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
The stability of a voltage source converters(VSC)system based on phase-locked loop(PLL)is very important issue during asymmetric grid faults.This paper establishes a transient synchronous stability model of a dual-seq...The stability of a voltage source converters(VSC)system based on phase-locked loop(PLL)is very important issue during asymmetric grid faults.This paper establishes a transient synchronous stability model of a dual-sequence PLL-based VSC system during low voltage ride-through by referring to the equivalent rotor swing equation of syn-chronous generators.Based on the model,the synchronization characteristics of the VSC system under asymmetric grid faults are described,and the interaction mechanisms,as well as the transient instability phenomena of positive and negative sequence PLL during asymmetric faults are explained.Using the equal area criterion,the influences of sequence control switching action,detection delay,and interaction between the positive and negative sequence PLL on the transient synchronous stability of the VSC system are analyzed,respectively.In addition,a transient stabil-ity assessment criterion based on the critical fault clearance angle and time and an enhancement control strategy based on the improved positive and negative sequence PLL are proposed.Finally,the analytical results are validated through simulation and experiments.展开更多
Multiport magnetic network energy routers(MNERs)are a key technology in the energy internet that can improve the consumption level of renewable energy,realize the integration of source-grid-load-storage,and ensure the...Multiport magnetic network energy routers(MNERs)are a key technology in the energy internet that can improve the consumption level of renewable energy,realize the integration of source-grid-load-storage,and ensure the stable operation of power systems.However,the power grid may break down,causing the grid currents to exceed the safe threshold and the DC bus voltages to fluctuate,thereby threatening the stability of the power system.A coordinated low-voltage ride-through(LVRT)control strategy for an MNER-based grid connection system is proposed.The proposed control strategy can provide significant LVRT capability for an MNER-based grid-connection system and maintain the DC bus voltage of each port at the rated value.A simulation is conducted using the PLECS platform,and the results validate the effectiveness of the proposed coordinated LVRT control strategy.展开更多
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 in part by the National Natural Science Foundation of China under Grant 51977019in part by the Joint Research Fund in Smart Grid(U1966208)under cooperative agreement between the National Natural Science Foundation of China and State Grid Corporation of China.
文摘The stability of a voltage source converters(VSC)system based on phase-locked loop(PLL)is very important issue during asymmetric grid faults.This paper establishes a transient synchronous stability model of a dual-sequence PLL-based VSC system during low voltage ride-through by referring to the equivalent rotor swing equation of syn-chronous generators.Based on the model,the synchronization characteristics of the VSC system under asymmetric grid faults are described,and the interaction mechanisms,as well as the transient instability phenomena of positive and negative sequence PLL during asymmetric faults are explained.Using the equal area criterion,the influences of sequence control switching action,detection delay,and interaction between the positive and negative sequence PLL on the transient synchronous stability of the VSC system are analyzed,respectively.In addition,a transient stabil-ity assessment criterion based on the critical fault clearance angle and time and an enhancement control strategy based on the improved positive and negative sequence PLL are proposed.Finally,the analytical results are validated through simulation and experiments.
基金Supported by the National Key Research and Development Program of China(2022YFE0196300)Science,Technology&Innovation Funding Authority(STDF)(46505).
文摘Multiport magnetic network energy routers(MNERs)are a key technology in the energy internet that can improve the consumption level of renewable energy,realize the integration of source-grid-load-storage,and ensure the stable operation of power systems.However,the power grid may break down,causing the grid currents to exceed the safe threshold and the DC bus voltages to fluctuate,thereby threatening the stability of the power system.A coordinated low-voltage ride-through(LVRT)control strategy for an MNER-based grid connection system is proposed.The proposed control strategy can provide significant LVRT capability for an MNER-based grid-connection system and maintain the DC bus voltage of each port at the rated value.A simulation is conducted using the PLECS platform,and the results validate the effectiveness of the proposed coordinated LVRT control strategy.
