these inertia and damping effects is conducted using a model-based phase-portrait approach.This method allows for an accurate assessment of critical clearing time(CCT)and critical clearing angle(CCA)across varying inertia and damping coefficients.Leveraging data obtained from the phase portrait,an artificial neural network(ANN)method is presented to model CCT and CCA accurately.This precise estimation of CCT enables the extension of practical operation time under faults compared to conservative assessments based on equal-area criteria(EAC),thereby fully exploiting the system's low-voltage-ride-through(LVRT)and fault-ride-through(FRT)capabilities.The theoretical transient analysis and estimation method proposed in this paper are validated through PSCAD/EMTDC simulations.展开更多
Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding...Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding annular domain(improved EAD)algorithm to estimate the domain of attraction(DA)of power systems containing multiple induction motors(IMs),whose improvements are concerned with relaxing the restriction on critical value and simplifying iteration steps.The proposed algorithm can systematically construct Lyapunov function for lossy power systems with IMs and their slip constraints.First,the extended Lyapunov stability theory and sum of squares(SOS)programming are presented,which are powerful tools to construct Lyapunov function.Second,the internal node model of IM is developed by an analogy with that of a synchronous generator,and a multi-machine power system model by eliminating algebraic variables is derived.Then,an improved EAD algorithm with SOS programming is proposed to estimate the DA for a power system considering the slip constraint of IM.Finally,the superiority of our method is demonstrated on two modified IEEE test cases.Simulation results show that the proposed algorithm can provide a better estimated DA and critical clearing slip for power systems with multiple IMs.展开更多
Voltage source converters(VSCs),equipped with Pf and Q-U droop characteristics,can support a power system from both frequency and voltage.Unfortunately,overcurrent and power angle instability are still challenging asp...Voltage source converters(VSCs),equipped with Pf and Q-U droop characteristics,can support a power system from both frequency and voltage.Unfortunately,overcurrent and power angle instability are still challenging aspects of VSCs under fault conditions.Therefore,fault current limitation and power angle stability are essential conditions for the safe operation of a VSC.Thus,the transient characteristics of a VSC are analyzed to guide transient control.Then,a transient control method for a VSC,considering both fault current limitation and power angle stability,is proposed.With the proposed method,power angle stability is realized by optimizing the P-f controller.On the basis of power angle control,the Q-U controller and inner current controller are improved to effectively suppress the fault current.Finally,relevant tests are performed to verify the proposed method.展开更多
The construction of waste rock dumps on existing tailing ponds has been put into practice in China to save precious land resources. This work focuses on the safety assessment of the Daheishan molybdenum mine waste roc...The construction of waste rock dumps on existing tailing ponds has been put into practice in China to save precious land resources. This work focuses on the safety assessment of the Daheishan molybdenum mine waste rock dump under construction on two adjoining tailings ponds. The consolidation of the tailings foundation and the filling quality of the waste rock are investigated by the transient electromagnetic method through detecting water-rich areas and loose packing areas, from which, the depth of phreatic line is also estimated. With such information and the material parameters, the numerical method based on shear strength reduction is applied to analyzing the overall stability of the waste rock dump and the tailings ponds over a number of typical cross sections under both current and designed conditions, where the complex geological profiles exposed by site investigation are considered. Through numerical experiments, the influence of soft lenses in the tailings and possible loose packing areas in the waste rock is examined. Although large displacements may develop due to the soft tailings foundation, the results show that the waste rock dump satisfies the safety requirements under both present and designed conditions.展开更多
The expansion of the estimated stability region plays an important role in the stability analysis of nonlinear systems.However,current literatures have not provided a complete mathematical description for this problem...The expansion of the estimated stability region plays an important role in the stability analysis of nonlinear systems.However,current literatures have not provided a complete mathematical description for this problem.This paper reveals that essentially the enlargement or the compression of the estimated stability region results directly from the diffeomorphism map,which is induced by the flow contained in the stability region.By proving that any integration algorithm with an order higher than one can approximately trace the flow of the system,a generalized methodology is proposed to construct various algorithms to realize the enlargement or the compression of the estimated stability region.With this methodology,two new algorithms based on symbolic calculation are suggested to reduce the computational burden.Furthermore,this methodology is applied to construct a scalable numerical algorithm to calculate the critical clearing time(CCT) of the power system for given faults.Tests on the IEEE 10-machine 39-bus system show that the computational results coincide well with the step-by-step simulation with high accuracy.展开更多
基金The authors extend their appreciation to the Deanship of Scientific Research at Jouf University for funding this work through research Grant No.(DSR-2021-02-0113).
文摘The effect of energy on the natural environment has become increasingly severe as human consumption of fossil energy has increased.The capacity of the synchronous generators to keep working without losing synchronization when the system is exposed to severe faults such as short circuits is referred to as the power system’s transient stability.As the power system’s safe and stable operation and mechanism of action become more complicated,higher demands for accurate and rapid power system transient stability analysis are made.Current methods for analyzing transient stability are less accurate because they do not account formisclassification of unstable samples.As a result,this paper proposes a novel approach for analyzing transient stability.The key concept is to use deep forest(DF)and a neighborhood rough reduction approach together.Using the neighborhood rough sets,the original feature space is obtained by creating many optimal feature subsets at various granularity levels.Then,by deploying the DF cascade structure,the mapping connection between the transient stability state and the features is reinforced.The weighted voting technique is used in the learning process to increase the classification accuracy of unstable samples.When contrasted to current methods,simulation results indicate that the proposed approach outperforms them.
基金supported by the EPSRC project‘Sustainable Urban Power Supply through Intelligent Control and Enhanced Restoration of AC/DC Networks'under Grant EP/T021985/1.
文摘This paper presents a quantitative assessment of the transient stability of grid-forming converters,considering current limitations,inertia,and damping effects.The contributions are summarized in two main aspects:First,the analysis delves into transient stability under a general voltage sag scenario for a converter subject to current limitations.When the voltage sag exceeds a critical threshold,transient instability arises,with its severity influenced by the inertia and damping coefficients within the swing equation.Second,a comprehensive evaluation of these inertia and damping effects is conducted using a model-based phase-portrait approach.This method allows for an accurate assessment of critical clearing time(CCT)and critical clearing angle(CCA)across varying inertia and damping coefficients.Leveraging data obtained from the phase portrait,an artificial neural network(ANN)method is presented to model CCT and CCA accurately.This precise estimation of CCT enables the extension of practical operation time under faults compared to conservative assessments based on equal-area criteria(EAC),thereby fully exploiting the system's low-voltage-ride-through(LVRT)and fault-ride-through(FRT)capabilities.The theoretical transient analysis and estimation method proposed in this paper are validated through PSCAD/EMTDC simulations.
基金supported by the Department of Science,and Technology of Guangdong Province under Grant No.2023 A1515240019。
文摘Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding annular domain(improved EAD)algorithm to estimate the domain of attraction(DA)of power systems containing multiple induction motors(IMs),whose improvements are concerned with relaxing the restriction on critical value and simplifying iteration steps.The proposed algorithm can systematically construct Lyapunov function for lossy power systems with IMs and their slip constraints.First,the extended Lyapunov stability theory and sum of squares(SOS)programming are presented,which are powerful tools to construct Lyapunov function.Second,the internal node model of IM is developed by an analogy with that of a synchronous generator,and a multi-machine power system model by eliminating algebraic variables is derived.Then,an improved EAD algorithm with SOS programming is proposed to estimate the DA for a power system considering the slip constraint of IM.Finally,the superiority of our method is demonstrated on two modified IEEE test cases.Simulation results show that the proposed algorithm can provide a better estimated DA and critical clearing slip for power systems with multiple IMs.
基金supported in part by the National Natural Science Foundation of China(51907057 and 52077072)Technological Leading Talent of Hunan province(2019RS3014).
文摘Voltage source converters(VSCs),equipped with Pf and Q-U droop characteristics,can support a power system from both frequency and voltage.Unfortunately,overcurrent and power angle instability are still challenging aspects of VSCs under fault conditions.Therefore,fault current limitation and power angle stability are essential conditions for the safe operation of a VSC.Thus,the transient characteristics of a VSC are analyzed to guide transient control.Then,a transient control method for a VSC,considering both fault current limitation and power angle stability,is proposed.With the proposed method,power angle stability is realized by optimizing the P-f controller.On the basis of power angle control,the Q-U controller and inner current controller are improved to effectively suppress the fault current.Finally,relevant tests are performed to verify the proposed method.
基金Projects(51209118,71373245)supported by the National Natural Science Foundation of ChinaProject(2014JBKY01)supported by the Fundamental Research Funds for CASST,China
文摘The construction of waste rock dumps on existing tailing ponds has been put into practice in China to save precious land resources. This work focuses on the safety assessment of the Daheishan molybdenum mine waste rock dump under construction on two adjoining tailings ponds. The consolidation of the tailings foundation and the filling quality of the waste rock are investigated by the transient electromagnetic method through detecting water-rich areas and loose packing areas, from which, the depth of phreatic line is also estimated. With such information and the material parameters, the numerical method based on shear strength reduction is applied to analyzing the overall stability of the waste rock dump and the tailings ponds over a number of typical cross sections under both current and designed conditions, where the complex geological profiles exposed by site investigation are considered. Through numerical experiments, the influence of soft lenses in the tailings and possible loose packing areas in the waste rock is examined. Although large displacements may develop due to the soft tailings foundation, the results show that the waste rock dump satisfies the safety requirements under both present and designed conditions.
基金supported by the National Natural Science Foundation (Grant Nos 50525721, 50595411)
文摘The expansion of the estimated stability region plays an important role in the stability analysis of nonlinear systems.However,current literatures have not provided a complete mathematical description for this problem.This paper reveals that essentially the enlargement or the compression of the estimated stability region results directly from the diffeomorphism map,which is induced by the flow contained in the stability region.By proving that any integration algorithm with an order higher than one can approximately trace the flow of the system,a generalized methodology is proposed to construct various algorithms to realize the enlargement or the compression of the estimated stability region.With this methodology,two new algorithms based on symbolic calculation are suggested to reduce the computational burden.Furthermore,this methodology is applied to construct a scalable numerical algorithm to calculate the critical clearing time(CCT) of the power system for given faults.Tests on the IEEE 10-machine 39-bus system show that the computational results coincide well with the step-by-step simulation with high accuracy.
