抄録
A STATCOM is expected to be suitable for use as voltage control equipment for a distribution system that needs to be controlled to suppress the voltage deviation caused by an increase in the number of photovoltaic energy sources. A Y-connection MMC is a promising alternative for the STATCOM circuit topology. However, it has been known that the Y-connection MMC cannot achieve capacitor voltage balance between phases with unbalance current output for compensating system voltage unbalance. To solve this problem, we propose a novel method to control the capacitor voltage in the case of an unbalance current output.
The proposed control involves feedforward and feedback zero sequence voltage control. The feedforward control prevents capacitor voltage unbalance between phases, which is caused by the unbalance current that the Y-connection MMC outputs. The feedback control cancels the remaining control error of the feedforward control.
We verified the performance of the control through transient simulation. The Y-connection MMC with the proposed control can achieve capacitor voltage balance between phases even when the Y-connection MMC outputs an unbalance current.
Additionally, we determined the maximum unbalance current output produced by the Y-connection MMC in relation to the rated capacitor voltage.
