Small signal analysis for DC bus voltage disturbance resistance of voltage source converter

Authors: YINGJIE WANG, XIAOJIE WU, PING LU, YONGLEI ZHANG

Abstract: The DC bus voltage of the voltage source converter (VSC) is prone to large fluctuation and even to losing its stability for the large mutation of grid voltage or DC-link loads. First the characteristics of two-step transmission to power in the VSC are analyzed, proving that it is inevitable for DC bus voltage fluctuation to occur when grid voltage or DC-link loads mutate. A new two-step feedforward control strategy is then put forward for curbing the fluctuation, which overcomes the shortcoming by which the traditional feedforward control strategy is affected for the performance of current control. The small signal models of nonfeedforward control, traditional feedforward control, and two-step feedforward control are established respectively for comparing their performance. It is certified that the two-step feedforward control maximizes the stability of the bus voltage without affecting current control. Finally, the experimental results verify the correctness of the new strategy and the theoretical analysis.

Keywords: DC bus voltage, small signal model, power balance, feedforward control, disturbance resistance

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