Tap-Changing Transformer

Single-phase tap-changing transformer

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Libraries:
Simscape / Electrical / Passive / Transformers

Description

The Tap-Changing Transformer block represents a single-phase tap-changing transformer. You can vary the turns-ratio of the transformer during the simulation using the control input.

Use this component to regulate or change the output voltage of a linear transformer during a simulation. To model the effects of saturation, consider using the Nonlinear Transformer block.

Operating Principle

Use the control input c to change the tap position of the transformer.

• Increase c above the Control threshold, t, to increase the tap position p by one.

• Decrease c below the negative of the Control threshold to decrease the tap position p by one.

This figure shows the tap-response to a control input.

In the diagram:

• N₀ is the nominal number of turns for the tap-changer winding.

• δ is the percent change in turns per tap position step. Specify this value using the Change per tap (%) parameter.

• p_min and p_max are the minimum and maximum allowable tap indices. Specify these values with the Minimum tap index (nominal=0) and Maximum tap index (nominal=0) parameters.

To select the tap-changer winding, use the Tap-changer location parameter. The overall turns ratio, n, depends on this location:

• Primary

  $$n=\frac{N_p(N_0,\delta ,p)}{N_s}=n_0\left(1+\frac{\delta p}{100}\right)$$

• Secondary

  $$n=\frac{N_p}{N_s(N_0,\delta ,p)}=n_0{\left(1+\frac{\delta p}{100}\right)}^{-1}$$

where n₀ is the nominal turns ratio for the transformer.

Equivalent Circuit

The equivalent circuit is shown in the diagram.

Here:

• R_p and R_s are the primary and secondary series resistances, respectively. Changes in the tap position affect these values.

• L_lp and L_ls are the primary and secondary leakage inductances, respectively. Changes in the tap position affect these values.

• R_m and M are the magnetization resistance and inductance, respectively. Changes in the tap position affect these values.

• n is the turns ratio of the transformer.

• G_p and G_s are the primary and secondary leakage conductances, respectively. Changes in the tap position do not affect these values.

Examples

Tap-Changing Transformer for Automatic Voltage Regulation

Use a single-phase tap-changing transformer to control the voltage across an RLC load. The system contains an AC voltage source that generates a 60 Hz sine wave (located on the left-hand side of the circuit). The root-mean-square value for the voltage generated by this source is 120 V (reference voltage).

• Open Model

Ports

Conserving

1+ — Line 1 positive terminal

electrical

Electrical conserving port associated with the positive terminal of line 1.

1- — Line 1 negative terminal

electrical

Electrical conserving port associated with the negative terminal of line 1.

2+ — Line 2 positive terminal

electrical

Electrical conserving port associated with the positive terminal of line 2.

2- — Line 2 negative terminal

electrical

Electrical conserving port associated with the negative terminal of line 2.

c — Control input

physical

Input physical signal that specifies the input control value.

Parameters

Nominal

Turns ratio (primary/secondary) — Turns ratio

1 (default) | positive number

Turns ratio of the transformer in the nominal tap position. The turns ratio is defined as the primary number of turns divided by the secondary number of turns.

Primary leakage inductance — Line 1 leakage inductance

1e-6 H (default) | positive number

Leakage inductance of the primary winding.

Secondary leakage inductance — Line 2 leakage inductance

1e-6 H (default) | positive number

Leakage inductance of the secondary winding.

Core-loss resistance — Mutual resistance

1e6 Ohm (default) | zero or positive number

Mutual resistance of the transformer.

Magnetization inductance — Magnetization inductance

100e-6 H (default) | positive number

Magnetization inductance of the transformer.

Primary series resistance — Line 1 series resistance

0 Ohm (default) | zero or positive number

Series resistance of the primary winding.

Secondary series resistance — Line 2 series resistance

0 Ohm (default) | zero or positive number

Series resistance of the secondary winding.

Primary leakage conductance — Line 1 leakage conductance

0 1/Ohm (default) | zero or positive number

Leakage conductance of the primary winding. Set this value to be nonzero for achieving numerical convergence in some circuit topologies.

Secondary leakage conductance — Line 2 leakage conductance

0 1/Ohm (default) | zero or positive number

Leakage conductance of the secondary winding. Set this value to be nonzero for achieving numerical convergence in some circuit topologies.

Tap

Tap-changer location — Tap-changer winding

Primary (default) | Secondary

Specify whether the tap-changer is on the primary or secondary winding.

Minimum tap index (nominal=0) — Minimum tap position

-5 (default) | zero or negative integer

Minimum allowable position of the tap-changer.

Maximum tap index (nominal=0) — Maximum tap position

5 (default) | zero or positive integer

Maximum allowable position of the tap-changer.

Change per tap (%) — Tap change step

1 % (default) | positive number

Percent change in the number of turns per tap position step of the tap-changer winding. Set this value such that the absolute percent change at the minimum and maximum tap indices is less than 100 %.

Control threshold — Shift threshold

0.5 (default)

Control value at which the tap changes position. To lower the tap position, apply a control signal c smaller than the negative of this value. To increase the tap position, apply a control signal c greater than this value.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a