Grid-Friendly Transformer Magnetization - Siemens SINAMICS S120 System Manual
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Also See for SINAMICS S120:
- Function manual (1094 pages) ,
- Diagnostic manual (947 pages) ,
- Manual (848 pages)
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Detailed descriptions of the function modules
6.1 Additional closed-loop controls for current-controlled operation
In most applications, a setpoint other than zero does not make sense. During an FRT, a
possibly required non-symmetrical support current is directly injected internally (p5509[8]). In
the default setting of the dynamic grid support with p5500.3 = 1, the negative sequence
system control is automatically activated, in order to guarantee current symmetry even for 2-
phase grid faults.
A negative sequence system in the grid voltage or grid current is associated with power
pulsations, which result in the corresponding oscillations in the DC link voltage. However, in
order to dynamically control the average value of the DC link voltage (which is actually the
decisive value), V
Note
The negative sequence system control increases the computational load and reduces the
ruggedness of the control, as additional natural resonance effects occur. As a consequence,
the controller should only be activated when required.
6.1.5
Grid-friendly transformer magnetization
Background
If the primary side of the transformer represents the system connection point, then when
switching-in, a type of transformer pre-charging is required in order to avoid impermissible
inrush currents and grid flicker. The function block uses the power available in the DC link to
establish a voltage at the transformer terminals with the correct phase assignment. After this,
the main switch can be closed in an almost no-current condition.
Application
Adapted transformer data must be specified (p5436, p5492) if the transformer model (r5497,
r5498) is used, for example, for voltage control or a current DC component controller is
active (p3650 or p5436). Transformer data identification is not required for pure transformer
magnetization.
The transformer parameters (p5436, p5492) are appropriately preassigned for the relevant
Active Line Module power rating. If no applicable data are available, or can be measured
(also see Section "Current DC component controller"), then we recommend that the default
values are kept.
If the pre-charging circuit of an application only generates a low DC link voltage, which is not
sufficient to fully magnetize the transformer (modulation depth r0074 at its limit), then the
target value for the magnetization can be reduced (p5494[0]). When closing the grid
contactor, the residual magnetization required only creates a relatively low and generally
permissible recharging current surge.
Typical signs of an excessively low V
overmodulation (r0074 > 100 %).
The maximum current while magnetizing can be monitored in order to avoid overloading the
precharging circuit (p5494[1]). This means that an attempt to magnetize an inadvertently
grounded transformer can be canceled in a timely manner, for example.
54
is suitably filtered using an adjustable bandstop filter (p3645).
dc
are high phase currents as a result of operation with
dc
System Manual, 04/2015, A5E03347436A
Grid infeed
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