Virtor(VSG)technology is widely investigated and applied for dual synchronous generatoubly-fed induction generators(DFIGs)to provide virtual inertia.However,under grid faults,the conventional VSG-based DFIG faces chal...Virtor(VSG)technology is widely investigated and applied for dual synchronous generatoubly-fed induction generators(DFIGs)to provide virtual inertia.However,under grid faults,the conventional VSG-based DFIG faces challenges of transient overcurrent and instability.The critical limitation for grid-forming DFIGs to withstand serious grid faults is the rotor-side converter(RSC)’s inability to quickly generate proper rotor voltage to counteract transient electromotive force(EMF),which results in transient overcurrent and damage to the RSC.To fill this gap,this study introduces a novel low-voltage ride-through(LVRT)control strategy for the grid-forming DFIG under symmetrical grid fault conditions.To mitigate transient overcurrent,the core mechanism is to regulate the rotor flux linkage to align with the stator flux linkage in an optimal proportion.Under the proposed control strategy,both post-fault rotor current and required rotor voltage are constrained within operational limits.Moreover,fluctuations in electromagnetic torque are efficiently suppressed during grid disturbances.Consequently,the dynamic stability and power support capacity of the DFIG system remain intact throughout the transient process.Finally,simulation studies and experimental results are provided to verify the feasibility of the proposed approach.展开更多
A wind-turbine power system is often challenged by voltage instability,reactive power imbalance,and limited fault ride-through capability under grid disturbances.Doubly Fed Induction Generator based wind farms,owing t...A wind-turbine power system is often challenged by voltage instability,reactive power imbalance,and limited fault ride-through capability under grid disturbances.Doubly Fed Induction Generator based wind farms,owing to their partial coupling with the grid,are particularly vulnerable to voltage dips and excessive reactive power absorption during fault events.This study proposes an adaptive control strategy based on Model Reference Adaptive Control integrated with stator flux-oriented vector control to regulate active and reactive power of a DFIG-based wind farm connected to a standard IEEE 9-bus power system under fault conditions.The proposed control scheme is developed and validated using detailed MATLAB/Simulink modeling under normal operation,symmetrical three-phase fault conditions,and post-fault recovery scenarios.A three-phase-to-ground fault is applied at the wind farm interconnection bus for a duration of 150 ms to evaluate transient performance.Simulation results demonstrate that the adaptive controller ensures fast power tracking,effective reactive power support,and enhanced voltage recovery compared to a conventional proportional–integral controller.Quantitatively,the proposed method improves voltage recovery time by approximately 45%,reduces active power overshoot by 38%,and lowers total harmonic distortion by 52% following fault clearance.Furthermore,the adaptive controller maintains stable operation under variations in wind speed and machine parameters without requiring retuning,highlighting its robustness against system uncertainties.The results confirm that the proposed control strategy significantly enhances fault ride-through capability,power quality,and dynamic stability of grid-interfaced wind farms.These findings demonstrate the practical applicability of adaptive control techniques for improving the reliability and resilience of modern power systems with high wind energy penetration.展开更多
The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the ...The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the DCV transient behavior of a PLL-based DFIG system under asymmetrical grid faults.First,by considering the coupling characteristics of positive and negative sequence(PNS)components,a nonlinear largesignal model of DCV is developed.Furthermore,the transient characteristics of DCV under varying parameters are analyzed using phase trajectory diagrams.In addition,the transient stability(TS)mechanism of DCV during asymmetrical faults is examined through an en-ergy function approach.The analysis indicates that the transient instability of DCV is primarily associated with the control characteristics of PNS PLLs,while the TS level of DCV is mainly determined by the power coordination control between the rotor side converter and grid side converter.Moreover,a coordinated control strategy is proposed to enhance the TS of DCV under asymmet-rical grid faults.Finally,both simulation and experimental results are presented to validate the theoretical analysis and the effectiveness of the proposed strategy.展开更多
Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency su...Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency support is terminated,the rotor speed should be restored to optimum for maximum power point tracking(MPPT).Existing IRCs utilize rotor speed recovery(RSR)strategies with a consistent power reference function.However,under real turbulent wind with alternate gusts and lulls,the consistent power reference function may fail to restore rotor speed or cause unexpected secondary frequency drop(SFD).In this regard,this paper proposes a novel adaptive RSR strategy that not only restores rotor speed via the aerodynamic power enhanced by wind gusts,but also stabilizes the turbine at wind lulls by tracking a suboptimal power curve.Experiments on a wind power-integrated power system testbed validate the proposed RSR strategy can successfully restore rotor speed while attenuating SFD under turbulent wind.展开更多
Fault Ride-Through （FRT） capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capa...Fault Ride-Through （FRT） capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capability and over-current protection of DFIG Wind Generators in MV networks is investigated. Simulation test cases using MATLAB-Simulink are implemented on a 365-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of the FRT capability on the protective relaying coordination in wind farms, showing that the FRT may work in situations where is were expected not to work, and then disabling the over-current protection, which should have worked in this situation.展开更多
We give a new result on the construction of K-frame generators for unitary systems by using the pseudo-inverses of involved operators,which provides an improvement to one known result on this topic.We also introduce t...We give a new result on the construction of K-frame generators for unitary systems by using the pseudo-inverses of involved operators,which provides an improvement to one known result on this topic.We also introduce the concept of K-woven generators for unitary systems,by means of which we investigate the weaving properties of K-frame generators for unitary systems.展开更多
This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational ...This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational efficiencies,and technological advancements.Linear generators,such as Induction,permanent magnet synchronous,and switched reluctance types,are highlighted for their direct conversion capability,eliminating the need for mechanical gearboxes.Rotary Induction generators,permanent magnet synchronous generators,and doubly-fed Induction generators are evaluated for their established engineering principles and integration with existing grid infrastructure.The paper discusses the historical development,environmental benefits,and ongoing advancements in wave energy technologies,emphasizing the increasing feasibility and scalability of wave energy as a renewable source.Through a comprehensive analysis,this review provides insights into the current state and future prospects of electrical generators in wave energy conversion,underscoring their potential to significantly reduce reliance on fossil fuels and mitigate environmental impacts.展开更多
基金supported by the National Natural Science Foundation of China(No.52477195,No.U25B20204,No.52437009).
文摘Virtor(VSG)technology is widely investigated and applied for dual synchronous generatoubly-fed induction generators(DFIGs)to provide virtual inertia.However,under grid faults,the conventional VSG-based DFIG faces challenges of transient overcurrent and instability.The critical limitation for grid-forming DFIGs to withstand serious grid faults is the rotor-side converter(RSC)’s inability to quickly generate proper rotor voltage to counteract transient electromotive force(EMF),which results in transient overcurrent and damage to the RSC.To fill this gap,this study introduces a novel low-voltage ride-through(LVRT)control strategy for the grid-forming DFIG under symmetrical grid fault conditions.To mitigate transient overcurrent,the core mechanism is to regulate the rotor flux linkage to align with the stator flux linkage in an optimal proportion.Under the proposed control strategy,both post-fault rotor current and required rotor voltage are constrained within operational limits.Moreover,fluctuations in electromagnetic torque are efficiently suppressed during grid disturbances.Consequently,the dynamic stability and power support capacity of the DFIG system remain intact throughout the transient process.Finally,simulation studies and experimental results are provided to verify the feasibility of the proposed approach.
文摘A wind-turbine power system is often challenged by voltage instability,reactive power imbalance,and limited fault ride-through capability under grid disturbances.Doubly Fed Induction Generator based wind farms,owing to their partial coupling with the grid,are particularly vulnerable to voltage dips and excessive reactive power absorption during fault events.This study proposes an adaptive control strategy based on Model Reference Adaptive Control integrated with stator flux-oriented vector control to regulate active and reactive power of a DFIG-based wind farm connected to a standard IEEE 9-bus power system under fault conditions.The proposed control scheme is developed and validated using detailed MATLAB/Simulink modeling under normal operation,symmetrical three-phase fault conditions,and post-fault recovery scenarios.A three-phase-to-ground fault is applied at the wind farm interconnection bus for a duration of 150 ms to evaluate transient performance.Simulation results demonstrate that the adaptive controller ensures fast power tracking,effective reactive power support,and enhanced voltage recovery compared to a conventional proportional–integral controller.Quantitatively,the proposed method improves voltage recovery time by approximately 45%,reduces active power overshoot by 38%,and lowers total harmonic distortion by 52% following fault clearance.Furthermore,the adaptive controller maintains stable operation under variations in wind speed and machine parameters without requiring retuning,highlighting its robustness against system uncertainties.The results confirm that the proposed control strategy significantly enhances fault ride-through capability,power quality,and dynamic stability of grid-interfaced wind farms.These findings demonstrate the practical applicability of adaptive control techniques for improving the reliability and resilience of modern power systems with high wind energy penetration.
基金supported in part by Smart Grid-National Science and Technology Major Project(No.2024ZD0801400)Science and technology projects of State Grid Corporation of China(No.52272224000V).
文摘The transient behavior of DC-link voltage(DCV)significantly affects the low-voltage ride-through for phase-locked loop(PLL)-based grid-connected doubly-fed induction generator(DFIG)systems.This study investigates the DCV transient behavior of a PLL-based DFIG system under asymmetrical grid faults.First,by considering the coupling characteristics of positive and negative sequence(PNS)components,a nonlinear largesignal model of DCV is developed.Furthermore,the transient characteristics of DCV under varying parameters are analyzed using phase trajectory diagrams.In addition,the transient stability(TS)mechanism of DCV during asymmetrical faults is examined through an en-ergy function approach.The analysis indicates that the transient instability of DCV is primarily associated with the control characteristics of PNS PLLs,while the TS level of DCV is mainly determined by the power coordination control between the rotor side converter and grid side converter.Moreover,a coordinated control strategy is proposed to enhance the TS of DCV under asymmet-rical grid faults.Finally,both simulation and experimental results are presented to validate the theoretical analysis and the effectiveness of the proposed strategy.
基金supported by National Natural Science Foundation of China(51977111)the Six Talent Peaks High-level Talent Project in Jiangsu Province(XNY-025)the Special Fund of Jiangsu Province for Transformation of Scientific and Technological Achievements(BA2019045).
文摘Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency support is terminated,the rotor speed should be restored to optimum for maximum power point tracking(MPPT).Existing IRCs utilize rotor speed recovery(RSR)strategies with a consistent power reference function.However,under real turbulent wind with alternate gusts and lulls,the consistent power reference function may fail to restore rotor speed or cause unexpected secondary frequency drop(SFD).In this regard,this paper proposes a novel adaptive RSR strategy that not only restores rotor speed via the aerodynamic power enhanced by wind gusts,but also stabilizes the turbine at wind lulls by tracking a suboptimal power curve.Experiments on a wind power-integrated power system testbed validate the proposed RSR strategy can successfully restore rotor speed while attenuating SFD under turbulent wind.
文摘Fault Ride-Through （FRT） capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capability and over-current protection of DFIG Wind Generators in MV networks is investigated. Simulation test cases using MATLAB-Simulink are implemented on a 365-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of the FRT capability on the protective relaying coordination in wind farms, showing that the FRT may work in situations where is were expected not to work, and then disabling the over-current protection, which should have worked in this situation.
基金Supported by NSFC(Nos.12361028,11761057)Science Foundation of Jiangxi Education Department(Nos.GJJ202302,GJJ202303,GJJ202319).
文摘We give a new result on the construction of K-frame generators for unitary systems by using the pseudo-inverses of involved operators,which provides an improvement to one known result on this topic.We also introduce the concept of K-woven generators for unitary systems,by means of which we investigate the weaving properties of K-frame generators for unitary systems.
文摘This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational efficiencies,and technological advancements.Linear generators,such as Induction,permanent magnet synchronous,and switched reluctance types,are highlighted for their direct conversion capability,eliminating the need for mechanical gearboxes.Rotary Induction generators,permanent magnet synchronous generators,and doubly-fed Induction generators are evaluated for their established engineering principles and integration with existing grid infrastructure.The paper discusses the historical development,environmental benefits,and ongoing advancements in wave energy technologies,emphasizing the increasing feasibility and scalability of wave energy as a renewable source.Through a comprehensive analysis,this review provides insights into the current state and future prospects of electrical generators in wave energy conversion,underscoring their potential to significantly reduce reliance on fossil fuels and mitigate environmental impacts.
