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

Control and Measurements/Pulse & Signal Generators

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

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.

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

`Third harmonic`

,`Flat top`

, or`Min-Max`

.

`Uref`

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

`Uref*`

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

Sample Time | Inherited |

Scalar Expansion | No |

Dimensionalized | Yes |

The `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,
at the MATLAB^{®} command prompt, enter

Ts = 0

`Continuous`

before starting the
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