Abstract
The half bridge (HB) modular multilevel converter (MMC) technology is considered a breakthrough to mitigate the shortcomings of the conventional voltage source converter (VSC) in high-voltage direct-current (HVDC) grid application. However, interruption of the DC fault is still a challenge due to fast di/dt and extremely high levels of DC fault current. The fault interruption using a DC circuit breaker (DCCB) causes enormous energy dissipation and voltage stress across the DCCB. Therefore, the use of a fault current limiter is essential, and the superconducting fault current limiter (SFCL) is the most promising choice. Past literature has focused on the operating characteristics of DCCB or limiting characteristics of the SFCL. However, there is little understanding about the fault interruption and system recovery characteristics considering both DCCB and SFCL. In this paper, we have presented a comparative study on fault interruption and system recovery characteristics considering three types of fault limiting devices in combination with circuit breaker. The transient analyses of AC and DC system have been performed, to suggest the most preferable protection scheme. It has been concluded that, amongst the three fault limiting devices, the Hybrid SFCL in combination with circuit breaker, delivers the most desirable performance in terms of interruption time, recovery time, energy dissipation and voltage transients.
Highlights
DC fault interruption by use of external protection device has become imperative for the application of Half bridge (HB)-modular multilevel converter (MMC) based high-voltage direct-current (HVDC) grid [9,10]
Develop the hybrid DC circuit breaker (HCB) and install the circuit breaker in series with the Identify the minimum value of current limiting reactor that can provide sufficient time for Perform the transient analysis of the AC and DC systems according to the value of the current limiting reactor without applying the superconducting fault current limiter (SFCL)
4, we considered the effect of the size of current limiting reactor on time of resistive superconducting fault current limiter (R-SFCL) is considered to be 2 s based on the literature [38,39]
Summary
With the development of the voltage source converter (VSC), the realization of a high-voltage direct-current (HVDC) grid has become possible [1]. DC fault interruption by use of external protection device has become imperative for the application of HB-MMC based HVDC grid [9,10]. For the reliable and safe operation of a HVDC grid, the use of a HVDC circuit breaker (DCCB), which can quickly interrupt a DC fault current, is necessary [11,12]. A few prototypes of the DCCB have been proposed, but a commercial solution has not been developed yet owing to the constantly increasing levels of fault currents, limited performance of breaker components like the ultrafast disconnector switch (UFS) and arc suppression chamber, high overvoltage and large fault energy dissipation [14,15,16]. A superconducting fault current limiter (SFCL) shows zero electrical resistance and high current density under normal operation, whereas a high resistance and low current density under fault conditions can aid the operation of a circuit breaker [17,18]
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