Abstract：This paper proposes and builds a novel hybrid high voltage direct current system, in which the rectifier side is made up of the line commutated converter(LCC) and the inverter side is composed of the modular multilevel converter(MMC). This system combines the merits of both LCC and MMC. The steady-state control stratedy and start-up stratedy are proposed based on the deduced quasi-steady state mathematic model. High power diode is installed in the DC outlet of the inverter side to block the fault current paths which could remedy the defect that the MMC are unable to clear up DC faults. A hybrid HVDC simulation system is built in PSCAD/EMTDC, and the effectiveness of the proposed steady-state control strategy and start-up strategy are illustrated. And meanwhile the technical advantage that MMC does not exist commutation failure is proved. Moreover, simulation results confirm the feasibility that the high power diode installed in the dc outlet of the inverter side could block the fault current paths.
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2013, Vol. 28 
