LVRT is short for Low Voltage Ride-Through and describes
the requirement that generating plants must continue to
operate through short periods of low grid voltage and not
disconnect from the grid.
Short-term voltage dips may occur, for example, when large
loads are connected to the grid or as a result of grid faults
like lightning strikes or short-circuits. In the past, renewable
generating plants such as wind turbines were allowed
to disconnect from the grid during such a fault and try to
reconnect after a certain period of time. Today, because
of the significant share of renewables, such a procedure
would be fatal. If too many generating plants disconnect at
the same time the complete network could break down, a
scenario which is also called a “blackout”. For this reason
the LVRT requirement has been established which is meant
to guarantee that the generating plants stay connected to
the grid. Additionally many grid codes demand that the
grid should be supported during voltage drops. Generating
plants can support the grid by feeding reactive current into
the network and so raise the voltage. Immediately after
fault clearance, the active power output must be increased
again to the value prior to the occurrence of the fault within
a specified period of time.
These requirements which at the beginning only applied
to wind turbines, now also have to be fulfilled by photovoltaic
systems (PV) and most recently, by combined heatand-
power plants (CHP).
Fig. 1 shows the result of a voltage drop test at a PV system.
In this diagram the voltage drops to about 20% of the nominal
voltage for a time of approx. 550ms. The PV inverter
recognizes the voltage drop and feeds a reactive current
of approx. 100% of the nominal voltage into the system for
LVRT is short for Low Voltage Ride-Through and describes
the requirement that generating plants must continue to
operate through short periods of low grid voltage and not
disconnect from the grid.
Short-term voltage dips may occur, for example, when large
loads are connected to the grid or as a result of grid faults
like lightning strikes or short-circuits. In the past, renewable
generating plants such as wind turbines were allowed
to disconnect from the grid during such a fault and try to
reconnect after a certain period of time. Today, because
of the significant share of renewables, such a procedure
would be fatal. If too many generating plants disconnect at
the same time the complete network could break down, a
scenario which is also called a “blackout”. For this reason
the LVRT requirement has been established which is meant
to guarantee that the generating plants stay connected to
the grid. Additionally many grid codes demand that the
grid should be supported during voltage drops. Generating
plants can support the grid by feeding reactive current into
the network and so raise the voltage. Immediately after
fault clearance, the active power output must be increased
again to the value prior to the occurrence of the fault within
a specified period of time.
These requirements which at the beginning only applied
to wind turbines, now also have to be fulfilled by photovoltaic
systems (PV) and most recently, by combined heatand-
power plants (CHP).
Fig. 1 shows the result of a voltage drop test at a PV system.
In this diagram the voltage drops to about 20% of the nominal
voltage for a time of approx. 550ms. The PV inverter
recognizes the voltage drop and feeds a reactive current
of approx. 100% of the nominal voltage into the system for
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