MMC-MTDC Power Balance Control Strategy under Multi-factor Constraints
The traditional droop control cannot ensure the accurate distribution of the unbalance power and the stability of the DC voltage after the wind field power fluctuation.The causes of this problem need to be analyzed and solved.In view of this situation,the influence of wind power fluctuation on droop characteristics is analyzed by establishing a mathematical model of the converter station.Then,through the equivalent circuit model of multi-terminal flexible DC transmission,the influence of line impedance on voltage fluctuation is analyzed,and the power distribution weight coefficient is introduced to stabilize the DC voltage.The real-time power margin of the converter station under different wind speed fluctuation scenarios is also considered to avoid full load of the converter station.Based on the above analysis,an improved adaptive droop control strategy is proposed,which can adaptively modify the droop curve coefficient,so that the converter station can approximate the U-P characteristic curve to the optimal power allocation under the premise of ensuring voltage stability.Finally,a three-terminal MMC-MTDC system model including a wind farm is built on the PSCAD,and the simulation results show the effectiveness of the improved droop control strategy.
Multi-terminal flexible DC power transmissionline resistancepower marginactive power optimal distributionimproved droop control
NETL
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