Abstract
Due to the low impedance characteristic of the high voltage direct current (HVDC) grid, the fault current rises extremely fast after a DC-side fault occurs, and this phenomenon seriously endangers the safety of the HVDC grid. In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker (MB), a fault current limiting hybrid DC circuit breaker (FCL-HCB) has been proposed in this paper, and it has the capability of bidirectional fault current limiting and fault current interruption. After the occurrence of the overcurrent in the HVDC grid, the current limiting circuit (CLC) of FCL-HCB is put into operation immediately, and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result. Compared with the traditional hybrid DC circuit breaker (HCB), the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device. Extensive simulations also verify the effectiveness of the proposed FCL-HCB.
Highlights
Compared with the traditional line commutated converter (LCC)-based high-voltage DC (HVDC) transmission systems, high voltage direct current (HVDC) grids based on modular multilevel converter (MMC) have more advantages, such as independent control of active and reactive power, easiness to form a multi-terminal network, power supply for passive networks, etc. [1]
Compared the proposed fault current limiting hybrid DC circuit breaker (FCL-hybrid DC circuit breaker (HCB)) with the traditional HCB, the peak value of the fault current is reduced by 35.63%, the energy consumption of the main breaker (MB) is reduced by 47.13%, and the energy dissipation time is shortened by 18.28%
During the fault current limiting and fault current interruption process of the FCL-HCB, the peak value of the fault current flowing through the DC line is about 5.6 kA, the fault current absorption time is about 7.6 ms, and the energy consumption of the arrester in the MB is about 16.6 MJ
Summary
Compared with the traditional line commutated converter (LCC)-based high-voltage DC (HVDC) transmission systems, HVDC grids based on modular multilevel converter (MMC) have more advantages, such as independent control of active and reactive power, easiness to form a multi-terminal network, power supply for passive networks, etc. [1]. The SSCB use the current-block capability of power electronic devices to interrupt fault current and it can operate extremely fast (within 1 ms) It requires high investment cost and may cause large power losses [7]. The HCB combines the advantages of the MCB and the SSCB, which has the characteristics of low conduction loss and fast action speed [9] It requires many semiconductor switches in series to withstand the transient interruption voltage (TIV), so the investment cost is relatively high. Shunt reactor is not significantly improved compared with the traditional ABB HCB To solve this problem, this paper proposes a fault current limiting hybrid DC circuit breaker (FCL-HCB).
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