Abstract For the hybrid cascaded ultra-high voltage direct current (UHVDC) transmission system composed of high and low valve, a DC voltage method suitable for modular multilevel converter (MMC) is proposed. Based on selecting a single MMC as a constant DC voltage control mode, the other power-controlled converters are added with graded auxiliary voltage control, which can accurately control DC power in steady state, and put in voltage auxiliary control in different stages according to different voltage fluctuations in dynamic state, the problems of DC over-voltage, under-voltage and long-term oscillation can be quickly suppressed. On this basis, the DC side of the multi-converters in the cascade structure is directly connected in parallel without smoothing reactor reactance, and to avoid the oscillation among the multi-converters, a DC damping control method is added. Finally, a simulation model of cascaded UHVDC transmission system is built using the real time digital simulator (RTDS) and simulation results demonstrate the correctness and validity of the proposed method.
SUI Shunke,CHANG Haotian,ZOU Qiang等. DC side control method of modular multilevel converter for hybrid cascaded ultra high voltage DC transmission system[J]. Electrical Engineering, 2023, 24(4): 57-62.
2023, Vol. 24 
