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3Winding 3Phase Saturable Transformer with Tap Changer
Mask and Parameters
General Parameters
Description  Use this field to add all kinds of information about the component 
FluxCurrent model  Model saturation only or saturation with hysteresis 
Iteration in saturation model  Enable or disable iteration to achieve more accurate results at the expense of computation time when the saturation segment changes 
Base primary/secondary/tertiary winding voltage (rmsLL)  Base value for PU conversion (kV). Voltage expressed in kV rms LL This base voltage and nominal voltage will change, if the corresponding winding connection switches between delta and Y. 
Base power (total)  Base value for PU conversion (MVA) 
Base frequency  Base value for PU conversion (Hz) 
Magnetization Impedance Parameters
 Rm: Equivalent resistance of iron losses of the magnetic circuit (Ω)
Winding Parameters
Primary/secondary/tertiary connection  Winding type

Voltage (rmsLL)  Rated voltage of the winding (kV)

R1, R2, R3  Leakage resistance of the winding (Ω) 
L1, L2, L3  Leakage inductance of the winding (H) 
Neutral Impedance Parameters
R1, R2, R3  Neutral resistance of the winding; only applies to Y ground (Ω) 
L1, L2, L3  Neutral inductance of the winding; only applies to Y ground (H) 
C1, C2, C3  Neutral capacitance of the winding; only applies to Y ground (F) 
Saturation Parameters
The saturation is characteristic of the core, thus of the winding and not the type of 3phase connection (Y, Delta or Zigzag). It is represented only for the magnetization branch (schematically using line segments).
Number of data points  Number of segments of the currentflux saturation curve; only the positive part of the curve must be specified, the negative part being completed by symmetry 
Saturation current  Current for each segment of the saturation curve; the origin (0,0) is implied (A) 
Saturation flux  Flux for each segment of the saturation curve; the origin (0.0,0.0) is implied (V.s) 
Hysteresis Parameters
The main hysteresis cycle is characterized by four parameters. It is measured in DC so as not to include the Foucault losses, which are considered by the parallel resistance (Rm). The initial trajectory is characterized by only one parameter, the initial flux. Two other special parameters serve to minimize the generation of internal nested loops, and their corresponding trajectories, saved in memory (e.g. the loops that are too small will be ignored and their trajectories modelized by a straight line segment).
This is useful since their number must be limited (100 which suffices in most simulated cases). Above this cycle (limited to ±Is), the saturation zone is entered. The saturation is then characterized either by a series of points on the curve or by an inductance that the curve approaches asymptotically. In this last case, the model generates automatically segments (in the positive and negative saturation zone) of equal length (Is).
Saturation data type  Determines if the saturation curve is calculated by the model or defined by a series of segments (Equation, Curve) 
Air core inductance  Value of the saturation inductance that the curve approaches asymptotically (H) 
Slope at Ic  Flux slope at coercive current (H) 
Coercitive current  Ic:  Positive coercive current at null flux (A) 
Saturation current  Is  Current value of the first point in the saturation zone (A) 
Current tolerance  Special parameter limiting the generation of minor nested loops. When the magnetizing current values at the last inversion point and the preceding inversion point are closer than the specified tolerance (in % of Ic), it is assumed that there is a displacement on a trajectory represented by a straight line segment. 
Remnant flux  Φr  Positive remnant flux at null current (V.s) 
Saturation flux  Φs  Flux value of the first point in the saturation zone (V.s) 
Flux tolerance  Special parameter limiting the generation of minor nested loops. When the flux values at the last inversion point and the preceding inversion point are closer than the specified tolerance (in % of Φs), it is assumed that there is a displacement on the current loop. 
Initial flux (peak)  Initial flux determining initial trajectory which is calculated by supposing that it has an inversion point on the main cycle (V.s) 
Number of points  Number of segments of the currentflux saturation curve; only the positive part of the curve must be specified, the negative part being completed by symmetry 
Saturation current  Current for each segment of the saturation curve; the first value must be equal to Is (A) 
Saturation flux  Flux for each segment of the saturation curve; the first value must be equal to Φs (V.s) 
Tap Changer Parameters
The tap changer effect is simulated by changing the transformer ratio.
Control type  Source of the command

Manual position  Manual position required; either a set point or initial value depending on the control type 
Number of taps  Number of tap(s); maximum 50 
Nominal tap  Tap position at which nominal values are set 
Tap size (% of base voltage)  Tap voltage increment value in reference to the primary base voltage (%) 
Temporization time  Minimum duration required for a signal order to start changing tap (s) 
Operation time  Time between tap changes (s) 
Ports, Inputs, Outputs and Signals Available for Monitoring
Ports
Net_1  Primary winding connection (supports only 3phase connections) 
Net_2  Secondary winding connection (supports only 3phase connections) 
Net_3  Tertiary winding connection (supports only 3phase connections) 
Net_N1  Neutral connection for primary winding (supports only 1phase connections) 
Net_N2  Neutral connection for secondary winding (supports only 1phase connections) 
Net_N3  Neutral connection for tertiary winding (supports only 1phase connections) 
Inputs
 U: Up control input; changes one position
 D: Down control input; changes one position
Outputs
 Pos: Tap position
Sensors
D  "Down one position" order from control input or internal command 
FLUX(a,b,c)  Magnetization flux for each phase (V.s) 
IMAG(a,b,c)  Magnetization current for each phase (A) 
IPRIM(a,b,c)  Primary current for each phase (A) 
ISEC2(a,b,c)  Secondary current for each phase (A) 
ISEC3(a,b,c)  Tertiary current for each phase (A) 
SEG(a,b,c):  Segment number of the saturation curve

Tap  Tap position 
U  "Up one position" order from control input or internal command 
References
«Hysteresis Modeling in the Matlab/Power System Blockset», Silvano Casoria, Patrice Brunelle, Gilbert Sybille, Mathematics and Computers in Simulation, Volume 63, Issues 35, Pages 237248
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