Short-Circuit Current Calculation Method for Multi-Terminal VSC-HVDC Transmission Systems with Hybrid MMC
There are multiple converter stations in a multi-terminal voltage source converter-high voltage direct current(VSC-HVDC)transmission system,and the complex coupling relationship among converter stations makes the calculation of DC short-circuit cur-rent a challenge.For the scenarios of a multi-terminal VSC-HVDC transmission system containing hybrid modular multi-level converter(MMC),firstly the fault equivalent model of the hybrid MMC before and after DC fault ride-through is established,and the influence of DC fault ride-through on the short-circuit current of the multi-terminal VSC-HVDC transmission system is analyzed from the perspective of the change in circuit structure during DC fault ride-through of a hybrid MMC.Based on the superposition theorem,the concept of DC fault ride-through additional network is proposed.Then,a short-circuit current calculation method of the multi-terminal system containing hybrid MMC is proposed during DC fault ride-through,combining the approximate decoupling analytic calculation method of multi-terminal system and the concept of DC fault ride-through additional network.Finally,the electromagnetic transient simulation results based on PSCAD/EMTDC show that the maximum error of the short-circuit current values calculated within 6 ms of the fault occurrence is within±6%,and the proposed calculation method has good applicability.It provides a reference for the planning,design,and protection setting of multi-terminal VSC-HVDC transmission systems containing hybrid MMC.
multi-terminal VSC-HVDC transmission systemhybrid MMCDC fault ride-throughnetwork equivalenceshort-circuit current calculation
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