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
Similar to synchronous generators(SGs),symmetrical short-circuit faults can reduce the stability margin of grid-forming renewable power generation(GFM-RPG),thereby heightening the risk of transient instability.While e...Similar to synchronous generators(SGs),symmetrical short-circuit faults can reduce the stability margin of grid-forming renewable power generation(GFM-RPG),thereby heightening the risk of transient instability.While existing studies primarily examine single-machine infinite-bus systems,this work explores transient stability challenges inherent in paralleled GFM-RPG systems.First,through rigorous mathematical derivation,it establishes that the transient characteristics of paralleled systems can still be effectively characterized by a second-order motion equation.Subsequently,by applying the extended equal area criterion(EEAC)and numerical solutions to differential equations,the study uncovers the governing principles behind the variations in the critical clearing angle(CCA)and critical clearing time(CCT)for the paralleled GFM-RPG system under various operating conditions.Finally,to mitigate potential instability risks,two corrective strategies,namely adaptive damping enhancement and power switching control,are proposed to improve the transient stability of the paralleled system during symmetrical faults.Simulation results confirm the accuracy of the theoretical analysis and demonstrates the effectiveness of the proposed 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 by Joint Research Fund in Smart Grid(No.U1966208)under cooperative agreement between the National Natural Science Foundation of China and State Grid Corporation of China.
文摘Similar to synchronous generators(SGs),symmetrical short-circuit faults can reduce the stability margin of grid-forming renewable power generation(GFM-RPG),thereby heightening the risk of transient instability.While existing studies primarily examine single-machine infinite-bus systems,this work explores transient stability challenges inherent in paralleled GFM-RPG systems.First,through rigorous mathematical derivation,it establishes that the transient characteristics of paralleled systems can still be effectively characterized by a second-order motion equation.Subsequently,by applying the extended equal area criterion(EEAC)and numerical solutions to differential equations,the study uncovers the governing principles behind the variations in the critical clearing angle(CCA)and critical clearing time(CCT)for the paralleled GFM-RPG system under various operating conditions.Finally,to mitigate potential instability risks,two corrective strategies,namely adaptive damping enhancement and power switching control,are proposed to improve the transient stability of the paralleled system during symmetrical faults.Simulation results confirm the accuracy of the theoretical analysis and demonstrates the effectiveness of the proposed strategy.
