Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used t...Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.展开更多
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
文摘Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.
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.
