Description

The ARTEMiS-Transformer with Switched Saturable Core implements a 3-phase saturable transformer in Simscape Electrical Specialized Power Systems (SPS) model using a switched saturable core method instead of the current injection with delay of the native SPS transformer models. This type of model is used to solve instability problems of the current injection methods with delay.

Available models are zigzag-Y , Y-Y, Y-D (±30 deg.), in PU and SI versions.

The ARTEMiS-Transformer with Switched Saturable Core implements a 3-phase saturable transformer in SPS model using a switched saturable core method instead of the current injection with delay of the native SPS transformer models. The model is to be used in conjunction with the ARTEMiS GUIde block.

The model is based on the SPS transformer model for the linear part. The non-linear part, i.e. the saturation is modeled has a switched core inductance. In the linear region of operation, the first segment of the i=f(flux) characteristic is included in the ABCD state-space matrix and flux is monitored from there. Whenever the flux reaches the second (and last) segment of the i=f(flux) characteristic, an inductance is switched in parallel with the linear one and simulation continues with the new configuration of the circuit caused by this switching action.

Table of Contents

Mask and Parameters

Parameters (zig-zag)

NOTE: the ARTEMiS-Transformer with Switched Saturable Core only allows a two-segment saturation characteristic so only 3 pairs of points can be entered (including the (0,0) point).
Units	Specify the units used (SI or pu) for Zigzag Phase-Shifting Transformer block. Two different blocks must be used for SI or PU units.
Nominal power and frequency	The nominal power rating, in volt-amperes (VA), and nominal frequency, in hertz (Hz), of the transformer.
Primary (zigzag) nominal voltage Vp	The phase-to-phase nominal voltage in volts RMS, for the primary winding of the transformer.
Secondary nom. voltage phase shift	The phase-to-phase nominal voltage, in volts RMS, and the phase shift, in degrees, for the secondary winding of the transformer.
Winding 1 zig-zag [R1 L1]	The resistance and leakage inductance of the windings 1 of the single-phase transformers used to implement the primary winding of the Zigzag Phase-Shifting Transformer.
Winding 2 zig-zag [R2 L2]	The resistance and leakage inductance of the windings 2 of the single-phase transformers used to implement the primary winding of the Zigzag Phase-Shifting Transformer.
Winding 3 secondary [R3 L3]	The resistance and leakage inductance of the windings 3 of the single-phase transformers used to implement the secondary winding of the Zigzag Phase-Shifting Transformer.
Magnetization resistance Rm	This parameter is accessible only if the Saturable core parameter on the Configuration tab is selected.
Saturation characteristic:	The saturation characteristic for the saturable core. Specify a series of current/ flux pairs (in pu) starting with the pair (0,0).

Parameters (Y-D)

The ARTEMiS-Transformer with Switched Saturable Core only allows a two-segment saturation characteristic so only 3 pairs of points can be entered (including the (0,0) point).
Units	Specify the units used (SI or pu) for Zigzag Phase-Shifting Transformer block. Two different blocks must be used for SI or PU units.
Nominal power and frequency	The nominal power rating, in volt-amperes (VA), and nominal frequency, in hertz (Hz), of the transformer.
Primary (Y) nominal voltage Vp	The phase-to-phase nominal voltage in volts RMS, for the primary winding of the transformer. This winding is always connected in Y.
Secondary nom. voltage	The phase-to-phase nominal voltage, in volts RMS, for the secondary winding of the transformer.
Secondary winding (abc) connection	The type of connection for the secondary windings. Available connection are: Y-Y, and Y-D (±30 deg.). Note that the winding neutral point connection is always available at both primary and secondary winding.
Winding 1 impedance [R1 L1]	The resistance and leakage inductance of the windings 1 of the single-phase transformers used to implement the primary winding of the Zigzag Phase-Shifting Transformer.
Winding 2 impedance [R2 L2]	The resistance and leakage inductance of the windings 2 of the single-phase transformers used to implement the primary winding of the Zigzag Phase-Shifting Transformer.
Magnetization resistance Rm	This parameter is accessible only if the Saturable core parameter on the Configuration tab is selected.
Saturation characteristic	The saturation characteristic for the saturable core. Specify a series of current/ flux pairs (in pu) starting with the pair (0,0).

Advanced Parameters

Use SPS injection method	Disable the Switching Core Saturation and use standard SPS injection method to simulate saturation
Disable saturation	Disable the Switched Core saturation (only if Use SPS injection method is not selected)
Unique Global Tag	Unique tag within the COMPLETE model to route some internal flux signals inside the transformer model. If two ARTEMiS Switched Core transformer model with the same Unique Global Tag are in the same simulation model, an error will occur.

Examples

Example 1: Energization of a zig-zag transformer with a floating source

This example case makes the energization of a 3-phase zigzag-Y transformer on an inductive load. The load is has about 0.8 pu of active power 0.6 pu of reactive power. The transformer has an total impedance of 0.26 pu and is energized from rest with a balanced source of 1 pu of voltage.

The saturation curve is depicted on the next figure.

The particularity of this model is that it simply cannot be simulated in real-time with SPS only. If one tries to simulate this model with the current injection with delay method of SPS, the model is unstable, event at 0.1 µs!

With the ARTEMiS-Transformer with Switched Saturable Core, the model is stable and very accurate at time step of 30µs and more.

The following curves compare the simulation results of the model with ARTEMiS-Transformer with Switched Saturable Core at 30µs with one made with native SPS at 1µs, with an algebraic loop. This means that the solver becomes iterative in this case and not suitable for real-time simulation anyway. It can however be taken for off-line simulation reference.

The simulations are conducted with positive and negative angle phase shifts to verify the internal connection of the ARTEMiS models.

Input and Outputs

A+, B+, C+ (PM-type connectors)	1st winding of zigzag. Positive polarity zigzag winding connection.
A-, B-, C-: (PM-type connectors)	2nd winding of zigzag. Negative polarity zigzag winding connection.
a3, b3, c3: (PM-type connectors)	3rd (or secondary) winding connected in Y.
flux	core flux signals (size 3)

Characteristics and Limitations

The ARTEMiS-Transformer with Switched Saturable Core can only work with the ARTEMiS GUIde block present in the model.

The first reason is that the ARTEMiS saturable transformer models are used to provide the core flux readings required by the model.
The 2nd reason is that the damping properties of the ARTEMiS art5 solver are required to obtain

Direct Feedthrough	N/A
Discrete Sample Time	Yes
RT-LAB XHP Support	Yes
Work Offline	Yes

ARTEMiS User Documentation

ARTEMiS Transformer with Switched Saturable Core