Overview and description of the Switch-level GDS oversampling feature in Typhoon HIL
Control Center. Switch-level GDS oversampling is designed to compensate all GDS transitions within one
simulation step, in contrast to global GDS oversampling.
Switch-level GDS oversampling is implemented at component level. Check Table 1 to see which components support
Switch-level GDS oversampling. While most models works well with Global GDS oversampling, those models which have a high switching frequency
and where more than one GDS transition can happen during one simulation step should be
simulated using Switch-level GDS oversampling. Typical examples are Dual-Active-Bridge and
Resonant converter applications.
Note: If Switch-level GDS oversampling is enabled in a
component that supports it, Global GDS oversampling will be ignored for all components in the
same sub-circuit.
Note: Switch-level GDS oversampling does not support short circuit mode operation.
Table 1. Converters that supports Switch-level GDS oversampling
Converters that supports Switch-level GDS
oversampling
Converter name
Weight
IGBT Leg
1
Boost
1
The working principle of Switch-level GDS oversampling is explained using an IGBT Leg
example. As mentioned earlier, Switch-level GDS oversampling is designed to compensate all GDS
transitions within one simulation step. This is done in the following way:
Average duty cycle for every controllable switch is calculated at the simulation step
level. Because of that, all transitions will be compensated. In Figure 1 you can see two gate drive
signals whose values are changed during one simulation step. Also, you can see how the
average duty cycle changes for both signals. These average duty cycle values are fed into
the converter. The duty cycle will be calculated very precisely thanks to a small GDS
sampling period. Check GDS oversampling for more details.
The converter receives information about duty cycles of the gate drive signals, and
then this information is used to calculate the converter’s output. The converter is
modelled using controlled voltage and current sources. Figure 2 shows the model of an IGBT
Leg component which uses Switch-Level GDS oversampling. Voltage and current sources are
controlled by average GDS duty cycles. Since averaging is done at the simulation step
level and the simulation step period is small in comparison to the PWM period, the switching
ripple will be preserved. Since diodes are present in the model, the component
supports discontinuous conduction mode.
Figure 3 shows a model that
includes an IGBT Leg that uses Switch-level GDS oversampling, while Figure 4 shows a comparison of
results observed from this model with the reference results that are observed with the offline
solver. You can see that a difference occurs in the moments when the GDS is changed, but it is
obvious that the converter successfully compensates an error that would be present due to
sampling error in the case when Switch-level GDS oversampling is not used. Also, it is
important to mention that due to algorithm complexity, Switch-level GDS oversampling
introduces a delay of one simulation step between the GDS inputs and the states outputs. That
can be observed from the results, as it is obvious that L_SL_gds_ovs is delayed by one
simulation step relative to L_reference.
Figure 5 shows a model of the
Dual-Active-Bridge converter. The switching frequency is set to 80 kHz, while the simulation
step is set to 0.5 microseconds. This model is simulated using the Switch-level GDS oversampling
feature. Figure 6 shows
results observed from the simulation. As you can see, observed results are as expected and all
waveforms have their expected shapes. So, it is possible to precisely simulate a DAB converter
if Switch-level GDS oversampling is used, even in the case when the switching frequency is
relatively large.
GDS Oversampling frequency and minimum timestep
The GDS Oversampling resolution is defined by the IO Timing of the
device. This means it can be as high as 6.25 ns for
HIL402, 602+, and 604 devices, and 3.5 ns for HIL404 and HIL606 devices.