科研之友
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摘要
A hybrid high voltage direct current system can combine the merits of both MMC and LCC, in which the rectifier side is made up of the modular multilevel converter(MMC) and the inverter side is composed of the line commutated converter(LCC). It is a new type of topology suitable for wind power transmission. The hybrid HVDC breaker is installed on the DC transmission line of the rectifier side to block the fault current paths which could remedy the limitation that the MMC is unable to clean up DC side faults. The DC-link fault characteristics of line-to-ground and line-to-line, as well as their effects on system are analyzed, and time sequence control strategy based on current characteristics is designed. A hybrid HVDC simulation system is built based on PSCAD softuware, and the advantage on stabilizing the voltage of converter side AC bus is simulated and analyzed. Moreover, the fault characteristics proposed is validated. Finally, Simulation results verify the time sequence control can effectively isolate the DC side fault.
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