Voltage collapses.
(c) The current rate change determined
by the difference between the voltage at
the inverter station and the inductance the
DC line.
.
(d) Between the fault occurring and the
current decreasing zero, the energy
unbalance between the and systems
accumulated and increases the voltage
across the converter
(e) The inverter controller needs consider the
potential for over-voltage across the inverter
and try prevent it, ensure fault ride
through. case fault the point of
connection (PoC) the power drops zero
because zero voltage
Udc: DC-link voltage.
(b) restore balance between and AC
sides the inverter section, the converter
controller increases the voltage reduce
the current zero.48
Barriers the uptake MVDC grids
Pac: Power transmitted from converter into
the grid. During fault, the DC-current
is controlled zero and thus the DC-link
voltage the converter increases due the
DC-line inductance
Idc: current through the DC-link
Pdc: Active power transmitted through the DC-
link
Usm: Voltage across the converter sub-modules
Figure 5-1 fault ride through process MVDC converter
Pac
ACfault
t
t
Udc inverter
rectifier
ΔUdc
Usm
a)
b)
e)
blocking voltage
t
t
Idc
ΔUdc
2Ldc
c)
Pdc
ΔEm
t
d)
(a) fault the grid causes the active power
delivered the side the converter to
suddenly drop zero
