This paper proposes a dual vector control scheme based on the sequence component separation strategy(SCSS)for second harmonic suppression in DC power.Firstly,an analytical model is established to depict the positive a...This paper proposes a dual vector control scheme based on the sequence component separation strategy(SCSS)for second harmonic suppression in DC power.Firstly,an analytical model is established to depict the positive and negative sequences of the controllable current source converter(CSC)under unbalanced grid conditions.Moreover,the generation mechanism of the DC power second harmonic component in the hybrid VSC-CSC HVDC system is demonstrated.This paper summarizes the impact of the modulation index(MI)and power factor(PF)on the operating characteristics of the modular multilevel converter(MMC)during the variation of the DC voltage.Based on the above analysis,the proposed control scheme extracts the sequence components of the CSC capacitor voltage and directly computes the sequence voltage reference value using instantaneous power.This approach effectively suppresses the second-harmonic component in DC power and significantly reduces the range of capacitor-voltage fluctuations in MMC submodules.Finally,an electromagnetic transient model of the hybrid HVDC system is constructed to validate the accuracy of the theoretical analysis and the effectiveness of the proposed control scheme.展开更多
基金supported by Smart GridNational Science and Technology Major Project(2025ZD0803700).
文摘This paper proposes a dual vector control scheme based on the sequence component separation strategy(SCSS)for second harmonic suppression in DC power.Firstly,an analytical model is established to depict the positive and negative sequences of the controllable current source converter(CSC)under unbalanced grid conditions.Moreover,the generation mechanism of the DC power second harmonic component in the hybrid VSC-CSC HVDC system is demonstrated.This paper summarizes the impact of the modulation index(MI)and power factor(PF)on the operating characteristics of the modular multilevel converter(MMC)during the variation of the DC voltage.Based on the above analysis,the proposed control scheme extracts the sequence components of the CSC capacitor voltage and directly computes the sequence voltage reference value using instantaneous power.This approach effectively suppresses the second-harmonic component in DC power and significantly reduces the range of capacitor-voltage fluctuations in MMC submodules.Finally,an electromagnetic transient model of the hybrid HVDC system is constructed to validate the accuracy of the theoretical analysis and the effectiveness of the proposed control scheme.
