The PWM average generator is a pulse generator averaged over the time step of the simulation. It uses an interpolation technique to calculate the transition moment within a sample time of the model.

Note: This component should be used with the 2-Level Converter (Switching Function). To properly initialize this component select Solve Control inputs before available in the Advanced tab in the Simulation Settings.

Mask and Parameters

Parameter Name	Description	Unit	Variable = {Possible Values}
Description	Use this field to add information about the component		Description = {'string'}
Use signal as PWM carrier frequency	When enabled the component uses the frequency input signal to calculate the carrier. Otherwise, the component uses the PWM carrier frequency parameter to calculate the carrier		use_sig_Fc = { [0, 1] }
PWM carrier frequency	Frequency of the triangular carrier signal	Hz	FrequencyCarrier = { [0, 1e12] }
PWM carrier initial phase	Initial phase of the carrier	°	InitialPhase = { [0, 360] }
PWM dead time	Deadtime protection to avoid adjacent arms to close simultaneously. The Deadtime value must no be greater than the time step (Ts) of the simulation	s	Deadtime = { [0, Ts] }

Inputs, Outputs and Signals Available for Monitoring

Inputs

Name	Description
Vref	Vectorized reference signal containing the phase-ground voltages of the AC side (Va, Vb et Vc).
Fc	Frequency signal used to calculate the carrier.

Outputs

Name	Description
P	Vectorized signal containing six firing pulses to control the converter.

Sensors

Name	Description	Unit
Va	Reference voltage signal from phase A.	V
Vb	Reference voltage signal from phase B.
Vc	Reference voltage signal from phase C.
Fc	Frequency signal used to calculate the carrier.	Hz
P1	Signal containing a firing pulse to control Q1 (phase A upper arm of the converter)
P2	Signal containing a firing pulse to control Q2 (phase A lower arm of the converter)
P3	Signal containing a firing pulse to control Q3 (phase B upper arm of the converter)
P4	Signal containing a firing pulse to control Q4 (phase B lower arm of the converter)
P5	Signal containing a firing pulse to control Q5 (phase C upper arm of the converter)
P6	Signal containing a firing pulse to control Q6 (phase C lower arm of the converter)
Carrier	Triangular carrier signal.

Additional Information

The interpolation technique of the averaged pulse generator needs to know when a transition from high-to-low or low-to-high occurs within a sample time, allowing this component to provide the timing for these transitions. The use of this type of PWM in addition to the converter modeled using switching function allows simulations with a much larger sample time while keeping high fidelity during the simulation. The figure below shows the operating principle of this model for a carrier frequency (Fc) of 2 kHz and a duty cycle of 0.8. The time step is 50 μs.

Operation principle

The generator emits a pulse value based on a carrier-based modulation technique (natural sampling) and the time step of the simulation. If a transition occurs within a sample time, the generator outputs a pulse value representing the time ratio (a value between 0 and 1) for the ON state over the sample time. For example, in the figure above, the pulse value generated at 0.25 means that the 0 to 1 transition occurred at 0.25 · Ts seconds (it was ON during 25% of the model time step). The offset is represented by the dotted area in brown. For the 1 to 0 transition, the generator provides a value of 0.75, which means that the pulse was active for 75% of the computing time (it entered the OFF state 0.75 · Ts seconds after the previous sample time).

Model operation when the Use signal as PWM carrier frequency option is enable

If the Use signal as PWM carrier frequency option is enabled, the component uses the frequency input signal to calculate the carrier. During the first step of the simulation, the component read the value of the frequency signal Fc and uses the phase initial parameter value in the form to calculate the initial interpolation of the carrier signal. By the end of the step, the component keeps in memory the value of the frequency read in the first step.

During the next step, once the component has calculated the carrier signal, if there is not a change in the frequency in the step, the component does not recalculate the carrier signal. If there is a change in frequency, the component, therefore, recalculates its carrier signal according to the new frequency Fc.

The Figure below shows the operation of the component when the Use signal as PWM carrier frequency option is enable and disable.

Block diagram of the PWM Average Generator

Limitations

This component should be used with the 2-Level Converter (Switching Function).

To obtain precision, the time step of the simulation must not be more than 1/10 of the period the carrier (1 / Fc).

The Deadtime value must no be greater than the time step (Ts) of the simulation.

HYPERSIM Documentation

PWM Average Generator for 2-Level Converter (Switching Function)