Abstract
Damping circuits are installed inside the converter valve to limit commutation overshoots. They have significant effects on the valve’s turn-off performances, which should be carefully considered in parameter design. First, the calculation models for the turn-off process are discussed, including the conventional low frequency model and the broadband model. Then, it is found that high-frequency equipment parameters have significant effects on the transient valve voltage, which means that the conventional analytical methods based on low-frequency models is not suitable for damping circuit parameter design. The relationships between the turn-off performances and damping circuit parameters have also been analyzed in detail with the broadband model. To achieve better economic efficiency, this paper proposes a novel method for damping circuit parameter optimization, which combines the electromagnetic transient (EMT) calculation and the numerical optimization. Last, the case study is carried out based on a practical ±1100 kV ultra-high-voltage direct-current (UHVDC) transmission project, which proves the reliability and flexibility of the proposed method.
Highlights
The converter valve is the core equipment of high-voltage direct-current (HVDC) transmission projects
The main contributions of this paper are presented as follows: (1) A comparative analysis has been conducted to demonstrate the effects of high frequency parameters on the turn-off process; the results show that a broadband model is necessary for an accurate description of the turn-off performances, which is the basis for the damping circuit design
The turn-off performances of converter valve have been analyzed by the broadband model firstly
Summary
The converter valve is the core equipment of high-voltage direct-current (HVDC) transmission projects. References [8,18] adopted the method of ‘trial and error’ in their designs, based on the analytical relationships between the damping circuit parameters and the turn-off performances. The main contributions of this paper are presented as follows: (1) A comparative analysis has been conducted to demonstrate the effects of high frequency parameters on the turn-off process; the results show that a broadband model is necessary for an accurate description of the turn-off performances, which is the basis for the damping circuit design. (2) A novel optimization method for damping circuit parameters has been proposed; this method is derivative-free and fit for the cases where broadband models and unbalanced voltage distribution are considered; the validity and flexibility of the proposed optimization approach are verified and discussed.
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