Modulation Strategies for 3phase 2Level Voltage Source Inverters
For 3phase voltage source converters, to increase the DC voltage utilization (i.e. boost the output AC voltage) or reduce the switching losses, a zerosequence reference can be inserted in the modulation scheme provided the neutral point of the 3phase system is floating.
info
Modulation depth has a maximal value of 1 in Sine modulation and \sqrt{2/3} \approx 1.15 for other modulation strategies which add a third harmonic component.
This example presents the best of these modulation strategies  in terms of linear range and / or harmonic distortion  which can be easily implemented with Ccode or control blocks.
The V_{kO} phase voltage can be given by the equation below, where k = 1, 2, 3:
The V_{NO} voltage is managed with a zero sequence reference voltage.
Thus, the zero sequence reference voltage V_{off} is added to each phase reference V_{ref_k}:
Continuous modulation strategies
Sine modulation (Sine PWM)
With this modulation strategy, the maximum modulation index m_a is equal to 1.
Thirdharmonic injection (THIPWM)
This method adds a sinusoidal zero sequence voltage at threetimes the fundamental frequency^{1}. This example proposes the implementation of the 1/6 coefficient thirdharmonic injection.
Space vector modulation (SVM)
This modulation strategy is one of the most popular overmodulation methods. It directly defines a sequence of different switching states to follow the complex vector voltage of the threephase reference system.
The switching pattern of a symmetrical sequence has been implemented in the Ccode block.
Caution
It is currently recommended to run this block with the fixed timestep to avoid missing any switching event.
Space vector modulation "carrier based" (SVPWM)
This modulation strategy offers a similar pattern as the space vector modulation and can be shown as a triangleintersection or carrierbased implementation of the conventional Space vector modulation ^{2}, ^{3}.
It is also known as the MIN MAX modulation strategy due to the computation of the zerosequence:
Tip
To get exactly the same swithing pattern as with the conventional SVM, the sampling time of the Ccode block which computes the offset voltage must be set at the switching period of the carrier.
Discontinuous modulation strategies
DPWM min
In this strategy, each phase does not switch within 120° of the fundamental period and the output is clamped at the negative dc bus voltage. As consequence, the switches connected to the negative dc bus voltage reduce their switching losses.
DPWM max
In this strategy, each phase does not switch within 120° of the fundamental period and the output is clamped at the positive dc bus voltage. As consequence, the switches connected to the positive dc bus voltage reduce their switching losses.
DPWM1
In this case the phase leg is clamped 30° symmetricaly from maximal voltage. This method has low harmonic distortion characteristics. The zerosequence is extracted from the following equations:
References

G.Buja and G. Indri. “Improvement of pulse width modulation techniques”. Archiv fur Elektrotechnik, 57, pages 281289, 1975. ↩

A.M.Hava, “Carrier based PWMVSI drives in the overmodulation region”. Vol. 1. University of Wisconsin–Madison, 1998. ↩

Ke. Zhou and D. Wang, "Relationship Between SpaceVector Modulation and ThreePhase CarrierBased PWM: A Comprehensive Analysis", IEEE Transactions On Industrial Electronics, Vol. 49, No. 1, February 2002. ↩