Description

The 2-winding saturable transformer adds modelling of saturation and hysteresis to the linear transformer at the expense of some computation time.

Table of Contents

Mask and Parameters

General Parameters

Description	Use this field to add all kinds of information about the component
Flux-current 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 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 connection	Winding type Y ground: Grounded Y connection (can use the internal neutral impedance specified in the other tab) Y floating: Floating Y connection Y neutral: Y connection with impedance connected at the input pin N1 or N2 Delta lead: Delta connection with lead of 30° Delta ground: Grounded delta connection (Phase C is grounded) Delta lag: Delta connection with lag of 30°
Voltage (rmsLL)	Rated voltage of the winding (kV) Y connections: Voltage expressed in kV rms LL Delta connections: Voltage expressed in kV rms LL
R1, R2	Leakage resistance of the winding (Ω)
L1, L2	Leakage inductance of the winding (H)

Neutral Impedance Parameters

R1, R2	Neutral resistance of the winding; only applies to Y ground (Ω)
L1, L2	Neutral inductance of the winding; only applies to Y ground (H)
C1, C2	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 3-phase 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 current-flux 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 current-flux 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)

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

Net_1	Primary winding connection (supports only 3-phase connections)
Net_2	Secondary winding connection (supports only 3-phase connections)
Net_N1	Neutral connection for primary winding (supports only 1-phase connections)
Net_N2	Neutral connection for secondary winding (supports only 1-phase connections)

Inputs

None

Outputs

None

Sensors

FLUX(a,b,c)	Magnetization flux for each phase (V.s)
ILMAG(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)
SEG(a,b,c)	Segment number of the saturation curve In the saturation model, the numbering is always positive starting at 1 for the last segment in the negative saturation zone. In the hysteresis model, the numbering is positive/negative starting at 1/-1 in the positive/negative saturation zone. In the hysteresis zone, it takes a null value.

References

«Hysteresis Modeling in the Matlab/Power System Blockset», Silvano Casoria, Patrice Brunelle, Gilbert Sybille, Mathematics and Computers in Simulation, Volume 63, Issues 3-5, Pages 237-248

2-Winding 3-Phase Saturable Transformer