The introduction of fully controlled devices to build hybrid line commutated converter(H-LCC)has become a new idea to solve the commutation failure.However,existing H-LCC has not considered the implementation of a tar...The introduction of fully controlled devices to build hybrid line commutated converter(H-LCC)has become a new idea to solve the commutation failure.However,existing H-LCC has not considered the implementation of a targeted firing angle control strategy during AC faults,with the objective of enhancing their power transmission and fault response performance.For this reason,this paper proposes an optimized control method for firing angle of H-LCC,designated as flexible virtual firing(FVF).This method first analyzes the influence of alterations in firing angle on reactive power,commutation process and associated action paths.By combining prediction and dynamic search,it optimizes the natural commutation process through the utilization of dynamic boundary and minimum commutation area difference.This can mitigate the impact of AC faults on H-LCC and DC system,thereby improving power transmission and defense to commutation failure,which is beneficial for improving the stability of AC/DC power grids.Finally,the simulation results in PSCAD/EMTDC verify the effectiveness of the proposed method.展开更多
Earlier studies have reported some calculation methods for commutation failure fault level(CFFL) in line-commutated-converter based high-voltage direct current(LCCHVDC) system under single-line-to-ground(SLG) faults. ...Earlier studies have reported some calculation methods for commutation failure fault level(CFFL) in line-commutated-converter based high-voltage direct current(LCCHVDC) system under single-line-to-ground(SLG) faults. The accuracy of earlier methods is limited because they only consider the commutating voltage drop and phase shift, while neglecting the DC current variation. Hence, this paper proposes a CFFL calculation method under SLG faults considering DC current variation, for better planning and designing of LCC-HVDC systems. First, the fault commutating voltage magnitude and phase shift are calculated. Then, the fault DC voltage during different commutation processes is deduced. Based on the commutating voltage magnitude and phase shift, and DC voltage during different commutation processes under SLG faults, the characteristics of CFFL with different fault time are demonstrated and analyzed. Next, the transient time-domain response of the DC current after the fault is obtained based on the DC transmission line model. Discrete commutation processes are constructed based on the commutation voltage-time area rule to solve the extinction angle under different fault levels and fault time. Finally, the CFFL is calculated considering the fault time, commutating voltage drop, phase shift, and DC current variation. The accuracy of the proposed method compared with the traditional method is validated based on the CIGRE benchmark model in PSCAD/EMTDC.展开更多
基金supported in part by the National Key Research and Development Program of China(No.2021YFB2400900)the Integration Projects of National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2166602)+1 种基金the National Natural Science Foundation of China(No.52207200)the Science and Technology Innovation Program of Hunan Province(No.2024RC3113).
文摘The introduction of fully controlled devices to build hybrid line commutated converter(H-LCC)has become a new idea to solve the commutation failure.However,existing H-LCC has not considered the implementation of a targeted firing angle control strategy during AC faults,with the objective of enhancing their power transmission and fault response performance.For this reason,this paper proposes an optimized control method for firing angle of H-LCC,designated as flexible virtual firing(FVF).This method first analyzes the influence of alterations in firing angle on reactive power,commutation process and associated action paths.By combining prediction and dynamic search,it optimizes the natural commutation process through the utilization of dynamic boundary and minimum commutation area difference.This can mitigate the impact of AC faults on H-LCC and DC system,thereby improving power transmission and defense to commutation failure,which is beneficial for improving the stability of AC/DC power grids.Finally,the simulation results in PSCAD/EMTDC verify the effectiveness of the proposed method.
基金supported by the National Key Research and Development Program of China (No.2021YFB2400900)the Joint Funds of National Natural Science Foundation of China (No.U2166602)+1 种基金the National Natural Science Foundation of China (No.52207200)the Major Special Project of Hunan Province (No.2020GK1010)。
文摘Earlier studies have reported some calculation methods for commutation failure fault level(CFFL) in line-commutated-converter based high-voltage direct current(LCCHVDC) system under single-line-to-ground(SLG) faults. The accuracy of earlier methods is limited because they only consider the commutating voltage drop and phase shift, while neglecting the DC current variation. Hence, this paper proposes a CFFL calculation method under SLG faults considering DC current variation, for better planning and designing of LCC-HVDC systems. First, the fault commutating voltage magnitude and phase shift are calculated. Then, the fault DC voltage during different commutation processes is deduced. Based on the commutating voltage magnitude and phase shift, and DC voltage during different commutation processes under SLG faults, the characteristics of CFFL with different fault time are demonstrated and analyzed. Next, the transient time-domain response of the DC current after the fault is obtained based on the DC transmission line model. Discrete commutation processes are constructed based on the commutation voltage-time area rule to solve the extinction angle under different fault levels and fault time. Finally, the CFFL is calculated considering the fault time, commutating voltage drop, phase shift, and DC current variation. The accuracy of the proposed method compared with the traditional method is validated based on the CIGRE benchmark model in PSCAD/EMTDC.
