# Overmodulation

Add third harmonic or triplen harmonic zero-sequence signal
to three-phase signal

## Library

Control and Measurements/Pulse & Signal Generators

## Description

The Overmodulation block increases the linear region of a three-phase
PWM generator by adding a third harmonic or triplen harmonic zero-sequence
signal *V*_{0} to
the three-phase original reference signal U_{ref}.
This zero-sequence signal does not appear in the line-to-line voltages.

A modulation index of up to 1.1547 (exact value = 2/sqrt(3))
can be used without pulse dropping.

The Overmodulation block implements three overmodulation techniques:

The Third Harmonic overmodulation technique. In this
technique the third-harmonic signal V0 subtracted from the original
signal is calculated as

$${V}_{0}=\frac{\left|U\right|}{6}\times \mathrm{sin}\left[3\cdot (wt+\angle U)\right]$$

The Flat Top overmodulation technique. In this technique
the portion of the three-phase input signal exceeding values +/−1
is computed. The three resulting signals are then summed and removed
from the original signal U_{ref}. The resulting
modified signal U_{ref}* is therefore a flat-top
three-phase signal that contains zero-sequence triplen-harmonics.
The block outputs a value between −1 and 1.

The Min-Max overmodulation technique. In this technique
the minimum and maximum values of the three components of input signal
U_{ref} are summed and divided by two, and then
subtracted from the input signal. The resulting modified signal U_{ref}*
also contains zero-sequence triplen-harmonics. The block outputs a
value between −1 and 1.

## Dialog Box and Parameters

**Overmodulation type**Select the overmodulation technique you want to apply to the
Uref signal: `Third harmonic`

, ```
Flat
top
```

, or `Min-Max`

.

## Inputs and Outputs

`Uref`

The three-phase reference signal of three-phase PWM generator.

`Uref*`

The overmodulated three-phase signal of three-phase PWM generator.

## Characteristics

Sample Time | Inherited |

Scalar Expansion | No |

Dimensionalized | Yes |

## Example

The `power_OverModulation`

`power_OverModulation`

example
compares the three overmodulation techniques implemented in the Overmodulation
block. Choose the overmodulation technique (type 1, 2, or 3 on the
first input of the Multiport Switch) and run the simulation. Observe
the resulting waveforms in Scope 1.

The model sample time is parameterized with variable Ts (default
value of 5e-6). To run a continuous simulation, specify Ts = 0 in
the MATLAB Command Window and change the **Simulation type** parameter
of the Powergui block to `Continuous`

before
starting the simulation.