SimPowerSystems

Zigzag Phase-Shifting Transformer

Implement a zigzag phase-shifting transformer with a configurable secondary winding connection

Library

Elements

Description

The Zigzag Phase-Shifting Transformer block implements a three-phase transformer with a primary winding connected in a zigzag configuration and a configurable secondary winding. The model uses three single-phase, three- winding transformers. The primary winding connects the windings 1 and 2 of the single-phase transformers in a zigzag configuration. The secondary winding uses the windings 3 of the single phase transformers, and they can be connected in one of the following ways:

• Y
• Y with accessible neutral
• Grounded Y
• Delta (D1), delta lagging Y by 30 degrees
• Delta (D11), delta leading Y by 30 degrees

Note    The D1 and D11 notations refer to the following clock convention. It assumes that the reference Y voltage phasor is at noon (12) on a clock display. D1 and D11 refer respectively to 1 PM (lagging Y by -30 degrees) and 11 AM (leading Y by +30 degrees).

If the secondary winding is connected in Y, the secondary phase voltages are leading or lagging the primary voltages by the Phi phase angle specified in the parameters of the block. If the secondary winding is connected in delta (D11), an additional phase shift of +30 degrees is added to the phase angle. If the secondary winding is connected in delta (D1), a phase shift of -30 degrees is added to the phase angle.

The block takes into account the connection type you have selected and the icon of the block is automatically updated. An output port labeled N is added to the block if you select the Y connection with accessible neutral for the secondary winding.

The saturation characteristic, when activated, is the same as the one described for the Saturable Transformer block.

Dialog Box and Parameters

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 nominal voltage and phase shift

The phase-to-phase nominal voltage, in volts RMS, and the phase shift, in degrees, for the secondary winding of the transformer.

Secondary winding (abc) connection

The winding connection for the secondary winding.

Winding 1 (zigzag): [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 (zigzag): [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): [R1 L1]

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.

Saturable core

If selected, implements a saturable core.

Magnetization resistance Rm

This parameter is visible only if the Saturable core check box is selected.

The magnetization resistance Rm, in p.u, when the saturation is simulated.

Magnetizing branch: [Rm(p.u.) Lm(p.u.)]

The Magnetizing branch parameter is not visible in the dialog box if the Saturable core check box is selected.

The magnetization resistance Rm and inductance Lm, in p.u., when the saturation is not simulated.

Saturation characteristic

This parameter is visible only if the Saturable core check box is selected.

The saturation characteristic for the saturable core. Specify a series of current/ flux pairs (in p.u.) starting with the pair (0,0).

Measurements

Select Winding voltages to measure the voltage across the winding terminals of the Three-Phase Transformer block.

Select Winding currents to measure the current flowing through the windings of the Three-Phase Transformer block.

Select Fluxes and excitation currents (Im + IRm) to measure the flux linkage, in volt-seconds (V.s), and the total excitation current including iron losses modeled by Rm (for saturable transformers only).

Select Fluxes and magnetization currents (Im) to measure the flux linkage, in volt-seconds (V.s), and the magnetization current, in amperes (A), not including iron losses modeled by Rm (for saturable transformers only).

Select All measurements (V, I, Flux) to measure the winding voltages, currents, magnetization currents, and the flux linkages.

Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurements list box of the Multimeter block, the measurements are identified by a label followed by the block name.

The labels used in the Multimeter are as follows.

Measurement	Label
Phase voltages of primary (zigzag)	UA:, UB:, UC:
Phase currents of primary (zigzag)	IA:, IB:, IC:
Phase voltages of secondary (Y, Yn or Yg)	Uan:, Ubn:, Ucn: or Uag:, Ubg:, Ucg:
Phase voltages of secondary (delta)	Uab:, Ubc:, Uca:
Phase currents of secondary (Y, Yn, or Yg)	Ian:, Ibn:, Icn: or Iag:, Ibg:, Icg:
Phase currents of secondary (delta)	Iab:, Ibc:, Ica:
Fluxes	Flux_a:, Flux_b:, Flux_c:
Excitation currents	Iexc_a:, Iexc_b:, Iexc_c:
Magnetization currents	Imag_a:, Imag_b:, Imag_c:

Example

See the help text of the power_48pulsegtoconverter demo.

In this model, a 48-pulse GTO converter is built with four Three-Level Bridge blocks and four Zigzag Phase-Shifting Transformer blocks. Harmonic neutralization is obtained by use of appropriate phase shifts introduced by the Zigzag connections (+7.5/-7.5 degrees) and of secondary winding connections (Y or Delta).

See Also

Multimeter, Three-Phase Transformer (Three Windings)

Voltage Measurement

SimPowerSystems Command Reference