Abstract
In this paper, a hybrid high voltage direct current transmission system containing a line commutated converter and a voltage source converter is developed. To enhance the robustness of the hybrid transmission system against direct current short-circuit faults, resistive-type superconducting fault current limiters are applied, and the effectiveness of this approach is assessed. Related mathematical models are built, and the theoretical functions of the proposed approach are expounded. According to the transient simulations in MATLAB software, the results demonstrate that: (i) The superconducting fault current limiter at the voltage source converter station enables to very efficiently mitigate the fault transients, and owns an enhanced current-limiting ability for handling the short-line faults. (ii) The superconducting fault current limiter at the line commutated converter station is able to mildly limit the fault current and alleviate the voltage drop, and its working performance has a low sensitivity to the fault location. At the end of the study, a brief scheme design of the resistive-type superconducting fault current limiters is achieved. In conclusion, the application feasibility of the proposed approach is well confirmed.
Highlights
In recent years, hybrid high voltage direct voltage (HVDC) technology has received continuously increasing attention, and it is known as an advanced option for long distance as well as large-scale power transmission [1,2]
For promoting the development of hybrid HVDC technology, scholars have conducted some fundamental researches, which focus on the measure of alternating current (AC) system strength and the small-signal dynamics [3,4]
For the analytical model of the hybrid HVDC system, this study mainly considers the the following factors: (i) The two AC grids are represented by equivalent AC voltage sources with following factors: (i) The two AC grids are represented by equivalent AC voltage sources with series series impedances [20]. (ii) The DC transmission line is represented by an equivalent “resistanceimpedances [20]. (ii) The DC transmission line is represented by an equivalent “resistance-inductance inductance (R-L)” model. (iii) The line commutated converter (LCC) station adopts a constant DC current control to generate the (R-L)” model. (iii) The LCC station adopts a constant DC current control to generate the firing angle, firing angle, and the voltage source converter (VSC) station uses a direct current control mode [21]
Summary
Hybrid high voltage direct voltage (HVDC) technology has received continuously increasing attention, and it is known as an advanced option for long distance as well as large-scale power transmission [1,2]. The hybrid HVDC may have a complex fault issue, since the DC fault currents of the LCC and VSC stations have essential differences with each other. Concerning the DC fault current of the VSC station, it rises very fast and cannot be removed even though the power electronic switches are blocked, while the anti-parallel diodes act as a freewheeling bridge circuit to feed the fault current [5]. In [12,13], the performance behaviors of the resistive type SFCL on mitigating the commutation failure of a LCC-HVDC grid are studied. In [14,15,16,17], the SFCLs such as resistive-type, saturated iron-core-type, and hybrid-type are selected to inhibit the DC fault current of a pure VSC-HVDC network.
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