With the increasing development of wind power,the scale of wind farms and unit capacity of wind turbines are getting larger and larger,and the impact of wind integration on power systems cannot be ignored.However,in m...With the increasing development of wind power,the scale of wind farms and unit capacity of wind turbines are getting larger and larger,and the impact of wind integration on power systems cannot be ignored.However,in most cases,the areas with a plenty of wind resources do not have strong grid structures.Furthermore,the characteristics of wind power dictate that wind turbines need to absorb reactive power during operation.Because of the strong correlation between voltage stability and systems' reactive power,the impacts of wind integration on voltage stability has become an important issue.Based on the power system simulation software DIgSILENT and combined analysis of actual practice,this paper investigates the impacts of two types of wind farms on voltage stability:namely a type of wind farms which are constituted by constant speed wind turbines based on common induction generators(IG) and another type of wind farms which are constituted by VSCF wind turbines based on doubly-fed induction generators(DFIG).Through investigation the critical fault clearing time is presented for different outputs of wind farms.Moreover,the impacts of static var compensator(SVC) and static synchronous compensator(STATCOM) on transient voltage stability in IG-based wind farms are studied to improve the security and stability of the Jiangsu power grid after the integration of large scale wind power.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
The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional...The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.展开更多
The computation of the unstable equilibrium point(UEP)is a key step involved in stability region estimation of nonlinear dynamic systems.A new continuation-based method to compute the UEPs of a power system with induc...The computation of the unstable equilibrium point(UEP)is a key step involved in stability region estimation of nonlinear dynamic systems.A new continuation-based method to compute the UEPs of a power system with induction motors is proposed.The mechanical torques of motors are changed to form a parameterized equation set.Then the solution curve of the equation set is traced by the continuation method from the stable equilibrium point to a UEP.The direction of mechanical torque change is varied to get multiple UEPs.The obtained UEPs are mostly type-1.Then fast assessment of induction motor stability is studied by approximating the stable manifolds of the UEPs.The method is tested in several systems and satisfactory results are obtained.展开更多
文摘With the increasing development of wind power,the scale of wind farms and unit capacity of wind turbines are getting larger and larger,and the impact of wind integration on power systems cannot be ignored.However,in most cases,the areas with a plenty of wind resources do not have strong grid structures.Furthermore,the characteristics of wind power dictate that wind turbines need to absorb reactive power during operation.Because of the strong correlation between voltage stability and systems' reactive power,the impacts of wind integration on voltage stability has become an important issue.Based on the power system simulation software DIgSILENT and combined analysis of actual practice,this paper investigates the impacts of two types of wind farms on voltage stability:namely a type of wind farms which are constituted by constant speed wind turbines based on common induction generators(IG) and another type of wind farms which are constituted by VSCF wind turbines based on doubly-fed induction generators(DFIG).Through investigation the critical fault clearing time is presented for different outputs of wind farms.Moreover,the impacts of static var compensator(SVC) and static synchronous compensator(STATCOM) on transient voltage stability in IG-based wind farms are studied to improve the security and stability of the Jiangsu power grid after the integration of large scale wind power.
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This work was supported in part by the National Natural Science Foundation of China under Grant No.51807128State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources under Grant No.LAPS20017.
文摘The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.
文摘The computation of the unstable equilibrium point(UEP)is a key step involved in stability region estimation of nonlinear dynamic systems.A new continuation-based method to compute the UEPs of a power system with induction motors is proposed.The mechanical torques of motors are changed to form a parameterized equation set.Then the solution curve of the equation set is traced by the continuation method from the stable equilibrium point to a UEP.The direction of mechanical torque change is varied to get multiple UEPs.The obtained UEPs are mostly type-1.Then fast assessment of induction motor stability is studied by approximating the stable manifolds of the UEPs.The method is tested in several systems and satisfactory results are obtained.
