Micro-grid smooth switchover between
different operation modes is important for steady operation and reliable power
supply of micro-grid. In order to reduce the transient fluctuation of voltage
and frequency during switchover, this paper proposed a new switchover method
based on controller state following. When transferring to island mode, the
control method for inverter of storage device changed from PQ control to V/f
control. Before switchover, the output of V/f controller is always following
the output of PQ controller. So that the sudden change of output is avoided at
the moment of switchover. A micro-grid model with photovoltaic and battery is
built on DIgSILENT Power Factory simulation software, to simulate micro-grid
switchover from grid-connected mode to island mode. Results show this method can
effectively suppress the transient fluctuation of voltage and frequency, and
reduce the influence of transient process on power grid. This conclusion has
important practical significance on micro-grid smooth switchover from grid-con-
nected mode to island mode.
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